HRTEM of 1DSnTe@SWNT nanocomposite located on thin layers of graphite.

The method for imaging of highly sensitive nanostructures unstable under electron beam irradiation is introduced. To reduce charge and thermally generated beam damage, highly conductive multilayered graphene or thin graphite layers were used as supports for nanostructures. Well-defined crystalline structure of graphite layers enables image reconstruction by Fourier filtering and allows maintaining high quality of images. The approach was tested for imaging of highly sensitive quasi one-dimensional SnTe nanocrystals hosted inside single-walled carbon nanotubes. Relying on the filtered images and the image simulation, the structure of one-dimensional SnTe was established as a chain of fcc NaCl type unit cells, connected by the [001] edges with <110> direction coinciding with nanotube axis.

Using a monochromator to improve the resolution in TEM to below 0.5 Å. Part II: application to focal series reconstruction.

We apply monochromated illumination to improve the information transfer in focal series reconstruction to 0.5 Å at 300 kV. Contrary to single images, which can be taken arbitrarily close to Gaussian focus in a C(S)-corrected microscope, images in a focal series are taken at a certain defocus. This defocus poses limits on the spatial coherence of the illumination, and through this, limits on the brightness of the monochromated illumination. We derive an estimate for the minimum spatial coherence and the minimal brightness needed for a certain resolution at a certain defocus and apply this estimate to our focal series experiments. We find that the 0.5 Å information transfer would have been difficult and probably impossible to obtain without the exceptionally high brightness of the monochromated illumination.

The structure of nanocomposite 1D cationic conductor crystal@SWNT.

Nanocomposites consisting of one-dimensional (1D) crystals of the cationic conductors CuI, CuBr and AgBr inside single-walled carbon nanotubes, mainly (n, 0), were obtained using the capillary technique. 1D crystal structure models were proposed based on the high resolution transmission electron microscopy performed on a FEI Titan 80-300 at 80 kV with aberration correction. According to the models and image simulations there are two modifications of 1D crystal: hexagonal close-packed bromine (iodine) anion sublattice (growth direction <001>) and 1D crystal cubic structure (growth direction <112>) compressed transversely to the nanotube (D(m) ∼1.33 nm) axis. Tentatively this kind of 1D crystal can be considered as monoclinic. One modification of the anion sublattice reversibly transforms into the other inside the nanotube, probably initiated by electron beam heating. As demonstrated by micrographs, copper or silver cations can occupy octahedral positions or are statistically distributed across two tetrahedral positions. A 1DAgBr@SWNT (18, 0; 19, 0) pseudoperiodic 'lattice distortion' is revealed resulting from convolution of the nanotube wall function image with 1D cubic crystal function image.

Using a monochromator to improve the resolution in TEM to below 0.5Å. Part I: Creating highly coherent monochromated illumination.

Chromatic aberration limits the resolution in spherical-aberration corrected Transmission Electron Microscopy to approximately 0.7Å at 300 kV. The energy spread in the beam is the main contribution to the chromatic aberration. This spread can be reduced with a monochromator. Another limitation to the resolution in TEM can be the finite brightness of the source and the consequent partial spatial coherence of the illumination. This limitation becomes important when spherical aberration and/or defocus are present such as in uncorrected TEM or in focal-series reconstruction in TEM. We used a monochromator optimized for minimum brightness loss and a prototype 'high-brightness' gun, and obtained brightness after monochromation comparable to that of the standard Schottky FEG before monochromation. The images were acquired on the prototype TEAM 0.5 microscope, which was developed on a Titan platform by increasing its electrical and mechanical stability.

Electron tomography on micrometer-thick specimens with nanometer resolution.

Transmission electron microscopy (TEM) is a well-established technique to explore matter down to the atomic scale. TEM tomography methods have been developed to obtain volume information at the mesoscopic dimensions of devices or complex mixtures of multiphase objects with nanometer resolution, but these methods are in general only applicable to relatively thin specimens with a few hundred nanometer thickness at most. Here we introduce an approach based on scanning TEM (STEM) tomography that pushes the resolution in three dimensions down to a few nanometers for several micrometer ultrathick specimens using a conventional TEM with 300 kV accelerating voltage, and we demonstrate its versatility for materials research and nanotechnology.

Aberration-corrected microscopy for structural biology applications.

This study explores the potential of a C(s)-corrected transmission electron microscope for structural studies of biological samples, in particular isolated macromolecular complexes. A 300-kV transmission electron microscope, equipped with a C(s) corrector was employed to record sets of images at different defocus and C(s) settings. The experiments were designed to determine whether imaging with large defocus benefits from C(s) correction. Defocus contrast in biological imaging has a stronger influence on image resolution than any other parameter. We find the results are in good agreement with theoretical framework, verifying that the typical imaging conditions required for biological investigations are not affected by C(s) correction.

The structure of 1D CuI crystals inside SWNTs.

Nanocomposites consisting of one-dimensional CuI crystals inside single-walled carbon nanotubes were obtained using the capillary technique. high-resolution transmission electron microscopy investigations of the atomic structure of the encapsulated 1D CuI crystals revealed two types of 1D CuI crystals with growth direction <001> and <110> relative to the bulk hexagonal CuI structure. Atomic structure models were proposed based on the high-resolution transmission electron microscopy images. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms whereas copper atoms, with lower atomic number giving lower contrast, are thought to be statistically distributed.

Detection of single atoms and buried defects in three dimensions by aberration-corrected electron microscope with 0.5-A information limit.

The ability of electron microscopes to analyze all the atoms in individual nanostructures is limited by lens aberrations. However, recent advances in aberration-correcting electron optics have led to greatly enhanced instrument performance and new techniques of electron microscopy. The development of an ultrastable electron microscope with aberration-correcting optics and a monochromated high-brightness source has significantly improved instrument resolution and contrast. In the present work, we report information transfer beyond 50 pm and show images of single gold atoms with a signal-to-noise ratio as large as 10. The instrument's new capabilities were exploited to detect a buried Sigma3 {112} grain boundary and observe the dynamic arrangements of single atoms and atom pairs with sub-angstrom resolution. These results mark an important step toward meeting the challenge of determining the three-dimensional atomic-scale structure of nanomaterials.

Breaking the spherical and chromatic aberration barrier in transmission electron microscopy.

Since the invention of transmission electron microscopy (TEM) in 1932 (Z. Physik 78 (1932) 318) engineering improvements have advanced system resolutions to levels that are now limited only by the two fundamental aberrations of electron lenses; spherical and chromatic aberration (Z. Phys. 101 (1936) 593). Since both aberrations scale with the dimensions of the lens, research resolution requirements are pushing the designs to lenses with only a few mm space in the pole-piece gap for the specimen. This is in conflict with the demand for more and more space at the specimen, necessary in order to enable novel techniques in TEM, such as He-cooled cryo electron microscopy, 3D-reconstruction through tomography (Science 302 (2003) 1396) TEM in gaseous environments, or in situ experiments (Nature 427 (2004) 426). All these techniques will only be able to achieve Angstrom resolution when the aberration barriers have been overcome. The spherical aberration barrier has recently been broken by introducing spherical aberration correctors (Nature 392 (1998) 392, 418 (2002) 617), but the correction of the remaining chromatic aberrations have proved to be too difficult for the present state of technology (Optik 57 (1980) 73). Here we present an alternative and successful method to eliminate the chromatic blur, which consists of monochromating the TEM beam (Inst. Phys. Conf. Ser. 161 (1999) 191). We show directly interpretable resolutions well below 1A for the first time, which is significantly better than any TEM operating at 200 KV has reached before.

[Implantable drug pumps for spinal opioid analgesia: technical solutions and problems]. / Implantierbare Medikamentenpumpen für die Opioid-Analgesie: Technische Lösungen und Probleme.

Among the many technical appliances for pain therapy which are currently available, the use of implantable drug pumps for prolonged pain treatment is of increasing importance. Since this kind of pain therapy can be used without any problems outside the hospital, it improves the quality of life of the patient. Furthermore, it is combined with a reduction of side-effects which frequently occur when analgesics are given orally or parenterally in big single doses. High initial costs are compensated by a good cost-benefit ratio of this kind of pain treatment, which enables the use of analgesics in low doses in out-patients. Based on the use of gas mixtures which can be compressed repeatedly, implantable mechanically-driven pumps are a nearly inexhaustible propulsion unit for drug infusions. The development of new gas mixtures and of innovative control mechanisms allows greater independence from surrounding influences and higher precision regarding infusion rates. Mechanically-driven pumps are characterized by prolonged functioning and low cost of purchase. Therefore, they will continue to be available on the medical market in future. Special progress in cardiac pacemaker therapy as well as further miniaturization of portable infusion pumps with peristaltic propulsion have led to the development of programmed implantable pumps with lithium batteries as energy sources. The advantages of these pumps, particularly those with "externally" programmable infusion rates (continuous, bolus, periodical bolus, etc.) point to the future. With these devices, evacuation and refilling of the pumps due to necessary changes of drug concentrations, as has to be done with mechanically working pumps with fixed infusion rates, are no longer necessary. Therefore, these programmable pumps can also be used for infusion of drug concentrates. At present, however, high costs and the battery-dependent limited duration of functioning of these devices are disadvantageous. As with cardiac pacemakers, battery exchange is necessary. Using implantable drug pumps, relevant changes of body temperature and atmospheric pressure lead to more or less considerable deviations of the infusion rates. These deviations differ from product to product and can be studied in the informative material published by the manufacturer.

Optimization of EDX performance in Tecnai TEMs.

The quality of X-ray spectra from FEGTEMs has been improved by three different means: the use of beryllium shields, improved collimation and improved specimen holder geometry. The improvements lead to a significant increase in peak-to-background ratios and a reduction in spurious peaks in the EDX spectra. A double-tilt, low-background specimen holder was designed to allow EDX analysis at 0 degrees of tilt without shadowing.

High resolution EELS using monochromator and high performance spectrometer: comparison of V2O5 ELNES with NEXAFS and band structure calculations.

Using single crystal V2O5 as a sample, we tested the performance of the new aberration corrected GATAN spectrometer on a monochromatised 200 kV FEG FEI (S)TEM. The obtained V L and O K ELNES were compared with that obtained in a common GATAN GIF and that in the new spectrometer, without monochromatised beam. The performance of the new instrumentation is impressive: recorded with an energy-resolution of 0.22 eV, the V L(3) edge reveals all the features due to the bulk electronic structure, that are also revealed in near-edge X-ray absorption fine structure (NEXAFS) with a much higher energy-resolution (0.08 eV). All features of the ELNES and NEXAFS are in line with a theoretical spectrum derived from band-structure calculations.

Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution.

Near-edge fine structures of the metal L(2,3) and O K-edges in transition metal-oxides have been studied with a transmission electron microscope equipped with a monochromator and a high-resolution imaging filter. This system enables the recording of EELS spectra with an energy resolution of 0.1eV thus providing new near-edge fine structure details which could not be observed previously by EELS in conventional TEM instruments. EELS-spectra from well-defined oxides like titanium oxide (TiO(2)), vanadium oxide (V(2)O(5)), chromium oxide (Cr(2)O(3)), iron oxide (Fe(2)O(3)), cobalt oxide (CoO) and nickel oxide (NiO) have been measured with the new system. These spectra are compared with EELS data obtained from a conventional microscope and the main spectral features are interpreted. Additionally, the use of monochromised TEMs is discussed in view of the natural line widths of K and L(2,3) edges.

[C1-esterase inhibitor in ACE inhibitor-induced severe angioedema of the tongue]. / C1-Esterase-Inhibitor bei ACE-Hemmer-induziertem schwerem Angioödem der Zunge.

Angio-oedema are often massive but temporary swellings of the soft tissue of the face or the throat, which can also affect other regions of the human body (e.g. the skin or internal organs). An oedema of the face and throat represents a life-threatening situation. Apart from the clinical condition of the patient and detailed knowledge of the medical history (incl. medical applications), the treatment should depend on the different pathogenesis. In this reported case, we describe the severe clinical development of an angio-oedema under a long-term treatment with an ACE-inhibitor, which in the end was only successfully treated with the application of a C1 inhibitor concentrate.

[Postoperative nausea and vomiting--still a problem?]. / Postoperative Ubelkeit und Erbrechen--Immer noch ein Problem?

Based on a questionnaire of the General Hospital of Hamburg-Altona, we asked 738 patients about postoperative complaints such as nausea, vomiting, pain in the operating field and feeling of coldness in order to record the quality of the results of operation and anaesthesia in 1997 and 1998. The incidence of nausea and vomiting amounted to only 29% on average. One of our earlier studies of postoperative vomiting from 1995-1997 and the results gained from a control group of non-treated patients in our ondansetron study from 1995, which was conducted using information drawn from the routinely-used anaesthesia protocol and was therefore limited to data from the immediate pre- and postoperative period up to discharge of the patients from the recovery ward, showed much higher frequencies of nausea and vomiting (44 and even 66% on average, respectively). We cannot definitely evaluate whether the reduction in the average rates of nausea and vomiting in our present study is due to the additional preoperative application of 150 mg vomex supp. and 1.0-2.5 mg dehydrobenzperidol and/or 20-30 mg metoclopramid given i.v. shortly before the end of anaesthesia or to more intensive observation of non-medicinal prophylactic possibilities. But when we look at the frequency of nausea and vomiting in special groups of our present study, we can still find unacceptably high rates of nausea and vomiting, for instance 40% after cholecystectomies and abruptios and even 50% after struma operations. This shows that a satisfactory solution to this problem has not yet been found--partly due, unfortunately, to financial restrictions. Nevertheless, for 15% of the patients postoperative nausea and vomiting were of only minor importance for general satisfaction with the treatment given them. This was probably due to good premedication of amnestic after-effects of narcosis.

A myxozoan-like parasite causing xenomas in the brain of the mole, Talpa europaea L., 1758 (Vertebrata, Mammalia).

Light and transmission electron microscopy revealed pericytes of brain capillaries of moles (Talpa europaea L., 1758) as parasitized intracellularly. These host cells were enlarged and of globular or ellipsoid shape, and incorporated a cell-within-cell sequence of primary, secondary and, rarely found, tertiary developmental stages of an eukaryotic organism. Other stages like spores were not discovered either in brain or in other organs. Due to the vertebrate host, and the parasitic cells showing the enveloped state this parasite can be classified as belonging to the Myxozoa rather than Paramyxea. Since spores, which would allow an exact identification of the parasite, could not be detected and mammals are very unusual hosts for Myxozoa, the parasite was designated a myxozoan-like organism.

Inelastic electron holography

Coherence of inelastically scattered electrons was investigated by means of biprism interference experiments performed in a transmission electron microscope equipped with a highly coherent field emission gun and an imaging filter. The experimental results show that within the wave inelastically scattered at aluminium plasmons there is in fact an area of about 10 nm diameter with coherence sufficient to take electron holograms.

Element specific imaging with high lateral resolution: an experimental study on layer structures.

Planar defects and individual layers in ceramic material are chemically imaged by high resolution energy-filtering TEM using a post-column imaging electron energy filter. Objects are barium layers in the cuprate superconductor NdBa2Cu3O7-delta (isostructual to YBa2Cu3O7-delta) as well as planar defects and precipitates of beta-WB in tungsten- and chromium-doped TiB2. The barium layers with a spacing of 0.42 nm in the cuprate are resolved in jump-ratio images using the Ba_N edge. In the boride system the beta-WB precipitates with thickness of 0.8 nm can be chemically imaged in elemental maps of B_K, Ti_L,Cr_L and W_M. The B as well as the Ti map show a decrease in intensity at the precipitates, whereas in the W map an increase in intensity is observed. The boron-deficient layers with a spacing of 0.38 nm in the beta-WB precipitate can be resolved in boron jump-ratio images. Additionally, defects containing single boron-deficient layers are chemically imaged. Hence structures in the dimension of interatomic distances can be imaged with respect to their elemental constituents. Although high resolution electron spectroscopic images contain strong interference contrast from elastic scattering, after normalization or background subtraction the element specific images are dominated by chemical contrast.

Stem cell factor binding to retrovirus primer binding site silencers.

Using modified nuclear lysis and binding conditions, we have examined the binding of an embryonal carcinoma (EC) cell factor, binding factor A, to a stem cell-specific silencer which acts at the DNA level and overlaps the Moloney murine leukemia virus (M-MuLV) proline primer binding site (PBS). Following our protocol, we found that in vitro binding of factor A correlated with the in vivo activity of the M-MuLV silencer. Factor A bound specifically to the wild-type silencer element at room temperature and 30 degrees C, but not at 4 degrees C, and bound 10-fold better to the full-length silencer than to a minimal silencer core element. The factor was enriched in nuclear compared with cytosolic extracts and in undifferentiated EC cells compared with differentiated cells in which the silencer is nonfunctional. Salt and ion requirements for factor A binding were investigated, and partial purification steps indicated the factor to be a heparin-Sepharose-binding moiety of greater than 100 kDa. To examine possible relationships between silencer and PBS activities, sequences representing phenylalanine, isoleucine, lysine-1,2, lysine-3, methionine, and tryptophan PBS DNA fragments were tested in vivo for stem cell-specific repression of M-MuLV expression and in vitro in DNA binding assays. Of these PBS elements, only the lysine-1,2 PBS DNA fragment showed consistently high levels of repression. Interestingly, the lysine-1,2 PBS DNA fragment also formed a complex with an EC cell factor with characteristics similar to those of factor A. However, the two factors did not cross-compete in binding studies, suggesting that they may be different but related factors. Our results suggest that expression of Mason-Pfizer monkey virus, visna virus, and spumavirus, which use the lysine-1,2 PBS, may be inhibited in undifferentiated stem cells.