A Most Unusual Zeolite Templating: Cage to Cage Connection of One Guest Molecule

An unusual case of a diquaternary ammonium dication, with large bulky end groups built from the tropane moiety and connected by a C4 methylene chain, is found to reside in zeolite SSZ-35 (STF). The structure of the guest/host product is such that the tropane bicylic entities reside in the shallow cavities of the cages of the STF structure and the C4 methylene chain runs through the 10-ring (~5.5 Å) window that connects the cages. This is a most unusual (and energy-intensive) templating of a zeolite structure with the guest molecule spanning two unit cells. The unusual result was found by single crystal studies with the addition of the use of the SQUEEZE program to show a consistent fit for the guest molecule following from measured electron densities in the crystal structure work. These analyses were followed with MAS NMR studies to confirm the integrity of the diquaternary guest molecule in the host sieve. A few comparative diquaternary guest molecules in MFI zeolite are also studied

Calibrations of phase abundance, composition, and particle size distribution for olivine-orthopyroxene mixtures from reflectance spectra

Spectral reflectance measurements of characterized (phase abundance, particle size) mixtures of olivine and orthopyroxene were utilized to define the correlations between spectral and albedo parameters of such assemblages and their mineralogical or textural properties. Thirty-three different spectral parameters falling into three general classes (relative or ratioed, absolute or albedo, and wavelength) were investigated for empirical sensitivity to one or more of the mixture properties. Theoretical considerations and previous experimental observations were utilized to understand their functional relationships. The ratio of areas for the 1- and 2-3µm absorption bands is shown to be a sensitive indicator of the olivine-orthopyroxene abundance and is very nearly independent of particle size and mineral composition. In conjunction with an abundance determination, the wavelength position of the 1-3tm absorption feature can be utilized to determine the molar iron contents of the olivine and orthopyroxene phases. This calibration is insensitive to particle size but will produce systematic deviations if the phases have significantly different iron contents or if more than a few percent of a clinopyroxene component is present. The spectral albedo in the 0.6- to 0.7-µm region is relatively insensitive to phase abundance and can be used to constrain particle size if phase composition has been determinedVarious portions of this work were supported at the University of Hawaii by NASA grant NSG-7312 and by a Sigma Xi Foundation grant to E.A.C. and at Rensselaer Polytechnic Institute by NASA grant NAGW-642. Planetary Geosciences Division, Hawaii Institute of Geophysics, University of Hawaii, publication4 70

Diffusion MRI Tractography of the Developing Human Fetal Heart

Objective: Human myocardium has a complex and anisotropic 3D fiber pattern. It remains unknown, however, when in fetal life this anisotropic pattern develops and whether the human heart is structurally fully mature at birth. We aimed here to use diffusion tensor MRI (DTI) tractography to characterize the evolution of fiber architecture in the developing human fetal heart. Methods: Human fetal hearts (n = 5) between 10–19 weeks of gestation were studied. The heart from a 6-day old neonate and an adult human heart served as controls. The degree of myocardial anisotropy was measured by calculating the fractional anisotropy (FA) index. In addition, fiber tracts were created by numerically integrating the primary eigenvector field in the heart into coherent streamlines. Results: At 10–14 weeks the fetal hearts were highly isotropic and few tracts could be resolved. Between 14–19 weeks the anisotropy seen in the adult heart began to develop. Coherent fiber tracts were well resolved by 19 weeks. The 19-week myocardium, however, remained weakly anisotropic with a low FA and no discernable sheet structure. Conclusions: The human fetal heart remains highly isotropic until 14–19 weeks, at which time cardiomyocytes self-align into coherent tracts. This process lags 2–3 months behind the onset of cardiac contraction, which may be a prerequisite for cardiomyocyte maturation and alignment. No evidence of a connective tissue scaffold guiding this process could be identified by DTI. Maturation of the heart’s sheet structure occurs late in gestation and evolves further after birth

Measures for pathway analysis in brain white matter using diffusion tensor images

In this paper we discuss new measures for connectivity analysis of brain white matter, using MR diffusion tensor imaging. Our approach is based on Riemannian geometry, the viability of which has been demonstrated by various researchers in foregoing work. In the Riemannian framework bundles of axons are represented by geodesies on the manifold. Here we do not discuss methods to compute these geodesies, nor do we rely on the availability of geodesies. Instead we propose local measures which are directly computable from the local DTI data, and which enable us to preselect viable or exclude uninteresting seed points for the potentially time consuming extraction of geodesies. If geodesies are available, our measures can be readily applied to these as well. We consider two types of geodesic measures. One pertains to the connectivity saliency of a geodesic, the second to its stability with respect to local spatial perturbations. For the first type of measure we consider both differential as well as integral measures for characterizing a geodesic's saliency either locally or globally. (In the latter case one needs to be in possession of the geodesic curve, in the former case a single tangent vector suffices.) The second type of measure is intrinsically local, and turns out to be related to a well known tensor in Riemannian geometry.</p

Clinical application of a rapid microbiological test based on capillary zone electrophoresis to assess local skin infection

<p>Abstract</p> <p>Background</p> <p>The basic clinical problem associated with infection treatment is the fact that classic, commonly and routinely used isolation and identification methods are based on long-term processes of a phenotypic analysis of microorganisms. Consequently sometimes, especially in small centres, rapid implementation of antibacterial treatment becomes delayed.</p> <p>The work presents the initial results of rapid microbiological identification based on an original method of capillary zone electrophoresis (CZE). The study involved the analysis of 78 biological samples from post-operative wounds and trophic ulcers.</p> <p>Results</p> <p>The attempt was made to identify individual bacterial species based on characteristic features of electropherograms achieved. Finally, G(+) cocci type bacteria and different G(-) rods were identified with sensitivity of 88.1% and specificity of 100%.</p> <p>Conclusions</p> <p>Based on the clinical trials using an electrophoretic technique in the field of microbiological diagnostics of infected exudate from a post-operative wound it can be concluded that it is a rapid and relatively sensitive method for initial identification of infectious pathogens.</p