3D atom probe tomography of swift heavy ion irradiated multilayers

International audienceNanometer scale layered systems are well suited to investigate atomic transport processes induced by high-energy electronic excitations in materials, through the characterization of the interface transformation. In this study, we used the atom probe technique to determine the distribution of the different elements in an (amorphous-Fe$_2$Tb 5 nm/hcp-Co 3 nm)$_{20}$ multilayer before and after irradiation with Pb ions in the electronic stopping power regime. Atom probe tomography is based on reconstruction of a small volume of a sharp tip evaporated by field effect. It has unique capabilities to characterize internal interfaces and layer chemistry with sub-nanometer scale resolution in three dimensions. Depth composition profiles and 3D element mapping have been determined, evidencing for asymetric interfaces in the as-deposited sample, and very efficient Fe-Co intermixing after irradiation at the fluence $7\times10^{12}$ ion cm$^{-2}$. Estimation of effective atomic diffusion coefficients after irradiation suggests that mixing results from interdiffusion in a molten track across the interface in agreement with the thermal spike model

Impact of differences in the solar irradiance spectrum on surface reflectance retrieval with different radiative transfer codes

Surface reflectance retrieval from imaging spectrometer data as acquired with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has become important for quantitative analysis. In order to calculate surface reflectance from remotely measured radiance, radiative transfer codes such as 5S and MODTRAN2 play an increasing role for removal of scattering and absorption effects of the atmosphere. Accurate knowledge of the exo-atmospheric solar irradiance (E(sub 0)) spectrum at the spectral resolution of the sensor is important for this purpose. The present study investigates the impact of differences in the solar irradiance function, as implemented in a modified version of 5S (M5S), 6S, and MODTRAN2, and as proposed by Green and Gao, on the surface reflectance retrieved from AVIRIS data. Reflectance measured in situ is used as a basis of comparison

AVHRR and VISSR satellite instrument calibration results for both Cirrus and marine stratocumulus IFO periods

Accurate characterizations of some cloud parameters are dependent upon the absolute accuracy of satellite radiance measurements. Visible wavelength measurements from both the AVHRR and VISSR instruments are often used to study cloud characteristics. Both of these instruments were radiometrically calibrated prior to launch, but neither has an onboard device to monitor degradation after launch. During the FIRE/SRB cirrus Intensive Field Operation (IFO), a special effort was made to monitor calibration of these two instruments onboard the NOAA-9 and GOES-6 spacecraft. In addition, several research groups have combined their efforts to assess the long-term performance of both instruments. These results are presented, and a limited comparison is made with the ERBE calibration standard

Development patterns of an isolated oligo-mesophotic carbonate buildup, early Miocene, Yadana field, offshore Myanmar

The development history of an oligo-mesophotic, early Miocene, isolated carbonate system (>160 m in thickness), forming the uppermost part of the Oligo-Miocene Yadana buildup (northern Andaman Sea), has been evidenced from the integration of sedimentological core studies from 4 wells (cumulated core length: 343 m), well correlations, seismic interpretation and analysis of the ecological requirements of the main skeletal components. Three types of carbonate factory operated on the top of the platform, depending on water-depth, turbidity and nutrient level: (1) a scleractinian factory developing under mesophotic conditions during periods of high particulate organic matter supplies, (2) an echinodermal factory occupying dysphotic to aphotic area of the platform coevally with the scleractinian factory, (3) a large benthic foraminiferal-coralline algal factories prevailing under oligo-mesophotic and oligo-mesotrophic conditions. The limited lateral changes in facies between wells, together with the seismic expression of the Yadana buildup, suggest deposition on a flat-topped shelf. Carbonate production and accumulation on the Yadana platform was mainly controlled by light penetration, nutrient content and hydrodynamic conditions. Scleractinian-rich facies resulted from transport of coral pieces derived from mesophotic environments (mounds?) and deposited in deeper, low light, mud-rich environments in which lived abundant communities of suspension feeders such as ophiuroids. Changes in monsoonal intensity, terrestrial runoff from the Irrawaddy River, upwelling currents and internal waves activity during the early Miocene are likely responsible for significant variations in water turbidity and nutrient concentration in the Andaman Sea, thus promoting the development of an oligo-mesophotic, incipiently drowned platform

Passive remote sensing of tropospheric aerosol and atmospheric correction for the aerosol effect

The launch of ADEOS in August 1996 with POLDER, TOMS, and OCTS instruments on board and the future launch of EOS-AM 1 in mid-1998 with MODIS and MISR instruments on board start a new era in remote sensing of aerosol as part of a new remote sensing of the whole Earth system (see a list of the acronyms in the Notation section of the paper). These platforms will be followed by other international platforms with unique aerosol sensing capability, some still in this century (e.g., ENVISAT in 1999). These international spaceborne multispectral, multiangular, and polarization measurements, combined for the first time with international automatic, routine monitoring of aerosol from the ground, are expected to form a quantum leap in our ability to observe the highly variable global aerosol. This new capability is contrasted with present single-channel techniques for AVHRR, Meteosat, and GOES that although poorly calibrated and poorly characterized already generated important aerosol global maps and regional transport assessments. The new data will improve significantly atmospheric corrections for the aerosol effect on remote sensing of the oceans and be used to generate first real-time atmospheric corrections over the land. This special issue summarizes the science behind this change in remote sensing, and the sensitivity studies and applications of the new algorithms to data from present satellite and aircraft instruments. Background information and a summary of a critical discussion that took place in a workshop devoted to this topic is given in this introductory paper. In the discussion it was concluded that the anticipated remote sensing of aerosol simultaneously from several space platforms with different observation strategies, together with continuous validations around the world, is expected to be of significant importance to test remote sensing approaches to characterize the complex and highly variable aerosol field. So far, we have only partial understanding of the information content and accuracy of the radiative transfer inversion of aerosol information from the satellite data, due to lack of sufficient theoretical analysis and applications to proper field data. This limitation will make the anticipated new data even more interesting and challenging. A main concern is the present inadequate ability to sense aerosol absorption, from space or from the ground. Absorption is a critical parameter for climate studies and atmospheric corrections. Over oceans, main concerns are the effects of white caps and dust on the correction scheme. Future improvement in aerosol retrieval and atmospheric corrections will require better climatology of the aerosol properties and understanding of the effects of mixed composition and shape of the particles. The main ingredient missing in the planned remote sensing of aerosol are spaceborne and ground-based lidar observations of the aerosol profiles

Engineering novel complement activity into a pulmonary surfactant protein

Complement neutralizes invading pathogens, stimulates inflammatory and adaptive immune responses, and targets non- or altered-self structures for clearance. In the classical and lectin activation pathways, it is initiated when complexes composed of separate recognition and activation subcomponents bind to a pathogen surface. Despite its apparent complexity, recognition-mediated activation has evolved independently in three separate protein families, C1q, mannose-binding lectins (MBLs), and serum ficolins. Although unrelated, all have bouquet-like architectures and associate with complement-specific serine proteases: MBLs and ficolins with MBL-associated serine protease-2 (MASP-2) and C1q with C1r and C1s. To examine the structural requirements for complement activation, we have created a number of novel recombinant rat MBLs in which the position and orientation of the MASP-binding sites have been changed. We have also engineered MASP binding into a pulmonary surfactant protein (SP-A), which has the same domain structure and architecture as MBL but lacks any intrinsic complement activity. The data reveal that complement activity is remarkably tolerant to changes in the size and orientation of the collagenous stalks of MBL, implying considerable rotational and conformational flexibility in unbound MBL. Furthermore, novel complement activity is introduced concurrently with MASP binding in SP-A but is uncontrolled and occurs even in the absence of a carbohydrate target. Thus, the active rather than the zymogen state is default in lectin·MASP complexes and must be inhibited through additional regions in circulating MBLs until triggered by pathogen recognition

Temporal dominance of sensations of peanuts and peanut products in relation to Hutchings and Lillford’s “breakdown path"

Hutchings and Lillford’s (Journal of Texture Studies, 19, 103-115, 1988) proposed a “breakdown path” whereby particle size reduction occurs through mastication in conjunction with the secretion of saliva to form a swallowable bolus. The swallowing trajectory of whole peanuts, peanut meal and peanut paste were studied with the temporal dominance of sensations technique. The sensations for whole peanuts progressed from hard, to crunchy, to chewy, to soft and ended compacted on teeth. Predictably peanut meal missed out the first two sensations, progressing from chewy, to soft and ending compacted on teeth. However peanut paste, which starts as a soft suspension with relatively little structure appears to thicken and stick to the palate during oral processing. We propose that the “hard to swallow” sensation elicited by peanut paste may be due to water absorption from the saliva as they mix in the mouth

The role of chick Ebf genes in the mediolateral patterning of the somites

This study was conducted to check whether the three chick Early B-cell Factor (Ebf) genes, particularly cEbf1, would be targets for Shh and Bmp signals during somites mediolateral (ML) patterning. Tissue manipulations and gain and loss of function experiments for Shh and Bmp4 were performed and the results revealed that cEbf1 expression was initiated in the cranial presomitic mesoderm by low dose of Bmp4 from the lateral mesoderm and maintained in the ventromedial part of the epithelial somite and the medial sclerotome by Shh from the notochord; while cEbf2/3 expression was induced and maintained by Bmp4 and inhibited by high dose of Shh. To determine whether Ebf1 plays a role in somite patterning, transfection of a dominant-negative construct was carried out; this showed suppression of cPax1 expression in the medial sclerotome and upregulation and medial expansion of cEbf3 and cPax3 expression in sclerotome and dermomyotome, respectively, suggesting that Ebf1 is important for ML patterning. Thus, it is possible that low doses of Bmp4 set up Ebf1 expression which, together with Shh from the notochord, leads to establishment of the medial sclerotome and suppression of lateral identities. These data also conclude that Bmp4 is required in both the medial and lateral domain of the somitic mesoderm to keep the ML identity of the sclerotome through maintenance of cEbf gene expression. These striking findings are novel and give a new insight on the role of Bmp4 on mediolateral patterning of somites