3D measurement of micromechanical devices vibration mode shapes with a stroboscopic interferometric microscope

Microscopic interferometry is a powerful technique for the static and dynamic characterization of micromechanical devices. In this paper we emphasize its capabilities for 3D vibration mode shapes profiling of Al cantilever microbeams and Cr micromachined membranes. It is demonstrated that time-resolved measurements up to 800 kHz can be performed with a lateral resolution in the micrometer range and a vibration amplitude detection limit of 3–5 nm. In addition, with reduced image sizes (256×256), quasi-real time (150–500 ms) visualization of the vibration mode 3D profiles becomes possible. These performances were obtained by using stroboscopic illumination with an array of superluminescent LED and an optimized automatic fast Fourier transform phase demodulation of the interferograms. The results are compared with theoretical shapes of the vibration modes and with point measurements of the vibration spectra.     

Development of a practical solid-phase synthesis approach to 1,3,5-triazepan-2,6-diones

1,3,5-Triazepan-2,6-diones are a class of conformationally restricted heterocycles derived from dipeptides. With the aim to develop a general and practical method useful for library production, three polymer-assisted syntheses, all based on a catch and release approach, have been evaluated and compared. The method involving a Hofmann rearrangement of N-Boc dipeptide carboxamides and subsequent trapping of the isocyanate on polymer-supported N-hydroxysuccinimide (PS-HOSu) was found to be the most reliable and versatile, allowing rapid access to the 1,3,5-triazepan-2,6-dione skeleton.     

Evaluation of quantitative structure-activity predictions. Comparison of the predictive power of an artificial intelligence system with human experts

In this paper, we present three new mathematical techniques for evaluating the predictive skills of structure-activity experts. The question addressed in this paper is how to evaluate the predictive ability of structure-activity experts in identifying the most active compounds of a set of drug candidates. The three proposed mathematical techniques are based on the Phi-square Distance, the Rank Comparison, and the Shuffle method, respectively. They have been used to evaluate the performance of a new computer system and three human experts in predicting the antibacterial potencies of a series of chemical compounds in five different biological tests. The expert system, an artificial intelligence structure-activity program called MULTICASE, performed significantly better than one of the human experts and somewhat better than the other two.On leave from the Department of General and Analytical Chemistry, Technical University of Budapest, Szt. Gellert ter 4, 1111 Budapest, Hungary.     

Silica-supported l-proline organocatalysts for asymmetric aldolisation

New heterogenised silica-based organocatalysts have been prepared via the sol–gel process from two silylated derivatives of l-proline, featuring either a carbamate or an ether linker. Co-gelification with variable amounts of TEOS was performed with and without porogen to yield high surface area solids. These materials were evaluated as heterogeneous phase organocatalysts for the asymmetric aldol reaction of p-nitrobenzaldehyde with acetone.     

Regiocontrolled fluorination of 2-hydroxyalkyl dihydropyrans and carbonyl derivatives

Reaction of polysubstituted 2-hydroxyalkyldihydropyrans with DAST led regiospecifically to fluorination at the exocyclic position, except for primary alcohols. Difluorination of carbonylated analogues with deoxo-fluor™ occurred also regioselectively. The unexpected stability and synthetic potential of these new allylic fluorides are discussed.     

Disjunctive cuts for continuous linear bilevel programming

This work shows how disjunctive cuts can be generated for a bilevel linear programming problem (BLP) with continuous variables. First, a brief summary on disjunctive programming and bilevel programming is presented. Then duality theory is used to reformulate BLP as a disjunctive program and, from there, disjunctive programming results are applied to derive valid cuts. These cuts tighten the domain of the linear relaxation of BLP. An example is given to illustrate this idea, and a discussion follows on how these cuts may be incorporated in an algorithm for solving BLP.     

Magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches

The results of an investigation of the magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches are reported. Oscillations of the equatorial Kerr effect as a function of the copper wedge thickness are observed. The period of these oscillations is found to be of the order of 5–6 Å. The experimentally observed oscillations of the equatorial Kerr effect are attributed to a quantum size effect. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 33–36 (10 January 1998)     

A note on the first nonzero eigenvalue of the laplacian acting on P-forms

The first author was supported by the Swiss National Sciences Foundation and the second author was partially supported by contrat CEE GADGET.SC1-0105-C.