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The evolution of two-dimensional (2D) islands which result from a chemo-mechanical polishing of vicinal (1, −1, 0, 2) sapphire surfaces was explored by atomic force microscopy (AFM) after annealing in air. The evolution of the surface morphology is followed after isothermal annealing (1173 K) for duration varying from 1 h to 53 h and isochronal annealing at temperatures between 1023 K

The evolution with temperature of the morphology of yttria-stabilized zirconia (100) stepped surfaces has been studied by AFM in a non-contact dynamic mode in air. The characteristics of the surface structure as the average step heights and terrace widths are determined as a function of the annealing temperature. Step formation begins around 0.43 T M (1000 °C). Step coalescence is observed above 0.50 T M (1200 °C) and leads to a stable stepped structure at 0.60 T M (1500 °C). The processes responsible for the structural evolution observed on the sample surfaces are discussed and a comparison with results obtained on Al 2 O 3 (0001) single crystal surfaces under similar experimental conditions is presented.

A vicinal (0001) alumina surface, annealed at 1500°C for 4 h in air, is studied by atomic force microscopy (AFM) at room temperature. The images show two different kinds of steps: faceted steps with a height of several nanometres, running in the [1010] direction and steps of 0.22 nm height ( c /6 steps with reference to alumina cell) which cross terraces in between faceted steps. The orientation distribution of the c /6 steps reveals two distinct directions not parallel to any low-index crystalline direction. The main values of the angle between each c /6 steps and the [1010] direction, equal to 36.5° and 52.5° respectively, alternate strictly along a terrace in between faceted steps. These c /6 steps generally appear coupled. The existence of two kinds of c /6 step orientations corresponds to different step energies due to different atomic arrangements originating from the bulk lattice of alumina. The atomic packing, responsible for angular alternation of neighbouring steps, determines the third order symmetry of c /6 step properties. Statistical analysis of step orientations and further modelling yields an angular dependence of the step energy. The anisotropy of c /6 step energy is found to be weak

Development of the morphology of vicinal (0001) surfaces of α-alumina, induced by annealing in air at 1500 °C, was studied by AFM. Our investigation shows that the resulting surface morphology depends on both the duration of thermal treatment and the surface misorientation relative to crystallographic directions. The whole vicinal surface, which is initially covered by steps of 0.21 nm height, after heating can exhibit two kinds of morphologies due to step bunching or step faceting. Step bunching occurs even after a relatively short annealing time (1 h) and is found to depend on the miscut angle. Further annealing of bunched stepped surfaces leads to the disappearance of bunching, leaving sometimes a new faceted phase. In the general case of facets, the border of faceted steps follows the [10 10] crystallographic direction, and less closely the [11 20] direction, producing zigzags. The faceting process is triggered by the step height exceeding a certain value. The origin of incubation time for the faceting process is discussed. Copyright © 2000 John Wiley & Sons, Ltd.

Evolution of the step arrangement on vicinal (0001) surfaces of an α -alumina crystal annealed for 1 h in the range of 1000–1500°C in air was investigated by atomic force microscopy. For T h 1 =0.2 nm) forms mainly parallel double-height steps. At temperatures >1200°C, steps with larger heights grow either due to direct coalescence or due to the displacement of single steps. During coalescence of steps in the whole temperature range investigated, the direction of the higher steps keeps parallel to that of the initial monosteps over hundreds of microns although it does not correspond to any low index crystalline orientation. Different mechanisms of growth of the steps are discussed. A quantitative estimation of the activation energy of one effective self diffusion process can be performed.

Background It is commonly acknowledged that asthma is exacerbated by viral infections. On the other hand, basophil infiltration of lung tissues has been evidenced postmortem in cases of fatal disease, raising the question of a possible link between these two observations. Objectives Herein, we addressed the relationship between asthma exacerbation by viral infection and basophil activation and expansion by investigating how stimulation with the dsRNA polyadenylic/polyuridylic acid [poly(A:U)] affected basophil activities and recruitment in an allergic airway inflammation model. Methods The effect of dsRNA on basophils was assessed by measuring the cytokine levels produced upon stimulation. We used an OVA-induced experimental model of allergic asthma. Airway hyperreactivity, recruitment of infiltrating cells, and cytokine production were determined in the lung of mice having received poly(A:U), as compared with untreated controls. The exacerbating effect of basophils was assessed both by adoptive transfer of poly(A:U)-treated basophils and by their in vivo depletion with Ba103 antibody. Results We found that in vitro treatment with poly(A:U) increased basophil functions by inducing TH2-type cytokine and histamine production, whereas in vivo treatment increased peripheral basophil recruitment. Furthermore, we provide the first demonstration for increased infiltration of basophils in the lung of mice suffering from airway inflammation. In this model, disease symptoms were clearly exacerbated upon adoptive transfer of basophils exposed to poly(A:U), relative to their unstimulated counterpart. Conversely, in vivo basophil depletion alleviated disease syndromes, thus validating the transfer data. Conclusions Our findings provide the first evidence for airway inflammation exacerbation by basophils following dsRNA stimulation.

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The structure of self-assembled monolayers of long n-alkane molecules deposited on an Au(111) surface has been studied by in situ scanning tunnelling microscopy at 300 K. These monolayers are formed on Au(111) either at the interface between gold and a solution of hexatriacontane (C 36 H 74 ) in tetradecane, or by ultrahigh vacuum (UHV) deposition of octatriacontane (C 38 H 78 ). At the liquid/solid interface, the monolayer consists of a close-packed arrangement of lamellae separated by troughs. Perfect side-to-side packing of C 36 H 74 molecules, the long axis of which stays parallel to Au (110) directions, forms each lamella. Lamella present two different widths (4.8 ± 0.1 and 4.5 ± 0.1 nm) determined by the molecular orientation with respect to troughs. In contrast, the monolayers obtained after UHV deposition at 300 K show poor organization with meandering lamellae and troughs that present strong variations in width. Nevertheless, all the C 38 H 78 molecules stay parallel to the (110) directions of Au(111). Annealing such monolayers at 350 ± 5 K yields a structure that looks like the one observed at the liquid/solid interface. These results show a directional epitaxy relationship perpendicular to the (110) directions of Au(111) in a monolayer of C 36 H 74 and C 38 H 78 molecules. We discuss the origin of the differences observed between the molecule packing at the liquid/solid interface and the one in monolayers built in UHV at 300 K.

Monocrystalline α-Al 2 O 3 (0001) surfaces exhibit various crystallographic structures, depending on the heat treatment they undergo. These different thermally induced surface reconstructions, observed by means of low-energy electron diffraction, correspond to distinct surface compositions, whereas ion bombardment destroys any surface crystallinity but leaves surface stoichiometry unchanged. Whatever the treatment, the band gap is modified, due to changes in the aluminium coordination number and site geometry. These structural modifications were investigated combining X-ray photoelectron and low-energy electron loss spectroscopies.

The initial states of the copper/alumina interface formation by copper vapor deposition are studied on two (0001) α-alumina surfaces, with different crystallographic structures: primitive (1 × 1) and reconstructed (√31 × √31)R ± 9°. The surface phase transition corresponding to the latter surface structure leads to a difference in the growth of copper clusters: on both surfaces, clustering occurs even for the lowest copper coverages, but the size of the clusters is larger on the reconstructed surface than on the primitive one.

By using an atomic force microscope based on a quartz tuning fork sensor, a 3-dimensional description of the interface between liquid hexadecane and a highly oriented pyrolytic graphite surface can be achieved at room temperature. The C16H34 monolayer in contact with the substrate surface exhibits a lamellar structure whereas no observation at the liquid/graphite interface by scanning tunnelling microscopy was reported for this alkane. The second layer shows very weak corrugations corresponding to lamella boundaries. Force/distance curves show at least four oscillations separated by 0.4 nm except for the first period with a 0.38 nm distance that corresponds to the layer closer the substrate. Such a description agrees well with molecular dynamics results obtained on alkane/solid interfaces.

A study performed with a dedicated scanning electron microscope (SEM) on the surface electrical properties of (1 0 0)-oriented yttria-stabilized zirconia (YSZ) single crystals irradiated with 1 MeV electrons is presented. When compared with virgin YSZ, the 1 MeV-irradiated YSZ shows a decrease of the intrinsic total electron emission coefficient σ 0 and an increase of the time constant τ associated with the charging kinetics of the material at room temperature. These measurements performed with the SEM beam at 10 keV indicate that the defects induced by the 1 MeV-electron irradiation generate a positive electric field of the order of 0.5 × 10 6 V/m at a depth of about 1 μm that prevents electrons to escape. When the SEM beam with a 1.1 keV energy is used, a smaller field (∼0.5 × 10 3 V/m) is detected closer to the surface (∼20 nm). The fading of these fields during the thermal annealing in the 400–1000 K temperature range provides information on the nature of defects induced by the 1 MeV-electron irradiation.

Basalts associated with sapphire deposits are widespread in Europe, Africa, Asia and Australia. In Vietnam, blue, green and yellow sapphires are recovered from eluvial and alluvial placers hosted in basaltic fields of the Dak Lak Province. Two distinct basalt suites are recognized in this field: a tholeiitic suite without any xenocrysts and an alkaline suite with mantle and lower crustal xenocrysts. The sapphires are enriched in Fe (0.43 to 1.26 wt.%), with moderate contents of Cr (33–1582 ppm), Ti (35–1080 ppm), Ga (149–308 ppm) and V (28–438 ppm) and they are poor in Zn and Mg. Their O-isotope compositions range from 6.0 to 6.9% and are not in equilibrium with the alkali basalts which have δ18O values between 5.0 and 5.7%. The U-Pb dating of zircons recovered from the basaltic placers provides evidence of two eruptional events: one at ~6.5 Ma followed by another one at ~1 Ma. The petrography of the basalts and the oxygen isotopic composition of the sapphires suggest that the sapphires are xenocrysts and that they crystallized in a deep magma chamber, at the lower continental lithosphere and the upper mantle boundary, in evolved melts issued from the fractionation of alkali basaltic magmas contaminated with lower crustal fluids.

The aim of this study is to present the results of ultrasound-guided needle aspiration in amoebic abscess of the liver in 1289 patients. Out of 1512 patients hospitalized from 1990 to 1995 for an amoebic abscess of the liver, 1289 (83.6%) were treated by this approach. The abscesses of less than 40 mm (8.9%) were treated medically, and those of more than 170 mm (0.6%) were operated on. The abscesses with peritonitis (5.2%) were also operated on. A treatment with metronidazole or dehydroemetin was associated with the surgical treatment or with the aspiration of the abscess. There was no death. A second aspiration was necessary in 24.9% of the patients, and a third one in 9.4%. Three complications were observed, two hemorrhages and one fistula. Nine patients had a recurrent abscess after their discharge from hospital. Four failures were observed in patients with abscesses of more than 170 mm in diameter. Results were considered as good in 1273 patients (98.7%). These results suggest that in amoebic abscess of the liver with a diameter between 40 and 170 mm, aspiration associated with amoebic treatment may be the standard treatment. Smaller abscesses usually recover with medical treatment alone, and greater abscesses need surgical drainage.

Introduction Bien que l'incidence du diabete soit superieure chez les femelles que chez les mâles « non obese diabetic » (NOD), l'influence des estrogenes n'a jamais ete clairement identifiee dans ce modele classique de diabete auto-immun. Compte tenu de leurs effets immunomodulateurs reconnus, notre objectif a ete d'etudier si l'exposition chronique aux estrogenes influence la survenue d'un diabete chez la souris NOD. Materiels et methodes Des souris NOD femelles ont ete traitees de l'âge de 4 a 20 semaines par 17β-estradiol (E2, dose physiologique par voie sous-cutanee). L'influence des estrogenes endogenes a ete etudiee en comparant des souris ovariectomisees a des souris intactes. Resultats Tandis que 80 % des souris controles non traitees developpent un diabete durant la periode de suivi, aucune des souris traitees par E2 n'est affectee (p -/- ). Ecartant l'hypothese d'un role majeur des populations lymphocytaires regulatrices, un effet protecteur complet de l'E2 est retrouve chez des souris NOD deficientes en lymphocytes Natural Killer T (Ja18 -/- ) ou en T regulateurs (CD28 -/- ). Enfin, bien que l'incidence du diabete spontane ne soit pas modifiee, la realisation d'une ovariectomie se traduit par l'acceleration de l'apparition du diabete induit par cyclophosphamide, revelant l'effet protecteur des estrogenes endogenes. Conclusion Les estrogenes previennent l'insulite et l'apparition du diabete chez la souris NOD, permettant d'expliquer que, pour certaines tranches d'âge, l'incidence du diabete type 1 soit soumise a un dimorphisme sexuel. L'activation de la voie de signalisation des estrogenes pourrait donc representer une nouvelle cible pour la prevention du diabete auto-immun.

We describe a method to perform noncontact atomic force microscopy (NC-AFM) in liquid and in air using a quartz crystal tuning fork. The latter, thanks to its increased stability originating from its higher stiffness, compared to cantilevers, enables very low oscillation amplitudes and thus, should yield a very high sensitivity to the force interactions. However, applying conventional NC-AFM technique fails, due to the phase lock loop demodulator becoming unstable as the input signal to noise ratio decreases when lowering the oscillation amplitude. Therefore we have developed so-called zero phase mode atomic force microscopy based on phase modulation. Comparisons with conventional frequency modulation mode using the same mechanical setup demonstrate gains in sensitivity and in scanning rates. High resolution topographic images, as well as simultaneous dissipation images can be recorded using this very convenient and effective technique.