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Malik S.,Karlsruhe Institute of Technology | Vijayaraghavan A.,Karlsruhe Institute of Technology | Vijayaraghavan A.,Massachusetts Institute of Technology | Erni R.,Electronic Microscopy Center | And 4 more authors.
Nanoscale | Year: 2010

A simple method of fabricating pristine few-layer and single-layer graphene which could be used for production on a gram scale is described. © The Royal Society of Chemistry 2010.

Erni R.,Electronic Microscopy Center | Erni R.,Lawrence Berkeley National Laboratory | Rossell M.D.,Lawrence Berkeley National Laboratory | Rossell M.D.,ETH Zurich | Nakashima P.N.H.,Monash University
Ultramicroscopy | Year: 2010

Atomic-resolution transmission electron microscopy has largely benefited from the implementation of aberration correctors in the imaging part of the microscope. Though the dominant geometrical axial aberrations can in principle be corrected or suitably adjusted, the impact of higher-order aberrations, which are mainly due to the implementation of non-round electron optical elements, on the imaging process remains unclear. Based on a semi-empirical criterion, we analyze the impact of residual aperture aberrations on the quality of exit-plane waves that are retrieved from through-focal series recorded using an aberration-corrected and monochromated instrument which was operated at 300 kV and enabled for an information transfer of ∼0.05 nm. We show that the impact of some of the higher-order aberrations in retrieved exit-plane waves can be balanced by a suitable adjustment of symmetry equivalent lower-order aberrations. We find that proper compensation and correction of 1st and 2nd order aberrations is critical, and that the required accuracy is difficult to achieve. This results in an apparent insensitivity towards residual higher-order aberrations. We also investigate the influence of the detector characteristics on the image contrast. We find that correction for the modulation transfer function results in a contrast gain of up to 40%. © 2009 Elsevier B.V. All rights reserved.

Dwyer C.,Monash University | Erni R.,Electronic Microscopy Center | Etheridge J.,Monash University
Ultramicroscopy | Year: 2010

We review the manner in which lens aberrations, partial spatial coherence, and partial temporal coherence affect the formation of a sub-̊A. electron probe in an aberration-corrected transmission electron microscope. Simulations are used to examine the effect of each of these factors on a STEM image. It is found that the effects of partial spatial coherence (resulting from finite effective source size) are dominant, while the effects of residual lens aberrations and partial temporal coherence produce only subtle changes from an ideal image. We also review the way in which partial spatial and temporal coherence effects are manifest in a Ronchigram. Finally, we provide a demonstration of the Ronchigram method for measuring the effective source distribution in a probe aberration-corrected 300. kV field-emission gun transmission electron microscope. © 2010 Elsevier B.V.

PubMed | University of Texas at Austin, Empa - Swiss Federal Laboratories for Materials Science and Technology, ETH Zurich, IBM and Electronic Microscopy Center
Type: | Journal: Nanotechnology | Year: 2016

Significant progress has been made in integrating novel materials into silicon photonic structures in order to extend the functionality of photonic circuits. One of these promising optical materials is BaTiO3 or barium titanate (BTO) that exhibits a very large Pockels coefficient as required for high-speed light modulators. However, all previous demonstrations show a noticable reduction of the Pockels effect in BTO thin films deposited on silicon substrates compared to BTO bulk crystals. Here, we report on the strong dependence of the Pockels effect in BTO thin films on their microstructure, and provide guidelines on how to engineer thin films with strong electro-optical response. We employ several deposition methods such as molecular beam epitaxy and chemical vapor deposition to realize BTO thin films with different morphology and crystalline structure. While a linear electro-optic response is present even in porous, polycrystalline BTO thin films with an effective Pockels coefficient reff = 6 pm/V, it is maximized for dense, tetragonal, epitaxial BTO films (reff= 140 pm/V). By identifying the key structural predictors of electro-optic response in BTO/Si, we provide a roadmap to fully exploit the linear electro-optic effect in novel hybrid oxide/semiconductor nanophotonic devices.

Brockmann T.,University Medicine Berlin | Brockmann C.,University Medicine Berlin | Nietzsche S.,Electronic Microscopy Center | Bertelmann E.,University Medicine Berlin | And 3 more authors.
Journal of Cataract and Refractive Surgery | Year: 2013

Purpose To evaluate commercially available 1- and 3-piece intraocular lenses (IOLs) with scanning electron microscopy (SEM). Setting Department of Ophthalmology and Electron Microscopy Center, University Hospital Jena, Jena, Germany. Design Experimental study. Methods Seven +23.0 diopter IOLs of different design and material and from different manufacturers were chosen for a detailed assessment. Scanning electron microscopy was used at standardized magnifications to assess typical IOL characteristics. The particular focus was the optic edge, the optic surface, the haptic-optic junction, and the haptic. Results All square-edged IOLs had a curvature radius of less than 10 μm, while the mean optic edge thickness ranged between 216 μm and 382 μm. A 360-degree square-edged boundary was present in all 3-piece IOLs and in a single 1-piece model. Relevant production remnants on the optic edge were observed in 1 case. Regarding the haptic, 3-piece IOLs had uniformly shaped fibers with a mean thickness of 177 μm ± 51 (SD) (range 116 to 220 μm). Chemical adhesives were used to attach the haptic in 1 case, where alterations of the IOL material were observed. In another case, the haptic fiber was press-fitted into the optic, which resulted in bulging of the optic profile. Inspection of surface characteristics showed wavelike patterns in 2 IOLs. Conclusions Taking clinical relevance into account, all IOLs were of high manufacturing quality. Certain attention was paid in creating a sharp optic edge. Surface irregularities of 2 IOLs were attributed to the manufacturing technique. Methods for implementing the haptic-optic junction were diverse. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned. © 2013 ASCRS and ESCRS.

Ardelean M.,Vasile Goldis Western University of Arad | Cachita D.M.,Vasile Goldis Western University of Arad | Ardelean A.,Vasile Goldis Western University of Arad | Craciun C.,Electronic Microscopy Center
Annals of the Romanian Society for Cell Biology | Year: 2014

The factors determining anthocyanin (vegetal, natural dyes) synthesis in plant cells are still unclear. At Sedum telephium ssp. maximum L. plants grown in natural conditions, the raspberry-red anthocyanin accumulation occurs in the stem epidermis and in the aging leaves especially in areas exposed directly to sunlight. However according to our observation (microscopy) we determined that only a small part of the epidermal cells and less frequently the cells of caulinar bark or foliar mesophill have this dye in the vacuolar content. The ability of some cells to color in red their vacuolar content while the cells in their immediate vicinity are colorless is unexplained in literature. Thus Sedum telephium ssp. maximum L. cells in immediate proximity of stomata have anthocyaninis in their vacuoles whereas stomata cells are colorless. In a basic pH the color of vacuolar anthocyanins change from red in blue and vice versa.Our research showed that different stress factors particularly the direct incidence of solar radiation produces in time this phenomenon. This occurs both in the stem epidermis as well as in the leaves of this species and it is possible to fulfill a protecting or antioxidant function. © Annals of R. S. C. B.

Ardelean M.,Vasile Goldis Western University of Arad | Cachita D.M.,Vasile Goldis Western University of Arad | Mihali C.V.,Vasile Goldis Western University of Arad | Craciun C.,Electronic Microscopy Center
Annals of the Romanian Society for Cell Biology | Year: 2014

We have innitiated vitrocultures of Sedum telephium ssp. maximum L. from embryos of seeds germinated „in vitro” on a agarized Murashige-Skoog (1962) medium with added auxin (NAA or IBA) and cytokinin (KIN or BA), 0,5mg/l of each were added in case of seeds and 1,5 mg/l in case of the subcultures made from propagules taken from vitrocultures innitiated from embryos. This allowed us to distinguish at the leaflets and stalks epidermis level that amomg stomata and their neighbouring cells, are randomly distributed cells that had raspberry – red colored vacuoles, possibly due to anthocyanin accumulation.The existence of such formations (anthocyanins) has also been observed using optical or electron microscopy.In the foliar mesophyle are less anthocyanin containing cells with the exception of hyperhydrated tissues in which the presence of such cells was frequent and often the vacuolar content was transformed in a black compact mass. We have associated anthocyanin synthesis with the stress conditions because at the young plants in nature this phenomenon is present. © Annals of R. S. C. B.

Reis L.A.,UNIFESP EPM | Borges F.T.,UNIFESP EPM | Simoes M.J.,UNIFESP EPM | Borges A.A.,Electronic Microscopy Center | And 2 more authors.
PLoS ONE | Year: 2012

This study evaluated the effects of bone marrow-derived mesenchymal stem cells (BMSCs) or their conditioned medium (CM) on the repair and prevention of Acute Kidney Injury (AKI) induced by gentamicin (G). Animals received daily injections of G up to 20 days. On the 10th day, injections of BMSCs, CM, CM+trypsin, CM+RNase or exosome-like microvesicles extracted from the CM were administered. In the prevention groups, the animals received the BMSCs 24 h before or on the 5th day of G treatment. Creatinine (Cr), urea (U), FENa and cytokines were quantified. The kidneys were evaluated using hematoxylin/eosin staining and immunohystochemistry. The levels of Cr, U and FENa increased during all the periods of G treatment. The BMSC transplantation, its CM or exosome injections inhibited the increase in Cr, U, FENa, necrosis, apoptosis and also increased cell proliferation. The pro-inflammatory cytokines decreased while the anti-inflammatory cytokines increased compared to G. When the CM or its exosomes were incubated with RNase (but not trypsin), these effects were blunted. The Y chromosome was not observed in the 24-h prevention group, but it persisted in the kidney for all of the periods analyzed, suggesting that the injury is necessary for the docking and maintenance of BMSCs in the kidney. In conclusion, the BMSCs and CM minimized the G-induced renal damage through paracrine effects, most likely through the RNA carried by the exosome-like microvesicles. The use of the CM from BMSCs can be a potential therapeutic tool for this type of nephrotoxicity, allowing for the avoidance of cell transplantations. © 2012 Reis et al.

Kuc J.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Zhang Y.,Electronic Microscopy Center | Erni R.,Electronic Microscopy Center | Yoon S.,Empa - Swiss Federal Laboratories for Materials Science and Technology | And 3 more authors.
Physica Status Solidi - Rapid Research Letters | Year: 2015

The self-regenerative property of LaCo1-x -yPdx Zny O3±δ and LaFe1-x -yPdx Zny O3±δ solid solutions with monometallic Pd or bimetallic Pd/Zn substituents for Co or Fe is studied under a redox cycle by high angular annular dark-field scanning transmission electron microscopy (STEM-HAADF) and energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). These results reveal that the composition of perovskites determines the self-regenerative property that occurs largely in LaCo1-x -yPdx Zny O3±δ but is limited greatly in LaFe1-x -yPdx Zny O3±δ. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lewin E.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Parlinska-Wojtan M.,Electronic Microscopy Center | Parlinska-Wojtan M.,University of Rzeszow | Patscheider J.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Journal of Materials Chemistry | Year: 2012

Coatings of the Al-Ge-N system were synthesized using reactive DC magnetron sputtering and characterized to determine their structure and properties, as well as their potential usage as hard optical coatings. Coatings were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and both scanning and transmission electron microscopy. Besides the binary reference samples (AlN and Ge 3N 4), ternary samples with Ge contents from 5 to 28 at% were produced and found to be either a solid solution phase of nanocrystalline (Al 1-xGe x)N, or nanocomposites of this phase and an amorphous Ge 3N 4-y phase. The grain size of the (Al 1-xGe x)N phase decreases with increasing Ge content, from about 30 to about 15 nm. The (Al 1-xGe x)N phase was found to exhibit two different textures: at low Ge content a (001) preferred orientation was observed, while at higher Ge content the (110) orientation became dominant. The Ge 3N 4-y phase was found to be highly susceptible to sputter damage during sputter-cleaning prior to XPS analysis. Ternary coatings were found to have a hardness between 18 and 24 GPa. The optical absorption edge was found to be tunable through variation of Ge content, and ranged from 260 to 350 nm, corresponding to an optical bandgap (E 04) of 4.7 to 3.5 eV. Also the index of refraction (n) shows a slight dependence of Ge content, increasing from about 2.0 to 2.3. Thus these coatings have a potential use as protective coatings for optical components operating in the visual or near-IR range, and possibly as UV-blocking filters with a tunable absorption edge. © The Royal Society of Chemistry 2012.

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