From atomic attrition to mild wear at multi-asperity interfaces:The wear of <i>hard</i> Si₃N₄ repeatedly contacted against <i>soft</i> Si

Wear causes surfaces to be irreversibly damaged, thereby incurring significant economic cost, for instance in the semiconductor industry. Much progress has been made in describing wear at single asperity interfaces between silicon based materials (Si, SiOx, Si3N4), translating the fundamental understanding of wear into wear predictions and control over wear. Yet, predicting and controlling wear at industrially relevant multi-asperity interfaces remains a challenge, especially when considering the wear of the harder material subjected to repeated, nanometric scale displacement. We studied pre-sliding Si3N4-on-Si wear using the atomic force microscopy topography difference method and showed that the harder Si3N4 wears through either atomic attrition or ductile removal enhanced by subsurface damage, depending on the magnitude of the local Si3N4-on-Si contact pressure. Our methods and results bridge fundamental insight into wear based on nanoscale studies to industrial applications.</p

Early Localization of Bronchogenic Carcinoma

The performance of a fluorescence imaging device was compared with conventional white-light bronchoscopy in 100 patients with lung cancer, 46 patients with resected stage I non-small cell lung cancer, 10 patients with head and neck cancer, and 67 volunteers who had smoked at least 1 pack of cigarettes per day for 25 years or more. Using differences in tissue autofluorescence between premalignant, malignant, and normal tissues, fluorescence bronchoscopy was found to detect significantly more areas with moderate/severe dysplasia or carcinoma in situ than conventional white-light bronchoscopy with a similar specificity. Multiple foci of dysplasia or cancer were found in 13–24% of these individuals. Fluorescence bronchoscopy may be an important adjunct to conventional bronchoscopic examination to improve our ability to detect and localize premalignant and early lung cancer lesions

Optimization of Electronic Transport at the Nanoscale through the Formation of Molecular Junctions within Composite Electrodes for Li-battery

National audienc

Modeling lightning-NOx chemistry on a sub-grid scale in a global chemical transport model

For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the nonlinear reactions occurring within high concentrated NO_<i>x</i> plumes from lightning NO_<i>x</i> emissions (LNO_<i>x</i>) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NO_<i>x</i>–O₃ chemical interactions, and the fractions of NO_<i>x</i> conversion into HNO₃ within the plume. Parameter estimates were made using the Dynamical Simple Model of Atmospheric Chemical Complexity (DSMACC) box model, simple plume dispersion simulations, and the 3-D Meso-NH (non-hydrostatic mesoscale atmospheric model). In order to assess the impact of the LNO_<i>x</i> plume approach on the NO_<i>x</i> and O₃ distributions on a large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNO_<i>x</i> parameterization implies an NO_<i>x</i> and O₃ decrease on a large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over central Africa in July) and a relative increase downwind of LNO_<i>x</i> emissions (up to 18 and 2 % for NO_<i>x</i> and O₃, respectively, in July). The calculated variability in NO_<i>x</i> and O₃ mixing ratios around the mean value according to the known uncertainties in the parameter estimates is at a maximum over continental tropical regions with ΔNO_<i>x</i> [−33.1, +29.7] ppt and ΔO₃ [−1.56, +2.16] ppb, in January, and ΔNO_<i>x</i> [−14.3, +21] ppt and ΔO₃ [−1.18, +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows us (i) to reproduce a more realistic lightning NO_<i>x</i> chemistry leading to better NO_<i>x</i> and O₃ distributions on the large scale and (ii) to focus on other improvements to reduce remaining uncertainties from processes related to NO_<i>x</i> chemistry in CTM

PILOT: a balloon-borne experiment to measure the polarized FIR emission of dust grains in the interstellar medium

Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Background, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project which will aim at characterizing one of these foreground sources, the polarization of the dust continuum emission in the diffuse interstellar medium. The PILOT experiment will also constitute a test-bed for using multiplexed bolometer arrays for polarization measurements. We present the results of ground tests obtained just before the first flight of the instrument.Comment: 17 pages, 13 figures. Presented at SPIE, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proc. SPIE volume 915

Calibration and First light of the Diabolo photometer at the Millimetre and Infrared Testa Grigia Observatory

We have designed and built a large-throughput dual channel photometer, Diabolo. This photometer is dedicated to the observation of millimetre continuum diffuse sources, and in particular, of the Sunyaev-Zel'dovich effect and of anisotropies of the 3K background. We describe the optical layout and filtering system of the instrument, which uses two bolometric detectors for simultaneous observations in two frequency channels at 1.2 and 2.1 mm. The bolometers are cooled to a working temperature of 0.1 K provided by a compact dilution cryostat. The photometric and angular responses of the instrument are measured in the laboratory. First astronomical light was detected in March 1995 at the focus of the new Millimetre and Infrared Testa Grigia Observatory (MITO) Telescope. The established sensitivity of the system is of 7 mK_RJ s^1/2$. For a typical map of at least 10 beams, with one hour of integration per beam, one can achieve the rms values of y_SZ ~ 7 10^-5 and the 3K background anisotropy Delta T/T ~ 7 10^-5, in winter conditions. We also report on a novel bolometer AC readout circuit which allows for the first time total power measurements on the sky. This technique alleviates (but does not forbid) the use of chopping with a secondary mirror. This technique and the dilution fridge concept will be used in future scan--modulated space instrument like the ESA Planck mission project.Comment: 10 pages, LaTeX, 12 figures, accepted for publication in Astronomy and Astrophysics Supplement Serie

3,4-Phenylenedioxythiophene (PheDOT): a novel platform for the synthesis of planar substituted pi-donor conjugated systems

3,4-Phenylenedioxythiophene (PheDOT), a benzenic analogue of 3,4-ethylenedioxythiophene (EDOT), has been synthesized using two different routes namely etherification of 2,5-dicarboethoxy-3,4-dihydroxythiophene with halo-aromatics and transetherification of 3,4-dimethoxythiophene with catechols. Quantum calculations and electrochemical measurements show that replacement of the ethylene bridge of EDOT by a phenyl group leads to an increase of the HOMO level and to a stabilization of the cation radical, making electropolymerization of PheDOT more difficult than that of EDOT. The synthesis of several PheDOT derivatives is described together with preliminary results on their electrochemical polymerization and on the properties of the resulting polymers and copolymers