Three-dimensional (13)C-spectroscopic imaging in the isolated infarcted rat heart

Acquisition weighted (13)C-spectroscopic imaging with three spatial dimensions is demonstrated in the isolated, perfused rat heart. Experiments were performed at 11.75 T with a home-built double resonant (13)C-(1)H probehead. Three-dimensional chemical shift imaging was used to obtain (1)H-decoupled (13)C-spectra in 96-microl voxels in about 58 min. Acquisition weighting significantly reduced signal contamination and improved image quality, with no penalty in sensitivity. As a first application, infarcted hearts were studied during perfusion with [2-(13)C]-sodium acetate. The extent of the incorporation of the (13)C-label into glutamate allows us to distinguish intact and infarcted myocardium. Chemical shift images show a homogeneous glutamate distribution in intact tissue, but a negligible amount in the infarction scar.     

Grid Graphs,Gorenstein Polytopes,and Domino Stackings

We examine domino tilings of rectangular boards, which are in natural bijection with perfect matchings of grid graphs. This leads to the study of their associated perfect matching polytopes, and we present some of their properties, in particular, when these polytopes are Gorenstein. We also introduce the notion of domino stackings and present some results and several open questions. Our techniques use results from graph theory, polyhedral geometry, and enumerative combinatorics.     

3D-snapshot flash NMR imaging of the human heart

SNAPSHOT-FLASH is a recently developed, ultrafast imaging technique, based on conventional FLASH imaging. The application of this new variant to 3D imaging allows the acquisition of a 128 x 128 x 32 data set in 12.5 seconds without triggering, or for cardiac imaging with gating within 32 heartbeats. Compared to standard 3D-FLASH this is 128 times faster, because triggering is only required when the 3D phase-encoding gradient is incremented. The method depicts for the first time fast three-dimensional views of the human heart without motional artifacts. The images are spin-density weighted. Using suitable prepulses any desired T1- or T2-contrast may be achieved. The generation of 3D movies is possible without an increase of the total scan time.     

Synthesis of 5-alkylidene-2,5-dihydropyrrol-2-ones based on cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride

The acid-mediated reaction of amines with γ-alkylidenebutenolides, readily available by cyclization of 1,3-bis(silyloxy)-1,3-butadienes with oxalyl chloride, allows a convenient synthesis of a variety of 5-alkylidene-2,5-dihydropyrrol-2-ones. The configuration of the exocyclic double bond of the products depends on the substitution pattern of the products.     

Fast-switching effect using viscous chiral-nematic materials

We report on chiral-nematic mixtures containing viscous chiral dopants, composed of rigid rod-like chiral molecules, in order to solve the problem of backflow in the middle layers of the liquid crystal cells. During the study, the viscoelastic properties of the liquid crystal compositions have been optimised, as well as the helical twisting power of the chiral compounds, the anchoring energy and the pre-tilt angle of alignment materials, the ratio between the cell gap and the helical pitch (d/P₀). After optimisation, we prepared test cells with low operating voltage – from 1.5 till 5.0 V, fast response time (τ_on + τ_off) – less than 1 ms, wide operating temperature range from ?40°C till +100°C, and good thermal stability. It should be noted that the response time of the new electro-optical mode does not strongly depend on the cell gap, which is in contrast to other known operating modes. We have achieved rather linear than quadratic dependence of the response time when changing the thickness of the cell.