Measuring location, size, distribution, and loading of NiO crystallites in individual SBA-15 pores by electron tomography

By the combination of electron tomography with image segmentation, the properties of 299 NiO crystallites contained in 6 SBA-15 pores were studied. A statistical analysis of the particle size showed that crystallites between 2 and 6 nm were present with a distribution maximum at 3 and 4 nm, for the number-weighted and volume-weighted curves, respectively. Interparticle distances between nearest neighbors were 1-3 nm with very few isolated crystallites. In the examined pores, a local loading twice the applied average of 24 wt % NiO was found. This suggests that a very high local loading combined with a high dispersion is achievable.     

Cardiac-synchronized gadolinium-enhanced MR angiography: preliminary experience for the evaluation of the thoracic aorta

Gadolinium (Gd)-enhanced three-dimensional breath-hold magnetic resonance cardiac-synchronized angiography was performed in 13 patients suspected or known to have thoracic aortic disease. High-quality angiograms of the ascending/descending thoracic aorta and coronary arteries were obtained with this method. MR angiograms were compared with Gd-enhanced angiograms obtained without cardiac synchronization. Synchronized imaging showed significantly better aortic valve leaflet and proximal coronary artery depiction. Synchronization reduced motion artifacts, allowing better visualization of the aortic root and proximal coronary arteries.     

The value of single-shot black-blood MR imaging for mapping of the coronary arteries: a comparison of four different orientations during breath-holding and free breathing

The value of ECG-gated single-shot black-blood MR imaging for rapid visualization of the origin and course of the coronary arteries was investigated. The study population included 28 patients with known or suspected cardiac disease. ECG-gated single-shot black-blood MR acquisitions were acquired in the transverse, coronal, sagittal and LAO orientations, during free breathing and breath-holding. The origin of the left coronary artery was most frequently visualized in the coronal and LAO orientations and the origin of the right coronary artery was most frequently visualized in the LAO orientation. Overall, no significant difference was found for the visualization of the coronary artery segments and the overall image quality among acquisitions during breath-holding and free breathing. ECG-gated single-shot black-blood MR imaging (HASTE) appears to be a time-efficient and robust method for mapping of the entire coronary artery tree, without the need for breath-holding. The LAO orientation provides the most consistent visualization of the origins and major coronary artery segments.     

Nonlocal maximum likelihood estimation method for denoising multiple-coil magnetic resonance images

Effective denoising is vital for proper analysis and accurate quantitative measurements from magnetic resonance (MR) images. Even though many methods were proposed to denoise MR images, only few deal with the estimation of true signal from MR images acquired with phased-array coils. If the magnitude data from phased array coils are reconstructed as the root sum of squares, in the absence of noise correlations and subsampling, the data is assumed to follow a non central-χ distribution. However, when the k-space is subsampled to increase the acquisition speed (as in GRAPPA like methods), noise becomes spatially varying. In this note, we propose a method to denoise multiple-coil acquired MR images. Both the non central-χ distribution and the spatially varying nature of the noise is taken into account in the proposed method. Experiments were conducted on both simulated and real data sets to validate and to demonstrate the effectiveness of the proposed method.     

Untersuchung von Kartoffeln, Gerste und Malz

Ohne Zusammenfassung     

Test-assignment: a quadratic coloring problem

We consider the problem of assigning the test variants of a written exam to the desks of a classroom in such a way that desks that are close-by receive different variants. The problem is a generalization of the Vertex Coloring and we model it as a binary quadratic problem. Exact solution methods based on reformulating the problem in a convex way and applying a general-purpose solver are discussed as well as a Tabu Search algorithm. The methods are extensively evaluated through computational experiments on real-world instances. The problem arises from a real need at the Faculty of Engineering of the University of Bologna where the solution method is now implemented.     

Oxygen binding and activation by the complexes of PY2- and TPA-appended diphenylglycoluril receptors with copper and other metals

The copper(I) complexes of diphenylglycoluril basket receptors and , appended with bis(2-ethylpyridine)amine (PY2) and tris(2-methylpyridine)amine (TPA), respectively, and their dioxygen adducts were studied with low-temperature UV-vis and X-ray absorption spectroscopy (XAS). The copper(I) complex of, [.Cu(I)2] or, forms a micro-eta2:eta2 dioxygen complex, whereas the copper(I) complex of, [.Cu(I)2] or, does not form a well defined dioxygen complex, but is oxidized to Cu(II). Dioxygen is bound irreversibly to and the formed complex is stable over time. The coordination geometries of the above complexes were determined by XAS, which revealed that pyridyl groups and amine N-donors participate in the coordination to Cu(I) ions in the complexes of both receptors. The catalytic activities of various metal complexes of and , that were designed as mimics of dinuclear copper enzymes that can activate dioxygen, were investigated. Phenolic substrates that were expected to undergo aromatic hydroxylation, showed oxidative polymerization without insertion of oxygen. The mechanism of this polymerization turns out to be a radical coupling reaction as was established by experiments with the model substrate 2,4-di-tert-butylphenol. In addition to Cu(II), the Mn(III) complex of and the Fe(II) complex of were tested as oxidation catalysts. Oxidation of catechol was observed for the Cu(II) complex of receptor but the other metal complexes did not lead to oxidation.     

cis-Dihydroxylation and epoxidation of alkenes by [Mn(2)O(RCO(2))(2)(tmtacn)(2)]: tailoring the selectivity of a highly H(2)O(2)-efficient catalyst

The carboxylic acid promoted cis-dihydroxylation and epoxidation of alkenes catalyzed by [MnIV2O3(tmtacn)2]2+ 1 employing H2O2 as oxidant is described. The use of carboxylic acids at cocatalytic levels not only is effective in suppressing the inherent catalase activity of 1, but also enables the tuning of the catalyst's selectivity. Spectroscopic studies and X-ray analysis confirm that the control arises from the in situ formation of carboxylate-bridged dinuclear complexes, for example, 2 {[MnIII2O(CCl3CO2)2(tmtacn)2]2+} and 3 {[MnII2(OH)(CCl3CO2)2(tmtacn)2]+}, during catalysis. For the first time, the possibility to tune, through the carboxylate ligands employed, both the selectivity and activity of dinuclear Mn-based catalysts is demonstrated. To our knowledge, the system 1/2,6-dichlorobenzoic acid (up to 2000 turnover numbers for cis-cyclooctanediol) is the most active Os-free cis-dihydroxylation catalyst reported to date.     

Design of a microfluidic device for comprehensive spatial two‐dimensional liquid chromatography

This study discusses the design aspects for the construction of a microfluidic device for comprehensive spatial two‐dimensional liquid chromatography. In spatial two‐dimensional liquid chromatography each peak is characterized by its coordinates in the plane. After completing the first‐dimension separation all fractions are analyzed in parallel second‐dimension separations. Hence, spatial two‐dimensional liquid chromatography potentially provides much higher peak‐production rates than a coupled column multi‐dimensional liquid chromatography approach in which the second‐dimension analyses are performed sequentially. A chip for spatial two‐dimensional liquid chromatography has been manufactured from cyclic olefin copolymer and features a first‐dimension separation channel and 21 parallel second‐dimension separation channels oriented perpendicularly to the former. Compartmentalization of first‐ and second‐dimension developments by physical barriers allowed for a preferential flow path with a minimal dispersion into the second‐dimension separation channels. To generate a homogenous flow across all the parallel second‐dimension channels, a radially interconnected flow distributor containing two zones of diamond‐shaped pillars was integrated on‐chip. A methacrylate ester based monolithic stationary phase with optimized macroporous structure was created in situ in the confines of the microfluidic chip. In addition, the use of a photomask was explored to localize monolith formation in the parallel second‐dimension channels. Finally, to connect the spatial chip to the liquid chromatography instrument, connector ports were integrated allowing the use of Viper fittings. As an alternative, a chip holder with adjustable clasp locks was designed that allows the clamping force to be adjusted.