Diastereoselective multicomponent synthesis of dihydropyridones with an isocyanide functionality

[Structure: see text] In a search for new multicomponent strategies leading to valuable small heterocycles, a new highly diastereoselective four-component reaction (4CR) was found in which a phosphonate, nitriles, aldehydes, and isocyanoacetates combine to afford functionalized 3-isocyano-3,4-dihydro-2-pyridones. In this strategy, initially a 1-azadiene is generated, which is trapped in the same pot by an isocyanoacetate as the fourth component. Multicomponent reactions (MCRs) that lead to heterocycles containing isocyano substituents are unprecedented and offer many possibilities for further differentiation.     

Optical parametric oscillator based off-axis integrated cavity output spectroscopy for rapid chemical sensing

An optical parametric oscillator (OPO), pumped by a fiber-amplified diode laser, is combined with off-axis integrated cavity output spectroscopy (OA-ICOS). The cw OPO (power 1.2 W, tunability 3-4 μm, 5 cm(-1) mode-hop-free tuning) has a tuning speed of 100 THz/s, which is ideal for rapid and sensitive trace gas detection. Combined with OA-ICOS, a detection limit of 50 parts per trillion by volume (1×10(12)) of ethane (C(2)H(6)) in nitrogen was obtained in 0.25s at 2997 cm(-1), corresponding to a noise equivalent absorption sensitivity of 4.8×10(-11) cm(-1) Hz(-1/2). The system demonstrates real-time measurements of methane and water in exhaled human breath.     

Algorithms for the universal and a priori TSP

We present two simple results for generalizations of the traveling salesman problem (TSP): for the universal TSP, we show that one can compute a tour that is universally optimal whenever the input is a tree metric. A (randomized) O(logn)-approximation algorithm for the a priori TSP follows as a corollary.     

The Search for Pseudo Orthogonal Latin Squares of Order Six

We report on the completecomputer search for a strongly regular graph with parameters(36,15,6,6) and chromatic number six. The resultis that no such graph exists.     

Nonlinear Kernels and Their Resolvents

In [1], Dellacherie showed that also nonlinear kernels can have a resolvent associated with them. In this text, we will generalise some of his results to the case where the complete maximum principle does not hold.     

Direct writing of microtunnels using proton beam micromachining

The production of high aspect ratio microstructures is a potential growth area. The combination of deep X-ray lithography with electroforming and micromolding (i.e. LIGA) is one of the main techniques used to produce 3D microstructures. The new technique of proton micromachining employs focused MeV protons in a direct write process which is complementary to LIGA. During ion exposure of positive photoresist like PMMA, scission of molecular chains occurs. These degraded polymer chains are removed by the developer. The aim of this paper is to investigate the capabilities of proton micromachining as a lithographic technique. We show the realization of sub-surface channels, or microtunnels, which have been fabricated in only one exposure and without cutting or resurfacing the material. Using our Van-de-Graaff accelerator, the resist (PMMA) has been exposed with high-energy protons (2.5 MeV). The range of charged particles in matter is well-defined and depends on the energy. Therefore, it is possible to obtain a dose which is sufficient to develop the bottom part of the ion paths but not the top part. Thus, by selecting the energy and the exposure time, a big variety of microtunnels can be realized.