[en] In the scanning tunnelling microscope, the many-body Kondo effect leads to a zero-bias feature of the differential conductance spectra of magnetic adsorbates on surfaces. The intrinsic line shape of this Kondo resonance and its temperature dependence in principle contain valuable information. We use measurements on a molecular Kondo system, all- trans retinoic acid on Au(1 1 1), and model calculations to discuss the role of instrumental broadening. The modulation voltage used for the lock-in detection, noise on the sample voltage, and the temperature of the microscope tip are considered. These sources of broadening affect the apparent line shapes and render difficult a determination of the intrinsic line width, in particular when variable temperatures are involved. (paper)

[en] In this work, calibration and correction of cross-talk in atomic force microscopy (AFM) is demonstrated. Several reasons and effects of this inherent problem on experimental results are discussed. We propose a general procedure that can be used on most AFM systems to compensate for cross-talk on the cantilever bending and twisting signals. The method utilizes two initial experiments on a flat surface to achieve an affine transformation between the measured signals and the actual signals. Using this transformation directly on the voltage signals allows us to remove the detrimental effects of cross-talk on AFM-based force measurement experiments. The achieved transformation matrix can be turned into a simple circuit and applied online, by users who have access to the raw signals in the AFM head. As a case study, a lateral deflection based mechanical characterization test for a poly(methyl methacrylate) microfiber that is suspended on a trench is investigated in terms of the effectiveness of the cross-talk compensation.

No abstract available

[en] In this paper, a neural network modeling of the batch bulk methyl methacrylate polymerization is performed. To obtain conversion, number and weight average molecular weights, three neural networks were built. Each was a multilayer perception with one or two hidden layers. The choice of network topology, i.e. the number of hidden layers and the number of neurons in these layers, was based on achieving a compromise between precision and complexity. Thus, it was intended to have an error as small as possible at the end of back-propagation training phases, while using a network with reduced complexity. The performances of the networks were evaluated by comparing network predictions with training data, validation data (which were not uses for training), and with the results of a mechanistic model. The accurate predictions of neural networks for monomer conversion, number average molecular weight and weight average molecular weight proves that this modeling methodology gives a good representation and generalization of the batch bulk methyl methacrylate polymerization. (author)

[en] A novel methyl methacrylate (MMA) technology developed by Shell Research (Amsterdam) could be simpler and far cheaper than existing MMA manufacturing processes, according to a recent analysis by SRI International (Menlo Park, CA). The Shell palladium-catalyzed process makes MMA from methyl acetylene, avoiding the classic acetone cyanohydrin route. And, says Robert Schwaar, a senior SRI consultant, while availability of methyl acetylene feedstock may limit plant sizes, the Shell technology could make MMA for 44 cts/lb in a 100-million lbs/yr unit. Other commercial and developmental processes, he says, produce MMA at roughly 47 cts-58cts/lb in a 250-million lbs/yr plant. Shell-which is not an MMA producer-has not yet decided the technology's fate. The key question about Shell's process is whether producers can get enough cheap methyl acetylene. The technology calls for separating the methyl acetylene from the mixed C₃ by-product stream

[en] Behavior of the electron produced by two-photonic excitation of an aromatic donor in a poly(methyl methacrylate) solid was studied by the addition of the electron scavengers to the system. According to the Perrin type analysis for the two-photonically ejected electron, the capture radii (R_c) of the scavengers examined were estimated to be from 8 to 40 Angstrom. For the two-photonically ejected electrons, R_c is a capture radius for thermalized electrons. In this case the parent electron donor is not necessarily within this radius. On the other hand, for the fluorescence quenching, the distance between the donor and acceptor is within the static quenching radius (R_q) of the donor. 13 refs., 4 figs., 2 tabs

[en] Different types of healing agents have already been tested on their efficiency for use in self-healing cementitious materials. Generally, commercial healing agents are used while their properties are adjusted for manual crack repair and not for autonomous crack healing. Consequently, the amount of regain in properties due to self-healing of cracks is limited. In this research, a methyl methacrylate (MMA)-based healing agent was developed specifically for use in self-healing cementitious materials. Various parameters were optimized including the viscosity, curing time, strength, etc. After the desired properties were obtained, the healing agent was encapsulated and screened for its self-healing efficiency. The decrease in water permeability due to autonomous crack healing using MMA as a healing agent was similar to the results obtained for manually healed cracks. First results seem promising: however, further research needs to be undertaken in order to obtain an optimal healing agent ready for use in practice

[en] A hybrid molecular mechanics–molecular dynamics (MM–MD) method is proposed to calculate the Young’s modulus of polymers at various temperature. It overcomes the limitation that MD is restricted to extremely high strain rates. A case study based on poly-methyl-methacrylate demonstrates that, contrary to previous MD studies, the method is able to accurately reproduce the effect of temperature on the Young’s modulus in close agreement with experimental data. The method can also predict a more clear transition between the glassy and rubbery states than previous MD studies. (paper)

[en] When exposed to high levels of strain, polymer optical fibre grating sensors recorded in poly(methyl methacrylate) based fibre often exhibit hysteresis in the response of their Bragg wavelength to strain. We demonstrate that the application of pre-tension and annealing of the polymer fibre can reduce this hysteresis when the fibre is suspended freely between two supports, but much better performance is obtained when the sensor is attached directly to a substrate. In this case, the hysteresis can be lessened by more than a factor of 12. (paper)

[en] A research and development program on the radiation curing of wood impregnated with a monomer was initiated in the United States in 1961 by the U.S. Atomic Energy Commission at West Virginia University; this program has continued until today. The USAEC has also sponsored three studies covering different geographical areas of the country, in an attempt to determine the potential of wood-polymer materials. Another effort led to the design of a 200 pound per hour pilot plant for the manufacture of wood-methyl methacrylate materials and projected costs for a 300 pound per hour production plant. And the most recent AEC study involved the evaluation of over 8000 pounds of wood-polymer materials by 68 manufacturers of wood products; the wood-polymer materials utilizing 41 species of wood were produced for the AEC by Lockheed-Georgia Company, Dawsonville, Georgia. In 1965, studies on the thermal-catalytic production of wood polymers were begun at the College of Forestry, Syracuse University, Syracuse, New York