La Surface Research Articles

149 Automated analysis of atrial ablation-scar using delayed-enhanced cardiac MRI

Introduction Visualisation of the ablation-related atrial scar using delayed-enhanced MRI (DE-MRI) may reveal important underlying causes for atrial fibrillation (AF) recurrence following ablation. In order to develop and objective method for delineating ablation-scar we compared pre and post DE-MRI after Cryo-balloon lesion on the basis that a more predictable lesion set would be created for validation. Methods and Results 12 patients undergoing cryoablation for PAF were enrolled in the study, and underwent pre-ablation DE-MRI scans. Pulmonary vein isolation (PVI) was confirmed in all patients at the end of the cryoablation procedure using a circular mapping catheter. Additional ablation by RF or Freezer Max was required to achieve PVI in 59%. No ablation was performed in any region other than the PV ostia. Post-ablation DE-MRI was performed at 3 months. An automatic segmentation of the LA was produced with custom software from the MRA sequence. The preablation and postablation free breathing late gadolinium enhanced sequence was registered to the MRA and the maximum intensity within the LA wall was projected onto the post ablation LA surface. The blood pool was identified automatically using custom software as the region 1 cm inside the wall of the LA, and its mean (BPM) and SD used as a baseline. To identify a universal threshold for scar, regions of brightest myocardium were initially selected in pre and post ablation MRIs. The brightest regions were 1.9±1.2 vs 8.7±3.1 SDs above the BPM in pre-and post-ablation MRIs respectively (p=0.001). A threshold of 5 SDs above the BPM was therefore programmed into our custom software to identify regions of scar for all patients. The ostial regions were defined as extending 1 cm both proximal and distal to the PV–LA junction, and selected manually for left and right sided veins prior to scar projection. (See Abstract 149 figure 1). The scar proportion within these regions was calculated using commercially available software ITK-SNAP. Total LA scar proportion was 0.2±0.02% vs 6.3±0.75% in pre and post ablation scans respectively. The increase in scar seen in the PV ostia was 24.6±1.38% compared with 2.6±1.28% in the rest of the LA (p=0.01) (See Abstract 149 figure 2). Conclusion We have demonstrated the feasibility an objective, automated method of DE-MRI analysis of left atrial ablation-scar. This technique will now need to be validated against clinical outcomes.

Atomic and electronic surface structures of dopants in oxides: STM and XPS of Nb- and La-doped SrTiO3(001)

High resolution X-ray photoelectron spectroscopy (XPS) was performed on the (001) surfaces of Nb-doped and La-doped single crystals of SrTiO${}_{3}$. For the Nb-doped samples the XPS results demonstrate that the fraction of Ti${}^{3+}$ ions increases with increasing Nb dopant concentration. The Nb dopants are shown to be in a $5+$ ionization state. Atomic resolution scanning tunneling microscopy (STM) images of the 0.7 at.% Nb-doped SrTiO${}_{3}$(001) surface show that Nb-dopant atoms can be imaged on the surface as bright four-point square clusters. No evidence of Nb segregation to the (001) surface was found under ultrahigh vacuum (UHV) annealing. However, UHV annealing of the 0.7 at.% La-doped SrTiO${}_{3}$(001) samples at 1400$ {}^{\ifmmode^\circ\else\textdegree\fi{}}\mathrm{C}$ for 1 h resulted in La surface segregation as determined by Auger electron spectroscopy. STM on these samples shows that the segregated La results in La-rich linear surface structures.

Gravity-driven Lyα blobs from cold streams into galaxies

We use high-resolution cosmological hydrodynamical AMR simulations to predict the characteristics of La emission from the cold gas streams that fed galaxies in massive haloes at high redshift. The La luminosity in our simulations is powered by the release of gravitational energy as gas flows from the intergalactic medium into the halo potential wells. The UV background contributes only <20% to the gas heating. The La emissivity is due primarily to electron-impact excitation cooling radiation in gas ~2x10^4K. We calculate the La emissivities assuming collisional ionisation equilibrium (CIE) at all gas temperatures. The simulated streams are self-shielded against the UV background, so photoionisation and recombination contribute negligibly to the La line formation. We produce theoretical maps of the La surface brightnesses, assuming that ~85% of the La photons are directly observable. We find that typical haloes of mass Mv~10^12-13 Msun at z~3 emit as La blobs (LABs) with luminosities 10^43-44 erg/s. Most of the La comes from the extended narrow, partly clumpy, inflowing, cold streams that feed the growing galaxies. The predicted LAB morphology is therefore irregular, with dense clumps and elongated extensions. The linewidth is expected to range from 10^2 to more than 10^3 km/s with a large variance. The typical La surface brightness profile is proportional to r^-1.2 where r is the distance from the halo centre. Our simulated LABs are similar in luminosity, morphology and extent to the observed LABs, with distinct kinematic features. The predicted La luminosity function is consistent with observations, and the predicted areas and linewidths roughly recover the observed scaling relations. This mechanism for producing LABs appears inevitable in many high-z galaxies. Some of the LABs may thus be regarded as direct detections of the cold streams that drove galaxy evolution at high z.

Agonist-selective Dynamic Compartmentalization of Human Mu Opioid Receptor as Revealed by Resolutive FRAP Analysis

Techniques for analyzing the membrane diffusion of molecules are the most promising methods for investigating the compartmentalization of G-protein-coupled receptors, particularly as relevant to receptor signaling processes. Here, we report fluorescence recovery after photobleaching (FRAP) measurements performed at variable spot radius for human mu opioid (hMOP) receptors on SH-SY5Y neuroblastoma cells in the presence of ligands. Although an antagonist did not affect the behavior of the receptors compared with the basal state, two different agonists, DAMGO and morphine, caused markedly different changes to receptor diffusion. Like receptors in the absence of ligand, receptors bound to morphine exhibited diffusion confined to joined semipermeable domains, but with smaller domain size and diffusion coefficient. This effect was inhibited by pertussis toxin, strongly suggesting that this dynamic behavior is associated with early steps of signaling. In the presence of DAMGO, half of the receptors displayed free long-range diffusion and the other half were confined to smaller isolated domains. Hypertonic sucrose buffer suppressed this effect, which we attribute to receptor entry into clathrin-coated pits. It is likely that the observation of distinct receptor dynamics in the presence of DAMGO and morphine involves the agonist-selective phosphorylation of the receptor.

“One Single Mystery of Persons and Objects”: The Erotics of Fragmentation in au Hasard Balthazar

Cette analyse détaillée d’Au hasard Balthazar (1966) de Robert Bresson explore la préoccupation du film pour l’immanence des sensations, inversant ainsi deux interprétations dominantes pour lesquelles le travail du cinéaste se comprend en termes de transcendance ascétique ou par le biais du formalisme. La lecture examine l’emploi du fragment en posant que la relation de la partie au tout, telle qu’elle est mise en place par le film, trace la voie d’un engagement affectif qui figure plutôt que représente l’érotique. Cette figuration permet l’émergence d’un genre différent de plaisir du texte qui ne repose ni sur l’identification au personnage ni sur l’absence de structure formelle déterminée, mais qui est issue de la surface sensuelle même du film et de la texture de son indétermination.

The role of La surface chemistry in the passivation of Ge

The oxidation of a Ge surface by molecular oxygen in the presence of ultrathin La, Al, and Hf layers was examined by in situ x-ray photoelectron spectroscopy. Upon exposure to O2, clean bare Ge and Hf-covered or Al-covered Ge surfaces show no Ge–O bond formation. On the contrary, a La-covered Ge surface strongly reacts with O2 forming a stable germanate LaGeOx compound. This has a beneficial side effect for the interface because the formation of volatile GeO is suppressed, resulting in the good passivating properties of LaGeOx. The photoemission results are correlated with the oxygen density differences in the corresponding oxides.

La2Cu0.8Co0.2O4+δ by Pechini Method

Cobalt-doped lanthanum cuprates of the type La2Cu1-xCoxO4 are Ruddlesden-Popper compounds characterized by several interesting properties. In particular, thanks to the presence of copper and cobalt, they can be utilized as catalysts in redox reactions. Moreover, from an electrical point of view, cobalt-doped lanthanum cuprates are Mixed-Electronic-Ionic-Conductors. These important characteristics could be gainfully employed in improving the Intermediate-Temperature-Solid-Oxide-Fuel-Cells electrodes performances, from both the catalytic and electrical sides. A La2.0Cu0.8Co0.2O4+δpowder was prepared by Pechini procedure. Besides the wide scan spectra, detailed spectra for the La 3d, La 4d, Cu 2p, Co 2p, O 1s and C 1s regions and related data are presented and discussed. XP analysis confirms the presence of La (III) and Cu (II); the peak shapes are consistent with a residual presence of hydroxide and carbonate species, as confirmed by the O 1s and C 1s signals. The XPS atomic composition supports this hypothesis: in fact the O/(La+Cu+Co) atomic ratio (= 1.86) is higher than the expected value (= 1.33). Also the La/(Cu+Co) atomic ratio (= 0.80) is higher than the nominal value (= 0.66) and suggests La surface segregation.

Adenosine-induced ventricular asystole or rapid ventricular pacing to enhance three-dimensional rotational imaging during cardiac ablation procedures

Rotational angiography with digital three-dimensional reconstruction (3DRA) allows per-procedural 3D imaging to facilitate cardiac ablation procedures. We developed a new approach that allows per-procedural 3D imaging of the atria and ventricles with a single C-arm rotation, combining higher 3D image quality with a lower contrast and radiation dose. Forty patients underwent 3DRA of the left atrium (LA, n = 26), right atrium (RA, n = 11), left ventricle (LV, n = 2), or right ventricle (RV, n = 1) during ablation procedures performed under general anaesthesia. Contrast agent (60 +/- 12 mL) was diluted and injected directly in the chamber of interest, during adenosine-induced ventricular asystole (n = 31) or rapid RV pacing (n = 9, atrial imaging only) to reduce cardiac motion artefacts and enhance contrast opacification during rotational imaging. Reconstructed 3D data sets were graded according to predefined quality criteria (n = 40) and quantitatively compared with cardiac computed tomography (CT) (LA, n = 14). Adenosine-induced ventricular asystole and rapid pacing both allowed a sustained and homogeneous contrast opacification of target cardiac chambers, resulting in useful 3D data sets in 39 of 40 (98%) patients. Moreover, it was possible to achieve 'good' or 'optimal' 3D image quality in the majority of patients (adenosine: 61%, pacing 78%, P = 0.69). When compared with rapid pacing, the total elimination of cardiac motion artefacts with adenosine more frequently resulted in 'optimal' 3D image quality (42% vs. 11%, P = 0.01) and added the possibility for single-rotation 3D imaging of the ventricles. Quantitative analysis showed an excellent agreement between pulmonary vein diameters measured on cardiac CT and 3DRA images. Integration of 3DRA-based LA surfaces with real-time fluoroscopy was easy and highly accurate. Adenosine-induced ventricular asystole or rapid ventricular pacing allow acquisition of 3DRA with an excellent direct contrast opacification of any cardiac chamber and a reduction of cardiac motion artefacts, resulting in high-quality per-procedural 3D imaging with a single C-arm rotation.

Effect of La Surface Coatings on Oxidation Behavior of Aluminum Alloy/SiCp Composites

The oxidation behavior of aluminum-matrix-composites (A3 xx.x/SiCp) has been studied after La deposition with conversion and electrolytic treatments. Kinetics data of the corrosion process were obtained from gravimetric tests performed at different temperatures (350, 425 and 500°C). The nature of the corrosion products and the influence of the microstructure on the morphology and growth of the oxidation layer were analyzed by scanning-electron and atomic-force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The extent of oxidation degradation in untreated composites was characterized by a phenomenon of oxidation preferentially localized in matrix/SiCp interfaces favoring MgO formation. La coatings favored a homogeneous oxidation of the composite surface favoring MgAl2O4 spinel formation. In addition, this oxide increased the surface hardness of materials.

The biology of vernix caseosa

The biology and physical properties of the uniquely human skin cream 'vernix caseosa' are discussed. This material coats the foetal skin surface during the last trimester of gestation and provides multiple beneficial functions for the foetus and newborn infant. Vernix has a complex structure similar to stratum corneum but lacks lipid lamellae and is more plastic due to the absence of desmosomal constraints. In utero, vernix is made in part by foetal sebaceous glands, interacts with pulmonary surfactant, detaches into the amniotic fluid, and is swallowed by the foetus. At the time of birth, vernix has a remarkably constant water content approximating 80%. Postnatally, vernix is simultaneously a cleanser, a moisturizer, an anti-infective, and an anti-oxidant. Vernix facilitates acid mantle development and supports normal bacterial colonization. Its hydrated cellular structure and unusual lipid composition provide a 'best' solution for the needs of the foetus and newborn, not least of which is the attraction of caregivers. Vernix is an important natural biomaterial of potential interest to cosmetic scientists, and other disciplines involved in product development and therapies targeting the complex interface between the stratum corneum and a changing terrestrial environment.

Bayesian spatial analysis and disease mapping: tools to enhance planning and implementation of a schistosomiasis control programme in Tanzania

To predict the spatial distributions of Schistosoma haematobium and S. mansoni infections to assist planning the implementation of mass distribution of praziquantel as part of an on-going national control programme in Tanzania. Bayesian geostatistical models were developed using parasitological data from 143 schools. In the S. haematobium models, although land surface temperature and rainfall were significant predictors of prevalence, they became non-significant when spatial correlation was taken into account. In the S. mansoni models, distance to water bodies and annual minimum temperature were significant predictors, even when adjusting for spatial correlation. Spatial correlation occurred over greater distances for S. haematobium than for S. mansoni. Uncertainties in predictions were examined to identify areas requiring further data collection before programme implementation. Bayesian geostatistical analysis is a powerful and statistically robust tool for identifying high prevalence areas in a heterogeneous and imperfectly known environment.

Enhanced corrosion resistance of A3xx.x/SiCp composites in chloride media by La surface treatments

The influence of silicon carbide particles (SiCp) proportion and matrix composition of aluminium metal matrix composites (A3xx.x/SiCp) modified by lanthanum-based conversion or electrolysis coating was evaluated in 3.5 wt% NaCl aerated solution. The intermetallic compounds were preferentially covered by lanthanum-based conversion coatings obtained by immersion in 50 °C solution of La(III) salt, and the intermetallic compounds, SiCp and aluminium matrix were covered by lanthanum electrolysis treatment. The corrosion process was studied on the basis of gravimetric tests and electrochemical impedance spectroscopy (EIS) during immersion in 3.5 wt% NaCl aerated solution. The composition of both La coating and corrosion products was analyzed before and after accelerated testing, by scanning electron microscopy (SEM), atomic force microscopy (AFM), low-angle X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to determine the influence of surface microstructural changes on corrosion behaviour during exposure to the corrosive environment. The corrosion process was more influenced by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement. Both lanthanum treated surfaces presented better behaviour to chloride solution corrosion than original composite surfaces without treatment; however, electrolysis afforded a higher degree of protection than the conversion treatment because the coating was more extensive.

GAS SLAG REACTION KINETICS IN SLAG CLEANING OF COPPER SLAGS

Measurements of the rate constant of CO2 dissociation on the surface of molten FexO-SiO2-Al2O3-Cu2O slag have been made by using the 13CO2-CO isotope exchange technique as a function of temperature and imposed equilibrium CO2/CO ratio. It is shown that the apparent first-order rate constant remains fixed with Cu2O content from 1 to 10 wt% at higher oxygen potentials. The rate constant becomes approximately 2 times higher after metallic copper is reduced from the slag. The effect of temperature in the range from 1200 to 1450 °C on the rate constant was also studied and the activation energy was 190 kJ/mole for slag of composition 60FexO-30SiO2-10Al2O3. In the presence of Cu metal, the activation energy was reduced to122 kJ/mole.On a effectué des mesures de la constante de vitesse de dissociation du CO2 à la surface de scorie de FexO-SiO2-Al2O3-Cu2O fondue en utilisant la technique d’échange de l’isotope 13CO2-CO en fonction de la température et du rapport d’équilibre imposé de CO2/CO. On montre que la constante de vitesse apparente du premier ordre demeure fixe pour une teneur en Cu2O de 1 à 10% en poids, aux potentiels d’oxygène plus élevés. La constante de vitesse devient approximativement 2 fois plus élevée après réduction du cuivre métallique à partir de la scorie. On a également étudié l’effet de la température sur la constante de vitesse dans la gamme de 1200 à 1450 °C. L’énergie d’activation était de 190 kJ/mole pour la scorie de composition 60FexO-30SiO2-10Al2O3. En présence de métal Cu, l’énergie d’activation était réduite à 122 kJ/mole.

Effect of La surface treatments on corrosion resistance of A3 xx. x/SiC p composites in salt fog

The influence of the SiC p proportion and the matrix concentration of four aluminium metal matrix composites (A360/SiC/10p, A360/SiC/20p, A380/SiC/10p, A380/SiC/20p) modified by lanthanum-based conversion or electrolysis coating was evaluated in neutral salt fog according to ASTM B 117. Lanthanum-based conversion coatings were obtained by immersion in 50 °C solution of La(III) salt and lanthanum electrolysis treatments were performed in ethylene glycol mono-butyl ether solution. These treatments preferentially covered cathodic areas such as intermetallic compounds, Si eutectic and SiC p. The kinetic of the corrosion process was studied on the basis of gravimetric tests. Both coating microstructure and nature of corrosion products were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDS) and low angle X-ray diffraction (XRD) before and after accelerated testing to determine the influence of microstructural changes on corrosion behaviour during exposure to the corrosive environment. The corrosion process was more influenced by the concentration of alloy elements in the matrix than by the proportion of SiC p reinforcement. Both conversion and electrolysis surface treatments improved the behaviour to salt fog corrosion in comparison with original composites without treatment. Additionally, electrolysis provided a higher degree of protection than the conversion treatment because the coating was more extensive.

OXIDE INCLUSION DEFECTS IN Al-Si-Mg CAST ALLOYS

Oxide films on the surface of liquid aluminum alloys are entrapped in castings to form stable solid inclusions as a consequence of surface turbulence. The oxide film defects are highly damaging to aluminum alloy castings because of their nature as cracks. The oxide films or particles observed in Al-11.5Si-0.4Mg cast alloys include Al2MgO4, Al2O3, MgO and SiO2. The paper discusses the identification, main features and formation mechanisms of oxide inclusions in Al-11.5Si-0.4Mg cast alloys combined with an overview of the oxide inclusions from a number of publications to summarize the central importance of oxide films in the development of the structure of Al-Si cast alloys. To produce reliable castings, the removal of oxide films from aluminum melts and the avoidance of the entrapment of oxide films during metal melting, delivering, transferring and pouring remain a great challenge for the metal casting industry.Les films d’oxyde à la surface d’alliages d’aluminium liquides sont piégés dans les moulages formant ainsi des inclusions solides et stables comme conséquence de la turbulence superficielle. Ces films d’oxyde sont extrêmement nuisibles aux moulages d’alliage d’aluminium à cause de leur nature en forme de fissures. Les films d’oxyde ou les particules observés dans les alliages moulés d’Al-11.5Si- 0.4Mg incluent Al2MgO4, Al2O3, MgO et SiO2. Ce document discute de l’identification, des principales caractéristiques et des mécanismes de formation des inclusions d’oxyde dans les alliages moulés d’Al-11.5Si-0.4Mg. On fait également une revue des inclusions d’oxydes à partir de plusieurs publications, résumant l’importance essentielle des films d’oxyde dans le développement de la structure des alliages moulés d’Al-Si. Afin de produire des moulages fiables, la suppression des films d’oxyde des bains d’aluminium ainsi que la prévention de leur piégeage lors de la fonte du métal, de la livraison, du transfert et du coulage restent un grand défi pour l’industrie de moulage du métal.

H2 dissociative adsorption on Mg, Ti, Ni, Pd and La Surfaces

We calculate the corresponding two-dimensional (2D) potential energy surfaces (PESs) for one fixed lateral H2 center of mass position and one H2 orientation on Mg(0 0 0 1), Ti(0 0 0 1) Ni(1 1 1), Pd(1 1 1) and La(0 0 0 1) surfaces within the density functional theory. From the results, on the Ti, Ni, Pd and La surfaces, the energy barriers for H2 dissociative adsorption are either small or negligible. On the other hand, on the Mg surface, a high energy barrier exists. Furthermore, we can practically explain these differences among the surfaces by considering the differences in the valence electron configurations of the substrate atoms.

Dissociation and Sticking of H2on Mg(0001), Ti(0001) and La(0001) Surfaces

We performed quantum dynamics calculations using previously obtained potential energy surfaces (PESs) for the dissociative adsorption of hydrogen molecule incident on a Mg(0001), Ti(0001), and La(0001) surface. Based on the sticking probability plots we obtained as functions of the incidence H 2 beam energy, La is the best material for hydrogen storage, followed by Ti, and then by Mg. This is due to the absence of an activation barrier in the H 2 /La(0001) system. Both H 2 /Ti(0001) and H 2 /Mg(0001) systems have activation barriers, but the H 2 /Ti(0001) system has a very small activation barrier far from the curved region of the reaction path, while the H 2 /Mg(0001) system has a high activation barrier close to the curved region along the reaction path. Our results also indicate that the sticking probability has some dependence on the vibrational state of the impending H 2 molecule for the Mg, Ti and La surfaces. The degree of dependence still varies in each metal. Vibrational effect is most observed w...

Ultrafast temporary charge transfer in pyrrolidinyl-benzonitrile and pyrrolyl-benzonitrile in the gas phase.

4-(N-pyrrolidinyl)benzonitrile and 4-(N-pyrrolyl)benzonitrile were excited by an ultrashort pulse at 270 nm to their La (S2) states and then probed by ionization at long wavelengths. Parent and fragment ion signals show components with time constants < 100 fs which we attribute to ultrafast relaxation to the Lb (S1) state. From this short time we infer a conical intersection between the Lb and La surfaces. The wave packet can branch there, one part going temporarily to a strongly displaced state. Its shift was concluded from an anisotropy observed only there. The only excited state known to have a large displacement is the charge-transfer (CT) state. The positive anisotropy indicates that the CT state belongs to the 2A species for both molecules. For pyrrolylbenzonitrile, this is in contrast to previous assignments. The anisotropy, and a coherent oscillation observed in pyrrolidinylbenzonitrile, support the idea that the amino-group twist is an important component of the CT reaction coordinate.

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Calcium Isotopic Composition of Various Reference Materials and Seawater

A compilation of δ44/40Ca (δ44/40Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF2 reference sample. The deviations in δ44/40Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between δ44/40Ca of NIST SRM 915a and seawater is defined as ‐1.88 O.O4%o (δ44/42CaNISTSRM915a/Sw= ‐0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation δ44/40CaSa/Sw=δ44/40CaSa/NIST SRM 915a ‐ 1.88 (δ44/42CaSa/Sw=δ44/42CaSa/NIST SRM 915a ‐ 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies.