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Single crystalline magnesium oxide (MgO) nanowires exhibiting a square cross section have been grown on (001)-oriented MgO and Si substrates using the vapor-liquid-solid growth mechanism. While the nanowires grow vertically aligned on MgO, they display random orientations on the silicon substrate. For growth on MgO substrates, the selective placement and density of the nanowires can be controlled by using electron beam lithography for prepatterning the gold catalyst layer. The nanowire samples have been characterized using field-emission scanning electron microscopy and transmission electron microscopy. The described process for selective placement of the nanowires is attractive for their use as templates for coaxial coatings and also for their manipulation for potential device fabrication. [ABSTRACT FROM AUTHOR]

We report on the dynamics of multiphoton excitation and dissociation of NO2 at wavelengths between 395 and 420 nm and intensities between 4 and 10 TW cm-2. The breakup of the molecule is monitored by NO A 2Σ+n′=1,0→X 2Πrn″=0 fluorescence as a function of time delay between the driving field and a probe field which depletes the emission. It is found that generation of n′=0 and 1 NO A 2Σ+ results in different fluorescence modulation patterns due to the intense probe field. The dissociation dynamics are interpreted in terms of nuclear motions over light-induced potentials formed by coupling of NO2 valence and Rydberg states to the applied field. Based on this model, it is argued that the time and intensity dependences of A 2Σ+n′=0→X 2Πrn″=0 fluorescence are consistent with delayed generation of NO A 2Σ+n′=0 via a light-induced bond-hardening brought about by the transient coupling of the dressed à 2B2 and Rydberg 3sσ 2Σg+ states of the parent molecule. The increasingly prompt decay of A 2Σ+n′=1→X 2Πrn″=0 fluorescence with increasing intensity, on the other hand, is consistent with a direct surface crossing between the X 2A1 and 3sσ 2Σg+ dressed states to generate vibrationally excited products. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Three-dimensional atom probe analyses of the interfaces between CoFe and Cu layers has shown that both roughness and chemical intermixing can occur independently. Interfaces formed by the deposition of Cu onto CoFe mimic the roughness present in previously deposited interfaces, but have a very small amount of interfacial mixing. In contrast, interfaces formed by the deposition of CoFe onto Cu are less rough, but more chemically intermixed. The region of chemical intermixing formed when CoFe is deposited onto Cu (0.7-1.0 nm) is approximately two times larger than that when Cu is deposited onto CoFe (0.3-0.5 nm). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Byline: R. Spanjers, A.-F. Rutkowski, R. Martens The paper describes the implementation and acceptance of e-learning in a hospital environment using off-the-shelf technology. Twenty-eight nurses participated in a pilot study that was designed to support an electronic course on advanced electrocardiogram interpretation. The paper presents the procedure and the technologies used to support the e-learning activities. As a follow up of the pilot study, a survey was built and distributed amongst the caregivers of the hospital (N=203). The paper concludes first that the content of the course, a socially structured e-learning environment, as well as the available technologies are important factors to a successful implementation of an e-learning project. Secondly, the paper concludes that the acceptance of such a system to learn is widely supported amongst nurses but seems less convincing to paramedics and physicians. E-learning cannot be perceived as a substitute of a traditional face-to-face education, but when the e-learning environment is socially well structured, it becomes an efficient support to education in the hospital context.

Byline: R. Martens, H. Thielen, T. Sperling, K. Masmeyer In the context of real time (online) decision support systems for nuclear installations, atmospheric dispersion and deposition has to be calculated for a mesoscale area. Typically, the wind field in this area is influenced by topography. Therefore, simple Gaussian type modelling is not appropriate. Initiated and funded by the Bundesamt fur Strahlenschutz, simple (diagnostic mass consistent) flow models were investigated which, with readily available data, can realistically simulate the wind field in a large area. The effect of different initialisation modes of the model has been evaluated. The flow model is one component of a model chain. Other important parts are modules to calculate the atmospheric dispersion, the radiation exposure and counter measures. The initialisation of the flow model has been done based on a) local meteorological observations, typical for a nuclear site, b) prognostic data of the Deutschland-Modell (operational weather forecast model up to the end of 1999) of the Deutscher Wetterdienst, and c) a combination of both datasets a) and b). The present paper deals mainly with the performance of a mass consistent model initialised with the results of an operational weather forecast model.

Byline: H. Thielen, R. Martens, H. Schnadt, K. Ma[sz]meyer Basic concepts, technical applications and details of the updated meteorological pre-processor using SODAR data (MPS) as well as additional meteorological measurements are presented. The pre-processor allows the calculation of boundary-layer parameters, i.e. friction velocity, Monin-Obukhov length and mixing layer height, on the basis of SODAR measurements which serve as input parameters for subsequent dispersion calculations, e.g. within the frame of the DFK model for the calculation of the atmospheric dispersion and radiation exposure related to an accidental release of radioactive material in the near range of a nuclear installation (DFK French-German Commission for Information Interchange on Nuclear Safety). The MPS is an extension to the DFK model which presently only includes the meteorological pre-processor MPT, calculating the boundary layer parameters on the basis of wind-speed data and temperature gradient from tower measurements. The improved DFK model can be implemented within the remote monitoring system of German reactor sites as well as nuclear installations in other countries, provided that either tower data or SODAR data are available as meteorological input.

Atom probe field ion microscopy has been used to analyze a planar-deposited layered structure in plan view. The specimens were prepared with a newly developed method that involves a combination of photolithography and focused ion-beam milling. A multilayer structure consisting of {Ta/CoFe/(Cu/CoFe)[sub 15]/Ru/(CoFe/Ru)[sub 5]/Ru/NiFe} was sputter deposited for use as a test stack. The corresponding thicknesses of these layers were 7/13(3/3)/50/(3/1)/50/150 nm. The nanometer-scale periodicity of the Cu/CoFe stack is readily apparent in transmission electron microscopy images of a field ion specimen fabricated from this material, suggesting that the specimen preparation procedure does not lead to destruction of the multilayer structure. Atom probe analysis of the bulk NiFe layer and the Ru/NiFe interface revealed the distribution of impurity atoms in the film, and these may affect the magnetic properties of the multilayers. Whereas a uniform distribution of C, N and Ar was observed, segregation of O was observed in the NiFe layer within ∼0.25 nm of the interphase interface, with a concentration greater than 20 times that found in the bulk of the NiFe layer. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]