Herbert Reingruber

Reconstruction and Characterization of a Polymer-Based Monolithic Stationary phase using Serial Block-Face Scanning Electron Microscopy

Porous, polymer-based materials are increasingly used as stationary phases in separation science and catalysis, yet their morphology remains largely unknown. The main difficulty lies in reconciling their soft matter nature with the demands of microscopic imaging techniques. We analyze the morphology of a hyper-cross-linked poly(styrene-divinylbenzene) monolith in capillary column format from a sample volume of 60.5 × 60.5 × 19.9 μm(3) reconstructed by serial block-face scanning electron microscopy. To obtain a suitable specimen, the polymer skeleton was stained with tetraphenyllead and the void space filled with resin before the whole monolith was resin-embedded after removing the fused-silica capillary. Chord length distribution analysis revealed characteristic lengths of 7.32 and 0.73 μm, corresponding to two distinct macropore types. The macroporosity (77% on average) was found to increase systematically from the wall to the center. Our results provide valuable insights into the formation process of the monolith and its stationary-phase properties.

An ellipsoidal mirror for focusing neutral atomic and molecular beams

Manipulation of atomic and molecular beams is essential to atom optics applications including atom lasers, atom lithography, atom interferometry and neutral atom microscopy. The manipulation of charge-neutral beams of limited polarizability, spin or excitation states remains problematic, but may be overcome by the development of novel diffractive or reflective optical elements. In this paper, we present the first experimental demonstration of atom focusing using an ellipsoidal mirror. The ellipsoidal mirror enables stigmatic off-axis focusing for the first time and we demonstrate focusing of a beam of neutral, ground-state helium atoms down to an approximately circular spot, (26.8±0.5) μm×(31.4±0.8) μm in size. The spot area is two orders of magnitude smaller than previous reflective focusing of atomic beams and is a critical milestone towards the construction of a high-intensity scanning helium microscope.

The 3D pore structure and fluid dynamics simulation of macroporous monoliths: High permeability due to alternating channel width.

Polymethacrylate-based monoliths have excellent flow properties. Flow in the wide channel interconnected with narrow channels is theoretically assumed to account for favorable permeability. Monoliths were cut into 898 slices in 50nm distances and visualized by serial block face scanning electron microscopy (SBEM). A 3D structure was reconstructed and used for the calculation of flow profiles within the monolith and for calculation of pressure drop and permeability by computational fluid dynamics (CFD). The calculated and measured permeabilities showed good agreement. Small channels clearly flowed into wide and wide into small channels in a repetitive manner which supported the hypothesis describing the favorable flow properties of these materials. This alternating property is also reflected in the streamline velocity which fluctuated. These findings were corroborated by artificial monoliths which were composed of regular (interconnected) cells where narrow cells followed wide cells. In the real monolith and the artificial monoliths with interconnected flow channels similar velocity fluctuations could be observed. A two phase flow simulation showed a lateral velocity component, which may contribute to the transport of molecules to the monolith wall. Our study showed that the interconnection of small and wide pores is responsible for the excellent pressure flow properties. This study is also a guide for further design of continuous porous materials to achieve good flow properties.

Poisson's spot with molecules

In the Poisson-spot experiment, waves emanating from a source are blocked by a circular obstacle. Due to their positive on-axis interference an image of the source (the Poisson spot) is observed within the geometrical shadow of the obstacle. In this paper we report the observation of Poissons spot using a beam of neutral deuterium molecules. The wavelength independence and the weak constraints on angular alignment and position of the circular obstacle make Poissons spot a promising candidate for applications ranging from the study of large molecule diffraction to patterning with molecules.

Late onset neuropathy with spontaneous clinical remission in mice lacking the POZ domain of the transcription factor Myc-interacting zinc finger protein 1 (Miz1) in Schwann cells

DOI 10.1074/jbc.A114.605931 Late onset neuropathy with spontaneous clinical remission in mice lacking the POZ domain of the transcription factor Myc-interacting zinc finger protein 1 (Miz1) in Schwann cells. Adrián Sanz-Moreno, David Fuhrmann, Armin Zankel, Herbert Reingruber, Lara Kern, Dies Meijer, Axel Niemann, and Hans-Peter Elsässer PAGE 736: qRT-PCR data quantifying Emr1 expression were missing from Fig. 6. These results are included in panel E of the corrected figure. This correction does not affect the interpretation of the results or the conclusions of this work.

In-situ experiments on soft materials in the environmental SEM — Reliable results or merely damage?

The conventional high vacuum scanning electron microscope is an instrument which is mainly used for the analysis of solid materials. In contrast, the environmental scanning electron microscope (ESEM) is also ideally suited for the operation and control of a great variety of dynamic experiments. Since the type of gas in the specimen chamber, the relative humidity in case of water vapour as gas, the gas pressure and the specimen temperature can be varied over a broad range, an ESEM forms a sort of micro reactor, where the wetting, melting, recrystallization, corrosion … of materials can be investigated.