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The concept of electronic orbitals has enabled the understanding of a wide range of physical and chemical properties of solids through the definition of, for example, chemical bonding between atoms. In the transmission electron microscope, which is one of the most used and powerful analytical tools for high‐spatial‐resolution analysis of solids, the accessible quantity is the local distribution of electronic states. However, the interpretation of electronic state maps at atomic resolution in terms of electronic orbitals is far from obvious, not always possible, and often remains a major hurdle preventing a better understanding of the properties of the system of interest. In this review, the current state of the art of the experimental aspects for electronic state mapping and its interpretation as electronic orbitals is presented, considering approaches that rely on elastic and inelastic scattering, in real and reciprocal spaces. This work goes beyond resolving spectral variations between adjacent atomic columns, as it aims at providing deeper information about, for example, the spatial or momentum distributions of the states involved. The advantages and disadvantages of existing experimental approaches are discussed, while the challenges to overcome and future perspectives are explored in an effort to establish the current state of knowledge in this field. The aims of this review are also to foster the interest of the scientific community and to trigger a global effort to further enhance the current analytical capabilities of transmission electron microscopy for chemical bonding and electronic structure analysis. [ABSTRACT FROM AUTHOR]

A major challenge in the growing field of bioelectronic medicine is the development of tissue interface technologies promoting device integration with biological tissues. Materials based on organic bioelectronics show great promise due to a unique combination of electronic and ionic conductivity properties. In this review, we outline exciting developments in the field of organic bioelectronics and demonstrate the medical importance of these active, electronically controllable materials. Importantly, organic bioelectronics offer a means to control cell-surface attachment as required for many device-tissue applications. Experiments have shown that cells readily attach and proliferate on reduced but not oxidized organic bioelectronic materials. In another application, the active properties of organic bioelectronics were used to develop electronically triggered systems for drug release. After incorporating drugs by advanced loading strategies, small compound drugs were released upon electrochemical trigger, independent of charge. Another type of delivery device was used to achieve well-controlled, spatiotemporal delivery of cationic drugs. Via electrophoretic transport within a polymer, cations were delivered with single-cell precision. Finally, organic bioelectronic materials are commonly used as electrode coatings improving the electrical properties of recording and stimulation electrodes. Because such coatings drastically reduce the electrode impedance, smaller electrodes with improved signal-to-noise ratio can be fabricated. Thus, rapid technological advancement combined with the creation of tiny electronic devices reacting to changes in the tissue environment helps to promote the transition from standard pharmaceutical therapy to treatment based on 'electroceuticals'. Moreover, the widening repertoire of organic bioelectronics will expand the options for true biological interfaces, providing the basis for personalized bioelectronic medicine. [ABSTRACT FROM AUTHOR]

• Vortex generation with a pair of quadrupoles. • Analytic treatment of general asymmetric generators. • Multi scale wave optical simulation of entire TEM column. In optics, mode conversion is an elegant way to switch between Hermite Gaussian and Laguerre Gaussian beam profiles and thereby impart orbital angular momentum onto the beam and to create vortices. In optics such vortex beams can be produced in a setup consisting of two identical cylinder lenses. In electron optics, quadrupole lenses can be used for the same purpose. Here we investigate generalized asymmetric designs of a quadrupole mode converter that may be realized within the constraints of existing electron microscopes and can steer the development of dedicated vortex generators for high brilliance electron vortex probes of atomic scale. [ABSTRACT FROM AUTHOR]

Interaction of the probe with the specimen in an electron microscope inevitably leads to entanglement between the probe and the scatterer. In spite of the importance of entanglement in many areas of modern physics, this subject has not been touched in the literature. Here, we develop some ideas about entanglement in electron microscopy for a number of scattering mechanisms. The relationship between entropy, density matrices, and coherence is discussed. In addition, we explore the questions “Why is Bragg scattering coherent and energy loss incoherent?” and “When does decoherence play a role?” It seems to be possible to measure decoherence on extremely short timescales of ∼ 10 − 8 s . This is especially important in view of recent developments in ultrafast electron microscopy. [ABSTRACT FROM AUTHOR]

Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for studying magnetic properties on the nanoscale. However, the classical EMCD technique is notorious for its low signal-to-noise ratio (SNR), which is why many experimentalists have adopted a convergent-beam approach. Here, we study the theoretical possibilities of using a convergent beam for EMCD. In particular, we study the influence of detector positioning as well as convergence and collection angles on the detectable EMCD signal. In addition, we analyse the expected SNR and give some guidelines for achieving optimal EMCD results. [ABSTRACT FROM AUTHOR]

We discuss the feasibility of detecting spin polarized electronic transitions with a vortex filter. This approach does not rely on the principal condition of the standard electron energy-loss magnetic chiral dichroism (EMCD) technique, the precise alignment of the crystal in order to use it as a beam splitter, and thus would pave the way for the application of EMCD to new classes of materials and problems, like amorphous magnetic alloys and interface magnetism. The dichroic signal strength at the L 2, 3 -edge of ferromagnetic Cobalt (Co) is estimated on theoretical grounds using a single atom scattering approach. To justify this approach, multi-slice simulations were carried out in order to confirm that orbital angular momentum (OAM) is conserved in amorphous materials over an extended range of sample thickness and also in very thin crystalline specimen, which is necessary for the detection of EMCD. Also artefact sources like spot size, mask tilt and astigmatism are discussed. In addition, the achievable SNR under typical experimental conditions is assessed. [ABSTRACT FROM AUTHOR]

Standard electron optics predicts Larmor image rotation in the magnetic lens field of a TEM. Introducing the possibility to produce electron vortex beams with quantized orbital angular momentum brought up the question of their rotational dynamics in the presence of a magnetic field. Recently, it has been shown that electron vortex beams can be prepared as free electron Landau states showing peculiar rotational dynamics, including no and cyclotron (double-Larmor) rotation. Additionally very fast Gouy rotation of electron vortex beams has been observed. In this work a model is developed which reveals that the rotational dynamics of electron vortices are a combination of slow Larmor and fast Gouy rotations and that the Landau states naturally occur in the transition region in between the two regimes. This more general picture is confirmed by experimental data showing an extended set of peculiar rotations, including no, cyclotron, Larmor and rapid Gouy rotations all present in one single convergent electron vortex beam. [ABSTRACT FROM AUTHOR]

Abstract: We discuss the feasibility of detecting magnetic transitions with focused electron vortex probes, suggested by selection rules for the magnetic quantum number. We theoretically estimate the dichroic signal strength in the L2,3 edge of ferromagnetic d metals. It is shown that under realistic conditions, the dichroic signal is undetectable for nanoparticles larger than . This is confirmed by a key experiment with nanometer-sized vortices. [Copyright &y& Elsevier]

Abstract: We demonstrate how the mixed dynamic form factor (MDFF) can be interpreted as a quadratic form. This makes it possible to use matrix diagonalization methods to reduce the number of terms that need to be taken into account when calculating the inelastic scattering of electrons in a crystal. It also leads in a natural way to a new basis that helps elucidate the underlying physics. The new method is applied to several cases to show its versatility. In particular, predictions are made for directly imaging atomic orbitals in crystals. [Copyright &y& Elsevier]

Abstract: We report site-specific energy loss magnetic dichroism measurements of the technologically interesting Heusler alloy Ni2MnSn. In addition, we confirm the theoretical prediction that under certain conditions, two different atoms on inequivalent lattice sites give dichroic signals with opposite signs. With this, it is possible to distinguish the magnetic moments of atomic columns that are merely 1.5Å apart using a conventional transmission electron microscope without the need for aberration corrections. [Copyright &y& Elsevier]

Abstract: The validity of the dipole approximations commonly used in the inelastic scattering theory for transmission electron microscopy is reviewed. Both experimental and numerical arguments are presented, emphasizing that the dipole approximations cause significant errors of the order of up to 25% even at small momentum transfer. This behavior is attributed mainly to non-linear contributions to the dynamic form factor due to the overlap of wave functions. [Copyright &y& Elsevier]

Abstract: In this work, the theoretical framework for energy-loss magnetic chiral dichroism (EMCD) is reviewed and a new, fast, and easy-to-use software package is presented. This software is used to simulate the dependence of the EMCD signal on various parameters such as sample thickness and sample tilt. The results are found to be in excellent agreement with other theoretical predictions and experimental data. Furthermore, it is shown that the simulations are fast enough for the planning of experiments “on-the-fly” and for live didactic demonstrations. [Copyright &y& Elsevier]

Treating Coulomb scattering of two free electrons in a stationary approach, we explore the momentum and spin entanglement created by the interaction. We show that a particular discretisation provides an estimate of the von Neumann entropy of the one-electron reduced density matrix from the experimentally accessible Shannon entropy. For spinless distinguishable electrons the entropy is sizeable at low energies, indicating strong momentum entanglement, and drops to almost zero at energies of the order of 10 keV when the azimuthal degree of freedom is integrated out, i.e. practically no entanglement and almost pure one-electron states. If spin is taken into account, the entropy for electrons with antiparallel spins should be larger than in the parallel-spin case, since it embodies both momentum and spin entanglement. Surprisingly, this difference, as well as the deviation from the spin-less case, is extremely small for the complete scattering state. Strong spin entanglement can however be obtained by post-selecting states at scattering angle π /2. [ABSTRACT FROM AUTHOR]

According to theory, x-ray magnetic circular dichroism in a synchrotron is equivalent to energy loss magnetic chiral dichroism (EMCD) in a transmission electron microscope (TEM). After a synopsis of the development of EMCD, the theoretical background is reviewed and recent results are presented, focusing on the study of magnetic nanoparticles for ferrofluids and Heusler alloys for spintronic devices. Simulated maps of the dichroic strength as a function of atom position in the crystal allow evaluating the influence of specimen thickness and sample tilt on the experimental EMCD signal. Finally, the possibility of direct observation of chiral electronic transitions with atomic resolution in a TEM is discussed. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Quantized Orbital Angular Momentum Transfer and Magnetic Dichroism in the Interaction of Electron Vortices with Matter" by Lloyd, Babiker and Yuan.

Purpose: To describe the origin of the vessels supplying the anterior sub-axial cervical vertebrae (C3–C7) to further understand their potential influence on anterior bone loss after anterior cervical spinal surgery. Method: Cadaveric dissection was performed on ten adult human necks after latex perfusion of their subclavian, common carotid and vertebral arteries. The nutrient vessels of the sub-axial cervical spine were identified and traced to their origin. The course and distribution of these vessels and their nutrient foraminae are described. Results: In all cases the anterior nutrient vessels were derived from the thyro-cervical trunk with branches that passed over the longus coli muscles forming a leash of vessels in the pre-vertebral fascia which subsequently extended in a frond-like pattern to pass onto the anterior aspect of vertebrae. The more cranial the cervical level the fewer the number of nutrient vessels and foraminae. The distribution of the foraminae on the anterior vertebral body followed the oblique supero-medial course of the nutrient vessels. Conclusion: Nutrient vessels perforate the cervical vertebrae on their anterior surface. These are derived from a leash of vessels that lie within the pre-vertebral fascia overlying the longus coli muscles. The origin of these vessels is the ascending cervical artery with a variable contribution from the transverse cervical artery. [ABSTRACT FROM AUTHOR]

In this study, we report on the properties of amorphous hydrogenated silicon nitride (a-SiN x :H) thin films synthesized by inductively coupled plasma enhanced chemical vapour deposition (ICP-CVD), combined with an auxiliary capacitively coupled plasma excitation. Physical properties, such as the deposition rate, refractive index and film stress, as well as the chemical composition, microstructure and etch resistance of the samples were investigated. Depending on the capacitively coupled plasma power P RF , two regions can be distinguished which are dominated either by an increased generation of plasma radicals or by an enhanced ion bombardment. At P RF = 35 W, a maximum in the deposition rate is observed as well as an abrupt change in the chemical composition, resulting in an extremely high (>2.5 GPa) compressive stress, in comparison to the layers deposited with P RF = 0. In addition, the wet etch rate in hydrofluoric acid (HF) decreases substantially. Above, up to P RF = 150 W, ion bombardment of the growing film surface is more pronounced due to an increased self-bias of the substrate decreasing the effective deposition rate. Fourier-transform infrared spectroscopy measurements indicate that this behaviour is in close relation to the N H bond density in the samples. Additionally, the continuous increase of the refractive index and Si H bond density, accompanied by the redshift of the Si N infrared absorption peak show that with higher P RF the Si content of the films increases. [ABSTRACT FROM AUTHOR]

Abstract: The holographic mask technique is used to create freely moving electrons with quantized angular momentum. With electron optical elements they can be focused to vortices with diameters below the nanometer range. The understanding of these vortex beams is important for many applications. Here, we produce electron vortex beams and compare them to a theory of electrons with topological charge. The experimental results show excellent agreement with simulations. As an immediate application, fundamental experimental parameters like spherical aberration and partial coherence are determined. [Copyright &y& Elsevier]

Wutte N, Berghold A, Löffler S, Zenz W, Daghofer E, Krainberger I, Kleinert G, Aberer E. CXCL13 chemokine in pediatric and adult neuroborreliosis. Acta Neurol Scand: 2011: 124: 321-328. © 2011 John Wiley & Sons A/S. Objectives - Diagnosis of Lyme neuroborreliosis (NB) depends on the proof of intrathecal antibody production against Borrelia burgdorferi. CXCL13 has been seen to be elevated early in NB, before antibody production has started. In this study, we determined the diagnostic role of the CXCL13 chemokine in cerebrospinal fluid (CSF) and serum for the first time in pediatric NB patients as well as in adults, compared to controls and blood donors (BD). Material and methods - CXCL13 levels were measured in CSF and serum of 33 children and 42 adult patients. Serum CXCL13 was measured in 300 BD. Results - CSF CXCL13 levels were significantly elevated in definite and probable acute NB in children and adults compared to seropositive and seronegative neurological controls ( P < 0.001). Serum CXCL13 levels showed great fluctuations and were not significantly elevated in NB patients. Conclusions - Our study suggests that CSF CXCL13 can be used as a diagnostic marker for NB in children as well. In contrast, CXCL13 serum levels show great variance even in the healthy population and are not indicative of active NB. [ABSTRACT FROM AUTHOR]

Background: The influence of personality on health-related quality of life in patients with multiple sclerosis has been the focus of previous studies showing that introversion and neuroticism were related with reduced health related quality of life. However, no data exist on the impact of temperament on quality of life in this patient group. Methods: Between April 2014 and March 2016 139 multiple sclerosis patients were recruited from a specialized outpatient clinic of the general hospital of Vienna. Health-related quality of life was measured by "The Multiple Sclerosis International Quality of Life Questionnaire (MusiQol)", temperament by "Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Questionnaire – Münster version" (briefTEMPS-M), and disability by the "Expanded disability status scale". All patients underwent a diagnostic psychiatric semi-structured interview (MINI). Results: Known predictors (like disease duration, EDSS, psychiatric co-morbidities, immunomodulatory treatments) explain the proportion of variation in the outcome of MusiQol global index score in 30.9% in multi-variable linear regression analysis. It increased respectively to 40.3, 42.5, and 45.8% if adding the depressive, cyclothymic, or hyperthymic temperament to the list of variables. An increase of depressive and cyclothymic temperament scores significantly reduced global index score of MusiQol (p = 0.005, p = 0.002, respectively), while the hyperthymic temperament significantly raised it (p < 0.001). Conclusion: In MS patients, the depressive and cyclothymic temperament predict a lower and hyperthymic temperament an increased health-related quality of life, independent of current disability status, immunomodulatory treatments, and affective co-morbidities. [ABSTRACT FROM AUTHOR]

A strain characterization technique based on Moiré interferometry in a scanning transmission electron microscope (STEM) and geometrical phase analysis (GPA) method is demonstrated. The deformation field is first captured in a single STEM Moiré hologram composed of multiple sets of periodic fringes (Moiré patterns) generated from the interference between the periodic scanning grating, fixing the positions of the electron probe on the sample, and the crystal structure. Applying basic principles from sampling theory, the Moiré patterns arrangement is then simulated using a STEM electron micrograph reference to convert the experimental STEM Moiré hologram into information related to the crystal lattice periodicities. The GPA method is finally applied to extract the 2D relative strain and rotation fields. The STEM Moiré interferometry enables the local information to be de-magnified to a large length scale, comparable to what can be achieved in dark-field electron holography. The STEM Moiré GPA method thus extends the conventional high-resolution STEM GPA capabilities by providing comparable quantitative 2D strain mapping with a larger field of view (up to a few microns). [ABSTRACT FROM AUTHOR]

The transition from (inter)metallic to substoichiometric regime and therewith associated microstructural modifications within arc evaporated Al-Cr-based oxide coatings was investigated. The dense columnar intermetallic structure is subject to grain refinement when increasing the O 2 flow rate during the deposition. Cr-rich, O-depleted crystalline domains (initially short columnar, then equiaxed globular) and an amorphous Al- and O-enriched boundary phase develops—with increasing volume fraction for higher O 2 flow rates. Such nanocomposites, originating from preferred oxide phase formation of Aluminium, can effectively be adjusted by the amount of oxygen and the nominal cathode composition used during synthesis. [ABSTRACT FROM AUTHOR]

We studied the crystal growth process of type-I transition metal clathrates in two different regimes: a regime of moderate cooling rate, realized with the floating zone technique, and a regime of ultra rapid cooling, realized by the melt spinning technique. In the former regime, bulk Ba8AuxSi46-x and Ba8Cu4.8GaxGe41.2-x single crystals were grown. We investigated segregation effects of the constituting elements by measurements of the composition profiles along the growth direction. The compositional non-uniformity results in a spatial variation of the electrical resistivity which is discussed as well. Structural features of clathrates and their extremely low thermal conductivities imply specifics in growth behavior which manifest themselves most pronouncedly in a rapid crystallization process. Our melt spinning experiments on Ba8Au5Si41 and Ba8Ni3.5Si42.5 (and earlier on some other clathrates) have revealed surprisingly large grains of at least 1 μm. Because of the anomalously high growth rate of the clathrate phase the formation of impurity phases is considerably kinetically suppressed. We present our scanning and transmission electron microscopy investigations of melt spun samples and discuss structural, thermodynamic and kinetic aspects of the unusual clathrate nucleation and crystallization. [ABSTRACT FROM AUTHOR]

Understanding surface receptor clustering and redistribution processes at the cell-matrix contact zone requires detailed knowledge of the spatial integration of these molecules in the architecture of this complex interface. Here we present and discuss critically a procedure to extract such information combining reflection contrast microscopy (RCM) and reflection interference microscopy (RIM). As model system, we used living human umbilical vein endothelial cells (HUVEC) adhering to laminin-coated surfaces and investigated the distribution of the α 2 β 1 (CD29/CD49b) integrin at the contact zone of these cells. First, we applied freeze-fracture electron microscopy to gain information on microscopic details of the α 2 β 1 distribution at the contact zone. Next, we visualized and analyzed the overall lateral distribution of the integrins applying RCM using immunogold-labeling with 10 nm labels and a special silver enhancement technique. We found that RCM can be used to determine the lateral position of the marked receptor molecules to an accuracy of about 100-200 nm, instead of large morphological changes at the contact zone during silver enhancement. Finally, we combined RCM with RIM and analyzed the interference pattern of the contact zone around the label positions. Thus, we were able to detect changes of the average shape of the cell membrane due to receptor-ligand bonding of a size down to the resolution of the techniques. [ABSTRACT FROM AUTHOR]

In light optics, beams with orbital angular momentum (OAM) can be produced by employing a properly-tuned two-cylinder-lens arrangement, also called π /2 mode converter. It is not possible to convey this concept directly to the beam in an electron microscope due to the non-existence of cylinder lenses in commercial transmission electron microscopes (TEMs). A viable work-around are readily-available electron optical elements in the form of quadrupole lenses. In a proof-of-principle experiment in 2012, it has been shown that a single quadrupole in combination with a Hilbert phase-plate produces a spatially-confined, transient vortex mode. Here, an analogue to an optical π /2 mode converter is realized by repurposing a CEOS DCOR probe corrector in an aberration corrected TEM in a way that it resembles a dual cylinder lens using two quadrupoles. In order to verify the presence of OAM in the output beam, a fork dislocation grating is used as an OAM analyser. The possibility to use magnetic quadrupole fields instead of, e.g., prefabricated fork dislocation gratings to produce electron beams carrying OAM enhances the beam brightness by almost an order of magnitude and delivers switchable high-mode purity vortex beams without unwanted side-bands. • Experimental realization of a π /2 mode converter that produces an electron vortex beam using a Hilbert phase plate and a dual quadrupole setup. • Verification of the orbital angular momentum (OAM) content using a binary holographic vortex mask as an OAM analyser. • Wave optical simulations further verified the OAM content and the high mode purity of >80%. • 7.5-fold higher beam brightness compared to the holographic vortex mask technique. [ABSTRACT FROM AUTHOR]

[Display omitted] • Perovskite catalysts with varying A- and B-site doping for reverse water-gas shift. • Operando X-ray diffraction during reverse water gas shift reaction. • B-site doping leads to nanoparticle exsolution during catalytic reaction. • A-site doping influences surface vacancy concentration for CO 2 activation. • Improved activity due to job-sharing of exsolved nanoparticles and oxide support material. Reverse Water-Gas Shift (rWGS) is among the reactions with the highest readiness level for technological implementation of CO 2 utilization as an abundant and renewable carbon source, and its transformation for instance into synthetic fuels. Hence, great efforts are made in terms of further development and comprehension of novel catalyst materials. To achieve excellent catalytic performance, catalytically active (nano)particles that are evenly distributed on (and ideally embedded in) an active support are crucial. An extremely versatile material class that exhibits the desired properties are perovskite-type oxides due to the fact that they can easily be doped with highly active elements. Upon controlled reduction or during reaction, these dopants leave the perovskite lattice and diffuse through the material to form nanoparticles at the surface (by exsolution) where they can greatly enhance the activity. Here, six perovskites were studied and their exsolution capabilities as well as rWGS performance were explored. Nanoparticle exsolution significantly enhanced the rWGS activity, with the catalytic activity being in the order Nd 0.6 Ca 0.4 Fe 0.9 Co 0.1 O 3- δ > Nd 0.6 Ca 0.4 Fe 0.9 Ni 0.1 O 3- δ > Nd 0.9 Ca 0.1 FeO 3- δ > Nd 0.6 Ca 0.4 FeO 3- δ > La 0.6 Ca 0.4 FeO 3- δ > La 0.9 Ca 0.1 FeO 3- δ > La 0.6 Sr 0.4 FeO 3- δ (benchmark). Moreover, it could be shown that nanoparticles formed due to exsolution are stable at high reaction temperatures. In this paper, the flexibility of the investigated perovskite materials is demonstrated, on the one hand facilitating a material design approach enabling control over size and composition of exsolved nanoparticles. On the other hand, the studied perovskites offer a tuneable host lattice providing oxygen vacancies for efficient CO 2 adsorption, activation, and resulting interface boundaries with the ability to enhance the catalytic activity. [ABSTRACT FROM AUTHOR]

Electron vortex beams were only recently discovered and their potential as a probe for magnetism in materials was shown. Here we demonstrate a method to produce electron vortex beams with a diameter of less than 1.2 Å. This unique way to prepare free electrons to a state resembling atomic orbitals is fascinating from a fundamental physics point of view and opens the road for magnetic mapping with atomic resolution in an electron microscope. [ABSTRACT FROM AUTHOR]

Abstract: Controlled cryopreservation is an important method for storage of tissue grafts in skin banking, reproductive medicine and other domains. Although the availability of cryopreserved flexor tendons would be highly beneficial in reconstructive surgery, especially in complex reconstructions for which grafting material is limited, only a few studies have dealt with transplanted tendons. We achieved successful cryopreservation of porcine flexor tendons in 2 cryoprotective media: dimethyl sulfoxide and glycerol. Their viability was shown using a quantitative colorimetric MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) assay. For comparison of native and cryopreserved tendons (n = 7 samples each), the adopted viability index was the ratio of MTT-dependent optical density and tendon weight. The viability index of native samples did not change significantly after cryopreservation and thawing. The proliferative capacity of tendon fibroblasts after thawing was shown in primary cell cultures. The described cryopreservation protocol and MTT assay may provide a basis for future autografting of human tendons. [Copyright &y& Elsevier]