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Why One Disk Is Better Than Two
Nov. 25, 2013

Why One Disk Is Better Than Two

A novel optical concept for a spinning disk confocal microscope is presented, which warrants maximal optical quality, speed and usability. It employs a single disk only instead of two, and it uses micromirrors instead of microlenses, thus minimizing chromatic aberrations and yielding an uncompromised performance over the full visible range from 405 - 700 nm. Careful optimization of coupling optics result in flat and homogenous illumination free of speckle artifacts, and the full optical performance is maintained over the full field of view. 
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Trouble-Free 2-Photon Microscopy
Nov. 20, 2013

Trouble-Free 2-Photon Microscopy

Two-photon (2P) absorption spectra of fluorescent dyes are broader than single-photon ones. Simultaneous 2P excitation of several dyes with a single wavelength (WL) is feasible and can be seen as an advantage. We used femtosecond (fs) pulsed fixed-WL infrared lasers with center WLs at 780 nm and 1040 nm, respectively, for Two-Photon Microscopy (2PM) in biologically relevant samples. The 1040 nm laser proved to be very efficient in exciting fluorescence from YFP and red fluorescent dyes, but also in generating second harmonic generation (SHG) from muscle tissue and collagen. We demonstrate that economical, small-footprint fixed-WL lasers can present adequate replacement for commonly used Ti:Sapphire (Ti:Sa) lasers, the size, price and handling of which causes considerable pain for microscope users.
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Bioluminescence Microscopy
Nov. 12, 2013

Bioluminescence Microscopy

In contrast to fluorescence methods, bioluminescence microscopy does not need excitation by light. As photon emission results from a chemical reaction, results are highly specific and quantifiable. Until recently bioluminescence microscopy was difficult to approach as a result of rather dim signal intensities. Due to better probes and especially thanks to better and more specific instrumentation this technique has now become much more accessible and can in many situations outperform fluorescent approaches. more
Precipitation in an Al-Mg-Si-Ge-Cu Alloy
Oct. 29, 2013

Precipitation in an Al-Mg-Si-Ge-Cu Alloy

Al-Mg-Si(-Cu) alloys are age-hardenable alloys, an industrially important group of materials that get their strength from the precipitation of needle-shaped metastable phases during heat treatment. In this work, precipitates in an Al-Mg-Si-Ge-Cu alloy are studied by HAADF STEM. The images reveal that the precipitates, when viewed along the needle direction, have no repeating unit cell, but instead consist of single structural units that appear in different orientations.
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Messengers from Space
Oct. 10, 2013

Messengers from Space

The macro- and microstructure of iron meteorites provide valuable insights into both the inner structure of our planet and the history of our solar system. High speed collision events in the asteroid belt send the meteorites careening toward Earth. The collisions produce unique deformation microstructures. With cooling rates on the scale of a few degrees per million years, iron meteorites can consist of crystal sizes on the order of meters prior to the collision events. These extremely slow cooling rates result in phase transformations occurring at conditions near thermodynamic equilibrium. Preserving meteorite fragments is important for future studies of phase transformations, material behavior at high strain rates, and the origin of the universe.
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In Situ Straining Analysis with ACOM-TEM
Oct. 05, 2013

In Situ Straining Analysis with ACOM-TEM

The combination of ACOM-TEM with in situ straining inside a TEM enables direct imaging of the local crystal orientation at the nanoscale during straining of nanocrystalline metals and thus various deformation processes such as grain growth, twinning/detwinning and grain rotation can be distinguished in real space. A quantitative analysis of the crystal orientation changes observed by this new approach was used to study the deformation processes in nanocrystalline gold [1].
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Exploring Teeth by Analytical (S)TEM
Sep. 23, 2013

Exploring Teeth by Analytical (S)TEM

Mineralized human dental tissues were studied by advanced analytical transmission electron microscopy (TEM) techniques. The Ca/P and Mg/P at % ratios were determined employing energy dispersive X-ray spectroscopy (EDX) measurements. Significantly lower Ca/P and higher Mg/P at % ratios were measured in peritubular dentine compared to intertubular dentine, suggesting the incorporation of Mg in the hydroxylapatite lattice by substituting Ca. Improvement of TEM sample preparation is demonstrated. more
A New Type of Laser Diode
Sep. 06, 2013

A New Type of Laser Diode

Exciton-polaritons are bosonic quasi particles which mix the properties of excitons and photons [1]. They can undergo a dynamic phase transition, sharing many similarities with Bose-Einstein condensation of ultra-cold atoms. However, due to the light effective mass of polaritons, this transition can take place at much higher temperatures, even up to 300 K in large bandgap semiconductors [2]. When this transition occurs, a macroscopic number of particles populate a common energy state. The photons, which spontaneously leak out of the microcavity, adopt the monochromatic and coherent nature of the polaritons. To date, the effects of polariton condensation and lasing have only been observed in various optically pumped systems [2-5], whereas the clear demonstration of polariton lasing under electrical pumping, which represents a crucial step towards most applications, has been obsolete. more
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