Damage and strain in pseudomorphic vs relaxed GexSi1−x layers on Si(100) generated by Si ion irradiation

We compare both the strain and damage that 100 keV Si irradiation at room temperature introduces in pseudomorphic and relaxed Ge_xSi_1−x films grown on Si(100) substrates. The ion range is such that the Si/Ge_xSi_1−x interface is not significantly damaged. The amount of damage produced in pseudomorphic and relaxed Ge_xSi_1−x layers of similar x for irradiation doses up to 2.5 × 10¹⁴ Si/cm² is the same, which proves that a pre-existing uniform strain does not noticeably affect the irradiation-induced damage. However, the irradiation-induced strain does depend on the pre-existing strain of the samples. Possible interpretations are discussed. On leave from Inst. voor Kern en Stralingsfysika, Catholic University of Leuven, Belgium.     

Structures and morphologies of cast and plastically strained polyamide 6 films as evidenced by confocal Raman microspectroscopy and atomic force microscopy

Both confocal Raman microspectroscopy and atomic force microscopy (AFM) have been undertaken to study the crystalline and the morphological aspects of cast PA 6 films at a sub-microscopic scale. The percentages of the different crystalline structures present within PA 6 cast films, i.e. the monoclinic α, the pseudo-hexagonal β, and the monoclinic γ, have been measured by confocal Raman microspectroscopy. In cast films, the prevailing structure is the β one. AFM has been used to characterize the morphology of the PA 6 films. Simultaneously, the deformed state has been considered as well. Our main interest has been to follow the evolution of the percentage of each crystalline structure as a function of the plastic deformation mechanisms which are responsible of the yielding of PA 6 films: shear banding for temperatures T lower than 160 °C and formation of fibrils for      

Measuring Affective Clarity Indirectly: Individual Differences in Response Latencies of State.

This research investigated a new method to measure momentary affective clarity indirectly, which is based on latencies of responses to state affect items. Three studies revealed that this indirect measure of momentary clarity demonstrated high reliability and stability as well as convergent and predictive validity. The indirect measure was associated with dispositional clarity when the concept of clarity was activated before measuring response latencies (Studies 1 and 2) and was related to self-reports of momentary clarity (Study 3). Furthermore, Study 3 demonstrated that indirectly measured clarity decreased after an affectively complex film. Indirectly, but not directly, measured momentary clarity predicted a more positive affective state at the end of the study. This effect was mediated by affect regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From Powders to Thermally Sprayed Coatings

Since the early stages of thermal spray, it has been recognized that the powder composition, size distribution, shape, mass density, mechanical resistance, components distribution for composite particles play a key role in coating microstructure and thermo mechanical properties. The principal characteristics of particles are strongly linked to the manufacturing process. Coatings also depend on the process used to spray particles and spray parameters. Many papers have been devoted to the relationships existing between coating properties and structures at different scales and manufacturing processes. In many conventional spray conditions resulting in micrometric structures, among the different parameters, good powder flow ability, and dense particles are important features. Thermal plasma treatment, especially by RF plasma, of particles, prepared by different manufacturing processes, allows achieving such properties and it is now developed at an industrial scale. Advantages and drawbacks of this process will be discussed. Another point, which will be approached, is the self-propagating high-temperature synthesis, depending very strongly upon the starting composite particle manufacturing. However, as everybody knows, “small is beautiful” and nano- or finely structured coatings are now extensively studied with spraying of: (i) very complex alloys containing multiple elements which exhibit a glass forming capability when cooled-down, their under-cooling temperature being below the glass transition temperature; (ii) conventional micrometer-sized particles (in the 30-90 μm range) made of agglomerated nanometer-sized particles; (iii) sub-micrometer- or nanometer-sized particles via a suspension in which also, instead of particles, stable sol of nanometer-sized particles can be introduced; and (iv) spray solutions of final material precursor. These different processes using plasma, HVOF or sometimes flame and also cold-gas spray will be discussed together with the production of nanometer-sized particles via the chemical reaction method or by a special type of milling: the cryogenic milling process often referred to as “cryomilling.”     

Reference classes: a tool for benchmarking universities’ research

Based on new comparison principles that take into account both the volume of scientific production and its impact, this paper proposes a method for defining reference classes of universities. Several tools are developed in order to enable university managers to define the value system according to which their university shall be compared to others. We apply this methodology to French universities and illustrate it using the reference classes of the best ranked universities according to several value systems.     

Biodegradability of biomass pyrolysis oils: Comparison to conventional petroleum fuels and alternatives fuels in current use

Concern with environmental issues such as global climate change has stimulated research into the development of more environmentally friendly technologies and energy sources. One critical area of our economy is liquid fuels. Fast pyrolysis of lignocellulosic biomass for liquids production is of particular concern, as it is one of the most interesting ways to produce renewable liquid fuel for transport and heat and power production.The aerobic biodegradability of various pyrolysis oils from different origins and of a EN 590 diesel sample was examined using the Modified Sturm (OECD 301B). The results demonstrate that all fast pyrolysis oils assessed are biodegradable with similar shaped curves with 41–50% biodegradation after 28 days, whereas the diesel sample reached only 24% biodegradation. Since pyrolysis oils achieved biodegradability over 20% these are classified as inherently biodegradable. Modelling of biodegradation processes was successfully performed with a first-order chemical reaction.The biodegradability results obtained for biomass pyrolysis oils are compared to those of conventional and alternative fuels.     

In situ study of the formation of silicide phases in amorphous Co-Si mixed layers

We investigate Co silicide phase formation when extra Si is added within an as deposited 50 nm Co film. The addition of Si is investigated for both the Co/SiO₂ and Co/Si(1 0 0) system. A series of 10 Co-Si mixed films with a Si content varying from 21 to 59 at.% was prepared and investigated during annealing with in situ X-ray diffraction. The oxide system is used as reference system to identify phases that initially crystallize in an amorphous mixture of a given composition. Multiple phases can nucleate, and the temperature of crystallization depends on the Co-Si atomic ratio. Upon heating of the Co(Si)/Si system, the first reaction is a similar crystallization reaction of the Co(Si) mixture. Once the first phase is formed, one has the normal system of a silicide phase in contact with an unlimited amount of Si from the substrate, and the sequential phase formation towards CoSi₂ is established. For deposited layers of composition ranging from 48%Si to 52%Si, the CoSi is the first phase to form and increasing the amount of Si leads to a remarkable improvement of the thermal stability of CoSi on Si(1 0 0). CoSi₂ nucleation was extensively delayed by 150 °C compared to the reaction observed from a pure Co film on Si(1 0 0). Electron backscatter diffraction measurements reveal that in this range, the gradual Si increase systematically leads to bigger CoSi grains (up to 20 μm). This shows that the grain size of the CoSi precursor strongly affects the nucleation of the following CoSi₂ phase. Laser-light scattering measurements suggest that adding more than 42%Si reduces the roughness of the CoSi₂ layer.     

Lateral Magnetically Modulated Multilayers by Combining Ion Implantation and Lithography

The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co‐CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au‐sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature. Conversely, anisotropic magnetoresistance and GMR contributions are distinguished at low temperature (i.e., 10 K) since the O‐implanted areas become exchange coupled. This planar GMR is principally ascribed to the spatial modulation of coercivity in a spring‐magnet‐type configuration, which results in 180° Néel extrinsic domain walls at the Co/Co‐CoO interfaces. The versatility, in terms of pattern size, morphology, and composition adjustment, of this method offers a unique route to fabricate planar systems for, among others, spintronic research and applications.     

A goodness-of-fit test for copula densities

We consider the problem of testing hypotheses on the copula density from a two-dimensional random sample. We test the null hypothesis of a parametric class against a composite nonparametric alternative. Each density under the alternative is separated in the L ₂-norm from any density lying in the null hypothesis. The copula densities under consideration are assumed to belong to a range of Besov balls. According to the minimax approach, the testing problem is solved in an adaptive framework: it leads to a log log  loss term in the minimax rate of testing in comparison with the non-adaptive case. A smoothness-free test statistic that achieves the minimax rate is proposed. The lower bound is also proved.