Minor Enantiomer Recycling: Application to Enantioselective Syntheses of Beta Blockers

Continuous recycling of the minor product enantiomer obtained from the acetylcyanation of prochiral aldehydes provided access to highly enantiomerically enriched products. Cyanohydrin derivatives, which under normal conditions are obtained with modest or poor enantiomeric ratios, were formed with high enantiomeric purity by using a reinforcing combination of a chiral Lewis acid catalyst and a biocatalyst. The primarily obtained products were transformed into β‐adrenergic antagonists (S)‐propanolol, (R)‐dichloroisoproterenol, and (R)‐pronethalol by means of a two‐step procedure.     

Images of fluid flow: Art and physics by students

In Spring 2003, a new experimental course on flow visualization was offered to a mixed class of Fine Arts Photography and Engineering students. Course content included fluid flow physics, history of photography with respect to the relationship of science and art, as well as flow visualization and photography techniques. Issues such as “What makes an image art? What makes an image scientific?” were addressed. The class focused on studio/laboratory experiences for mixed teams of students. In Spring 2004 these concepts were distilled into an engineering outreach experience for middle school girls. The spectacular images resulting from these experiments show that flow visualization can be both performed and appreciated by a broad spectrum of people. Thus flow visualization may represent a new bridge between scientists and non-scientists.     

Carotenoids with two chromophores: carotenoid retinoates

In this study, carotenoid retinoates are described for the first time. The preparation was achieved by the azolide method. Various sec carotenols reacted with N-retinoylimidazol in the presence of catalytic amounts of sodium hydride. Mono- and diretinoates of (3R,3'R)-zeaxanthin and its (3S,3'S)-enantiomer, (9Z,9'Z; 3R,3'R)-alloxanthin, (3R,3'R)-7,8,7',8'-tetrahydro-3,3'-dihydroxy-β,β-carotene-8,8'-dione and (3R,6R,3'R,6'R)-ε,ε-carotene-3,3'-diol (lactucaxanthin), as well as monoretinoates of (3R,3'RS,6'R)-3'-methoxy-β,ε-caroten-3-ol, (3R,3'RS,6'R)-3-methoxy-β,ε-caroten-3'-ol, (2R,6'RS)-β,ε-caroten-2-ol, (3R,3'S; meso)-astaxanthin and (2'R)-aleuriaxanthin are reported in this study. Spectroscopic properties ((1)H-NMR mass spectrometry, visible and circular dichroism spectra) are discussed. Studies on other carotenoid derivatives with two chromophores are referred to here.     

Attractive Casimir forces in a closed geometry

We study the Casimir force acting on a conducting piston with arbitrary cross section. We find the exact solution for a rectangular cross section and the first three terms in the asymptotic expansion for small height to width ratio when the cross section is arbitrary. Though weakened by the presence of the walls, the Casimir force turns out to be always attractive. Claims of repulsive Casimir forces for related configurations, like the cube, are invalidated by cutoff dependence.     

A calibration procedure for millimeter-scale stereomicroscopic particle image velocimetry

A stereomicroscopic particle image velocimetry (SμPIV) system has been developed for millimeter scale flows. The SμPIV system is based on an off-the-shelf stereomicroscope, with magnification between 0.69× and 30×, and a field of view between 7.5 × 6 mm and 250 × 200 μm. Custom calibration targets were devised using printed circuit board technology, and applied at a magnification factor of 1.74, with a field of view of 4.75 × 3.8 mm. Measurement errors were assessed by moving a test block with fixed particles. Total system uncertainty in test block displacement transverse to the optical axis was 0.5% of the field of view, and 3% of the depth of field for motion along the optical axis. Approximately 20% of this uncertainty was due to the calibration target quality and test block procedures.     

Discretization of the vorticity field of a planar jet

In data assimilation, information from sensors is used to correct the state variables of a numerical model. This has been used to great advantage by the weather prediction community in the context of direct numerical simulation (DNS) models, but has seen comparatively little use in point-vortex models. This is due in large part to data-processing issues. In order to keep up with the speeds necessary for effective data assimilation, one must extract and discretize the vortex structures from velocity field data in a computationally efficient fashion—i.e., using as few discrete vortices as possible to model the measured flow. This paper describes a new strategy for accomplishing this and evaluates the results using data from a laboratory-scale vortex-dominated planar jet. Large-scale vortex structures are found using a family of variants on traditional vortex extraction methods. By augmenting these methods with simple computational topology techniques, one obtains a new method that finds the boundaries of the coherent structures in a manner that naturally follows the geometry of the flow. This strategy was evaluated in the context of two standard vortex extraction methods, vorticity thresholding and Okubo–Weiss, and tested upon velocity field data from the experimental fluid flow. The large-scale structures found in this manner were then modeled with collections of discrete vortices, and the effects of the grain size of the discretization and the parameters of the discrete vortex model were studied. The results were evaluated by comparing the instantaneous velocity field induced by the discrete vortices to that measured in the jet. These comparisons showed that the two extraction techniques were comparable in terms of sensitivity and error, suggesting that the computationally simpler vorticity thresholding method is more appropriate for applications where speed is an issue, like data assimilation. Comparisons of different discretization strategies showed that modeling each large-scale vortex structure with a single discrete vortex provided the best compromise between mean-squared error and computational effort. These results are of potential interest in any situation where one must balance accuracy and expense while extracting vortices from a snapshot of a flow field; data assimilation is only one example.