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Transmission electron microscopy is an indispensable tool in modern materials science. It enables the structure of materials to be studied with high spatial resolution, and thus makes a decisive contribution to the fact that it is now possible to understand the microstructure-related physical and chemical characteristics and to correlate these with the macroscopic materials properties. It was tantamount to a paradigm shift when electron microscopy reached atomic resolution in the late 1990s due to the invention of aberration-corrected electron optics. It is now generally accepted practice to perform picometer-scale measurements and chemical analyses with reference to single atomic units. This review has three objectives. Microscopy in atomic dimensions is applied quantum physics. The consequences of this for practical work and for the understanding and application of the results shall be worked out. Typical applications in materials science will be used to show what can be done with this kind of microscopy and where its limitations lie. In the absence of relevant monographs, the aim is to provide an introduction to this new type of electron microscopy and to enable the reader to access the literature in which special issues are addressed. The paper begins with a brief presentation of the principles of optical aberration correction. It then discusses the fundamentals of atomic imaging and covers typical examples of practical applications to problems in modern materials science. It is emphasized that in atomic-resolution electron microscopy the quantitative interpretation of the images must always be based on the solution of the quantum physical and optical problem on a computer.

Background: To determine if filtration-histogram based texture analysis (MRTA) of clinical MR imaging can non-invasively identify molecular subtypes of untreated gliomas. Methods: Post Gadolinium T1-weighted (T1+Gad) images, T2-weighted (T2) images and apparent diffusion coefficient (ADC) maps of 97 gliomas (54 = WHO II, 20 = WHO III, 23 = WHO IV) between 2010 and 2016 were studied. Whole-tumor segmentations were performed on a proprietary texture analysis research platform (TexRAD, Cambridge, UK) using the software’s freehand drawing tool. MRTA commences with a filtration step, followed by quantification of texture using histogram texture parameters. Results were correlated using non-parametric statistics with a logistic regression model generated. Results: T1+Gad performed best for IDH typing of glioblastoma (sensitivity 91.9%, specificity 100%, AUC 0.945) and ADC for non-Gadolinium-enhancing gliomas (sensitivity 85.7%, specificity 78.4%, AUC 0.877). T2 was moderately precise (sensitivity 83.1%, specificity 78.9%, AUC 0.821). Excellent results for IDH typing were achieved from a combination of the three sequences (sensitivity 90.5%, specificity 94.5%, AUC = 0.98). For discriminating 1p19q genotypes, ADC produced the best results using unfiltered textures (sensitivity 80.6%, specificity 89.3%, AUC 0.811). Conclusion: Preoperative glioma genotyping with MRTA appears valuable with potential for clinical translation. The optimal choice of texture parameters is influenced by sequence choice, tumour morphology and segmentation method.

Since January 2013 the long-distance passenger market is open to bus operators. This paper is about the efforts of the German railway company in market research and model building to predict the effect of bus market liberalisation in advance. Methods, forecast and the real development of the bus market will be shown. The major focus is the design of the situational stated preference conjoint and the parameter estimation of the mode choice model.

In a recent article [1] we examined the influence of the applied electron dose rate on the magnitude of the image contrast in high-resolution transmission electron microscopy (HRTEM). We concluded that the magnitude of the image contrast is not substantially affected by the applied electron dose rate. This result is in obvious contradiction to numerous earlier publications by Kisielowski and coworkers [2-7], who commented our recent article due to this contradiction. The present short communication is a response to the comment of Kisielowski and coworkers on our recent article, where we provide additional arguments supporting our initial findings and conclusions on the magnitude of the image contrast in HRTEM.

The precise characterisation of the instrumental imaging properties in the form of aberration parameters constitutes an almost universal necessity in quantitative HRTEM, and is underlying most hardware and software techniques established in this field. We focus in this paper on the numerical analysis of individual diffractograms as a first preparatory step for further publications on HRTEM aberration measurement. The extraction of the defocus and the 2-fold astigmatism from a diffractogram is a classical pattern recognition problem, which we believe to have solved in a near-optimum way concerning precision, speed, and robustness. The newly gained measurement precision allows us to resolve fluctuations of the defocus and the 2-fold astigmatism and to assess thereby the optical stability of electron microscopes. Quantitative stability criteria are elaborated, which may serve as helpful guidelines for daily work as well as for microscope acceptance tests.

The precise characterisation of the instrumental imaging properties in the form of aberration parameters constitutes an almost universal necessity in quantitative HRTEM, and is underlying most hardware and software techniques established in this field. We focus in this paper on the numerical analysis of individual diffractograms as a first preparatory step for further publications on HRTEM aberration measurement. The extraction of the defocus and the 2-fold astigmatism from a diffractogram is a classical pattern recognition problem, which we believe to have solved in a near-optimum way concerning precision, speed, and robustness. The newly gained measurement precision allows us to resolve fluctuations of the defocus and the 2-fold astigmatism and to assess thereby the optical stability of electron microscopes. Quantitative stability criteria are elaborated, which may serve as helpful guidelines for daily work as well as for microscope acceptance tests.

The structure of the oxygen sub-lattice in Cs 0.5 [Nb 2.5 W 2.5 O 14 ] is investigated for the first time by advanced electron-optical methods. Since Cs 0.5 [Nb 2.5 W 2.5 O 14 ] resembles the crystal structure of the so-called M1 phase of Mo–V–Nb–Te–O, which is the best catalyst for the selective oxidation of propane to acrylic acid, the structure analysis of the oxygen sub-lattice can contribute substantially to a better understanding of this catalytic process. The so far only partially known structure of the complex metal oxide Cs 0.5 [Nb 2.5 W 2.5 O 14 ] is investigated by combining modern methods of high-resolution transmission electron microscopy with crystallographic image processing techniques. Average atom positions in the a – b plane are determined from the phase of the exit-plane wave function, which was numerically reconstructed from a focal series of spherical-aberration-corrected electron micrographs. The experimentally determined atom positions agree well with a structure model obtained by first-principles calculations for the underlying M 5 O 14 (M = Nb, W) framework. Moreover, several deviations from the periodic structure, which may influence the catalytic properties of the structurally similar M1 phase, are observed. The obtained results demonstrate that aberration-corrected high-resolution transmission electron microscopy is a reliable alternative for the analysis of periodic structures, in particular when traditional methods for crystallographic structure determination like XRD or neutron diffraction cannot be applied.

Employing an aberration corrector in a high-resolution transmission electron microscope, the spherical aberration C S can be tuned to negative values, resulting in a novel imaging technique, which is called the negative C S imaging (NCSI) technique. The image contrast obtained with the NCSI technique is compared quantitatively with the image contrast formed with the traditional positive C S imaging (PCSI) technique. For the case of thin objects negative C S images are superior to positive C S images concerning the magnitude of the obtained contrast, which is due to constructive rather than destructive superposition of fundamental contrast contributions. As a consequence, the image signal obtained with a negative spherical aberration is significantly more robust against noise caused by amorphous surface layers, resulting in a measurement precision of atomic positions which is by a factor of 2–3 better at an identical noise level. The quantitative comparison of the two alternative C S -corrected imaging modes shows that the NCSI mode yields significantly more precise results in quantitative high-resolution transmission electron microscopy of thin objects than the traditional PCSI mode.

It is shown that certain zeolites can selectively adsorb representative fermentation inhibitors (5-hydroxymethylfurfural (HMF), furfural and vanillin) from biomass hydrolyzates with minimal loss of sugars improving significantly the ethanol yield of the fermentation process. The potential for recovering the inhibitors for further use as industrially valuable compounds by preferential adsorption on appropriately chosen zeolites is also demonstrated.

Aberration corrected high-resolution transmission electron microscopy is used to determine the reconstruction of atomic bonds of a 90 ∘ [1 0 0] grain boundary in YBa 2 Cu 3 O 7 - δ . A precise measurement of atom positions within the grain boundary and the assessment of the oxygen stoichiometry require at the same time a high control of residual lens aberrations of the electron microscope and a good signal-to-noise ratio. This goal is achieved by the combination of spherical-aberration correction in the microscope with the numerical exit-plane wave function reconstruction from focal series. Atomic column positions for individual cations and anions are determined by the regression analysis of peak maxima in the phase image of the retrieved exit-plane wave function. The measurement accuracy is quantitatively assessed, including the statistical error related to residual noise. Changes in bondlengths between copper atoms and the apical oxygen are measured, indicating the distortion of the square pyramidal oxygen coordination of plane copper sites and the square coordination of chain copper sites in the grain boundary.

As-fired thick-film resistors have the resistance tolerance within ±20% and this tolerance is increased for smaller components. Therefore the novel trimming methods are necessary for microresistors, especially when they are embedded in LTCC substrate. This paper compares electrical (normalized temperature dependence of resistance, low frequency noise) and stability properties (relative resistance drift, changes of current noise index) of untrimmed, voltage pulse trimmed and laser trimmed unglazed thick-film resistors after step-increased long-term thermal ageing at 162 °C, 207 °C and 253 °C. Moreover the effect of long term exposure (1000 h, 125 °C) and thermal shocks (1000 shocks between −55 °C and 125 °C) is analysed for untrimmed and voltage pulse trimmed buried LTCC resistors.

Rationale and objectives Introduction of combination of the segmentation tool SegoMeTex and the virtual endoscopy system VIVENDI to perform virtual endoscopic inspections of the human lung. This virtual bronchoscopy system enables visualization of the tracheobronchial tree down to seventh generation. Furthermore, the modified virtual system visualizes hidden structures such as segmented vascular system or tumors. Materials and methods The segmentation is based on image data acquired by a multislice computed tomography scanner. SegoMeTex is used to segment the tracheobronchial tree by a hybrid system with minimal user action. Similarly, the complementary pulmonary arterial can be segmented, whereas additional structures such as tumors are marked manually. On this dataset, subsequently, data structures of the inner surface for virtual endoscopy are generated. Finally, the dataset can be explored by a virtual bronchoscopy procedure using the VIVENDI system. Results The segmentation method was successfully tested on 22 patients. The hybrid segmentation system identified bronchi up to the sixth generation with a sensitivity of more than 58%, and a positive predictive value of more than 90%. After the segmentation, the datasets are explored interactively (>30 fps on a standard personal computer platform in real-time rendering) using the virtual endoscopy software. The exploration exposed a high-quality reconstruction, even of small structures throughout the dataset. Conclusion Virtual bronchoscopy in combining with a highly sensitive segmentation is a valuable tool for the localization and measurement of stenosis for resection planning.

A novel design of gas sensor using low temperature cofired ceramics (LTCC) and thin film technologies is presented. The LTCC structure is composed essentially of two ceramic layers with interlayer thick film Pt heater, interdigitated electrodes on top, contact pads and metallic connections realised by vias. The thin films of both SnO2 and In2O3, intentionally doped and activated, were deposited on top of the structure. With some modifications of the lamination process and heat treatment parameters, the authors obtained the upper ceramic layer with the roughness not exceeding 250 nm, what was suitable for thin film technology. The films deposited onto such LTCC structure revealed the sensing properties very similar to the reference films deposited onto glass. The gas-sensitive films were tested with changing concentrations of reducing and oxidising gases in air. The necessary sensor working temperature was obtained and stabilised using a custom-built digital controller. The low heat capacity of the sensor structure enabled also a sinusoidal temperature control. The satisfactory results obtained by the authors indicate that the connection of LTCC and thin film technologies can lead to the fabrication of good quality gas sensors.

The tracheobronchial tree as part of the lung is part of one of the most important organs of the human body. Inhaled air is distributed to the alveolus where oxygen and carbon dioxide exchange between air and blood takes place. In this paper, we introduce the virtual endoscopy system VIVENDI to perform virtual inspections of tracheobronchial trees based on their segmentation and of the complementing blood vessels. It is based on a hybrid segmentation pipeline which enables the segmentation of vascular and tracheobronchial structures down to the seventh generation of the bronchi.

Recently an electromagnetic hexapole system for the correction of the spherical aberration of the objective lens of a 200 kV transmission electron microscope has been constructed by Haider and coworkers. By appropriately exciting the hexapole elements it is possible to adjust specific values of the spherical aberration coefficient ranging from the value of the original uncorrected instrument over zero even to negative values. In the first part of the paper the consequences of the tunable spherical aberration are investigated. New imaging modes are available: By adjustment of an optimum value for the spherical-aberration coefficient, the point resolution of phase-contrast imaging can be extended to the information limit. Phase-contrast imaging can be improved by a reduced level of contrast delocalisation. For zero aberration contrast delocalisation does not occur. In this case high-resolution investigations are carried out under amplitude-contrast conditions, where the local image intensity of crystalline objects is controlled by electron diffraction channelling. The defocus and spherical aberration values related to the new imaging modes are given. In the second part novel applications of the instrument to semiconductor heterostructures and ceramic grain boundaries are examined.

This paper presents systematic investigations of electrical and stability properties of various low temperature co-fired ceramics (LTCC) resistors. One of the goals of this work was to check the compatibility of LTCC materials (tapes, resistive and conductive inks) from various manufacturers. Three commercially available green tapes and three LTCC resistor/conductor systems were examined. The resistive inks with 1 k Ω/ sq . nominal sheet resistance were used. Buried (inside) and surface resistors were laminated and fired according to the tape manufacturers’ recommendations. The influence of dimensional effect on sheet resistance and hot temperature coefficient of resistance, the temperature dependence of resistance in a wide temperature range (from −180°C to +130°C), long-term stability of thermally aged as-fired resistors (150°C, 500 h) and durability to high-voltage micro- or nanosecond pulses (50 ns pulses with 4000 V/mm maximum electric field or 10 μs ones with 700–1000 V/mm electrical field) were carried out for electrical and stability characterisation of LTCC resistors. Non-destructive scanning acoustic microscope diagnostics was applied for structure investigation and estimation of lamination and cofiring process quality of buried LTCC resistors.

The sensitivity of a capacitive penicillin sensor based on a pH-sensitive electrolyte–insulator–semiconductor (EIS) sensor with respect to four different kinds of penicillin is investigated. A total of 10 μl of a solution containing penicillin G, ampicillin, amoxicillin or cloxacillin, respectively, are dried on a plastic disc as a diffusion barrier which is then brought in contact with the sensor. In order to correct the sensor signals for a possible pH interference, all measurements are performed with a penicillin sensor as well as with a pH sensor. The resulting calibration curves show no sensitivity for cloxacillin and nearly equal sensitivities for the other three kinds of penicillin. Lower detection limits of about 0.05 μg are obtained for penicillin G, ampicillin and amoxicillin.

Chemical sensors with structured and porous semiconductor/insulator capacitors have been developed. The sensors have been prepared using standard techniques of semiconductor processing, i.e. by means of an anisotropic and anodic etching process, respectively. Both sensor types exhibit a high, near-Nernstian pH sensitivity of about 54 mV per pH decade. Due to the enlargement of the active sensor area, the measured capacitance values increase up to a factor of 30. These structured and porous electrolyte–insulator–semiconductor (EIS) sensor substrates are suitable as transducer material for biosensors which has been demonstrated by depositing the enzyme penicillinase through physical adsorption onto the respective pH-sensitive EIS capacitors.

Two methods for the immobilisation of enzymes on silicon-based so-called electrolyte–insulator–semiconductor (EIS) structures are suggested. These EIS structures are used as a basis for potentiometric biosensors. In the first method, heterobifunctional cross-linker molecules are employed to covalently bind enzymes to these capacitive layer structures which possess a planar surface that contains amine groups. Porous EIS sensors which, in comparison to planar sensors, exhibit an enlarged surface area, are used in the second method. For the first time, pH-sensitive Si3N4 was deposited on the walls and bottoms of the SiO2-covered pores. Here, a large amount of enzyme molecules can adsorptively be bound inside the porous structure. Penicillinase is used as a model enzyme. Capacitance–Voltage and Constant Capacitance measurements are performed in order to examine the respective penicillin sensor responses and thus to validate both immobilisation methods. Whereas the sensitivity of the sensors prepared by both methods is nearly identical for low penicillin concentrations up to around 0.25 mM, a difference of the calibration curves in the higher concentration range indicates a larger amount of immobilised enzyme in the case of the porous structures.

Due to the influence of three-fold astigmatism, the spatial resolution obtained on many modern high-resolution transmission electron microscopes is often not better than 0.2 nm. Although beam tilt can mask the effect of three-fold astigmatism when imaging periodic specimens, the correction of three-fold astigmatism is required for obtaining isotropic ultra-high resolution (≤0.15 nm). Three-fold astigmatism also hampers the correct alignment of the microscope, resulting in additional beam tilt and two-fold astigmatism, and consequently in a further loss of resolution. The amount of three-fold astigmatism of an instrument is found to be stable for periods well in excess of a year. After hardware correction through excitation of a magnetic hexapole in the objective lens stigmator unit of our Philips CM300ST FEG, we reduced the magnitude of the three-fold astigmatism from a value of 1.1 μm, for this particular instrument, to less than 0.1 μm, a value at which it allows at least 0.1-nm spatial resolution. Additionally, we show that the micrscope can now be properly aligned for ultra-high-resolution experiments using the standard manual alignment procedures.

A new capacitive field-effect microsensor based on a porous EIS (electrolyte-insulator-semiconductor) structure is presented. The porous silicon sensor was prepared using standard techniques of semiconductor processing. A well-defined macroporous layer was formed on silicon by electrochemical etching and a SiO 2 Si 3 N 4 sandwich was deposited as insulating and pH-sensitive layer. The porous sensor exhibits a high, near-Nernstian pH sensitivity of about 54 mV per decade in the concentration range from pH 4 to pH 8, similar to a planar non-porous EIS structure with the same layer sequence. The enlargement of the active sensor area (surface) due to the porous structure increases the measured capacitance and thus allows a scaling down of the sensor. The preparation of biosensors based on the same structure is demonstrated by immobilization of the enzyme penicillinase as biosensitive component.

Phase-retrieval methods in high-resolution transmission electron microscopy allow one to determine the wave function at the exit-plane of the object (the exit-plane wave function). Viable methods for the retrieval of the exit-plane wave function are off-axis electron holography and focal-series reconstruction. In the framework of these methods, attention has been directed so far mostly at the correction of the wave function with respect to the “main” contributions to the aberration function, which are caused by the spherical aberration and by the defocusing of the objective lens. We describe a procedure which allows to measure and correct routinely for all relevant residual aberrations which may be present due to possible beam misalignment, 2-fold or 3-fold astigmatism. Using focal-series reconstruction it is demonstrated that a substantial gain in interpretable resolution can be observed in the retrieved wave function by taking into account these additional aberration effects.

The antiherpes virostatics acyclovir (ACV), valaciclovir (VACV), penciclovir (PCV), famciclovir (FCV) and ganciclovir (GCV), which belong to the group of purine acyclic nucleoside analogues, were tested for clastogenic and sister chromatid exchange (SCE)-inducing activity in Chinese hamster V79-E cells upon chronic application with and without a recovery period. ACV induced borderline effects in both cytogenetic assays, a dose-dependent reduction of the mitotic index and an increasing cell cycle delay. With VACV and PCV only a decrease of the mitotic index and an increase of cell cycle delay were observed. FCV was negative with respect to the four parameters studied, presumably due to the incapacity of the target cells of metabolizing FCV to PCV. GCV was a very potent genotoxin in both assays. It induced a statistically significant SCE response even in the range of the cytomegalovirus IC50 of < 10 μM. By variation of the experimental protocol it was shown that SCEs are induced in the second cell cycle following exposure to GCV but not in the first one. It is assumed that the drugs under study are metabolized to their respective triphosphates and then inhibit DNA replication as detected by decreasing mitotic index and increasing cell cycle delay. In the case of GCV it is suggested that GCV-TP is incorporated into the target cell DNA and that chromosomal aberrations and SCEs are secondary lesions due to repair processes at the substituted template.

A penicillin-sensitive potentiometric biosensor with a high long-term stability was fabricated by immobilizing penicillinase on top of a pH-sensitive electrolyte/insulator/semiconductor (EIS) layer structure made of Al/p-Si/SiO 2 /Si 3 N 4 . The immobilization was performed in two distinct steps with a heterobifunctional cross-linker. In the first step the amine-specific functional group of the cross-linker molecules was linked directly to the Si 3 N 4 surface. Subsequently, the second reactive group of the fixed cross-linker molecules was made to bind to the enzyme. This immobilization procedure avoids a reduction of activity due to intermolecular cross-linking of the enzyme and results in sensor devices with a high long-term stability of at least 250 days. Sensitivities of about 60 mV per decade of penicillin concentration were obtained from C/V (capacitance/voltage) and CONCAP (constant capacitance) measurements.

The first example of a direct enzymatic coupling of two different, sterically demanding Cα-fluoroalkyl amino acids to amino acid nucleophiles is reported. N-Protected Ala methyl ester derivatives bearing a methyl-, difluoromethyl-, or trifluoromethyl group, respectively, instead of the α-proton were accepted as substrates by carboxypeptidase Y and could, therefore, be coupled directly to various nucleophiles.

Starting from hexafluoroacetone-protected ( S )-glutamic acid, trans -5-fluoropipecolic and 5,5-difluoropipecolic acid have been synthesized. The piperidine ring was constructed by an intramolecular metal carbenoid NH insertion.

Two different numerical procedures, an algorithm based on the method of simulated annealing as well as a genetic algorithm, are applied for the full non-linear reconstruction of the exit plane wave function belonging to periodic areas of high-resolution electron microscopy images. Using simulated high-resolution images of the intermetallic alloy Ni 4 Mo as a test case, the convergence behaviour and the accuracies of both algorithms are investigated. Based on processed experimental high-resolution images of this alloy, a practical example of the reconstruction of the exit plane wave function is given.

Zone-axis and off-zone-axis illumination were used to observe the compositional modulation of ( YBa 2 Cu 3 O 7 ) m /( PrBa 2 Cu 3 O 7 ) n superlattices by means of high-resolution transmission electron microscopy. In both cases a chemically sensitive image contrast allowing a distinction between Y and Pr occupancy was obtained. The optimum parameters for imaging the compositional difference between YBa 2 Cu 3 O 7 and PrBa 2 Cu 3 O 7 were evaluated by means of detailed image simulations. Good agreement between experimental images of ( YBa 2 Cu 3 O 7 ) m /( PrBa 2 Cu 3 O 7 ) n superlattices obtain ed with these parameters and the corresponding simulated images was found. Both zone-axis and off-zone-axis imaging are compared and discussed with respect to their ability to yield the strongest possible chemical signal over the widest possible specimen area.

Novel electrochemical sensors with structured and porous semiconductor/insulator capacitors, which allow an efficient miniaturization, have been developed. These sensors have been prepared using standard techniques of semiconductor processing. Both sensor types exhibit a high, near-Nernstian pH sensitivity of about 54 mV per decade. Due to the enlargement of the active sensor area, the measured capacitance values increase up to a factor of 30.