Toward Operando Structural, Chemical, and Electrochemical Analyses of Solid-State Batteries Using Correlative Secondary Ion Mass Spectrometry Imaging

The global transition from fossil fuels to green energy underpins the need for efficient and reliable energy storage systems. Advanced analysis and characterization of battery materials is not only important to understand fundamental battery properties but also crucial for their continued development. A deep understanding of these systems is often difficult to obtain through only pre- and/or post-mortem analyses, with the full complexity of a battery being hidden in its operational state. Thus, we have developed an operando methodology to analyze solid-state batteries (SSBs) structurally as well as chemically before, during, and after cycling. The approach is based on a specially designed sample holder, which enables a variety of electrochemical experiments. Since the entire workflow is performed within a single focused ion beam scanning electron microscope equipped with an in-house developed magnetic sector secondary ion mass spectrometer, we are able to pause the cycling at any time, perform analysis, and then continue cycling. Microstructural analysis is performed via secondary electron imaging, and the chemical mapping is performed using the secondary ion mass spectrometer. In this proof-of-concept study, we were able to identify dendrites in a short-circuited symmetric cell and to chemically map dendritic structures. While this methodology focuses on SSBs, the approach can directly be adapted to different battery systems and beyond. Our technique clearly has an advantage over many alternatives for battery analysis as no transfer of samples between instruments is needed and a correlation between the microstructure, chemical composition, and electrochemical performance is obtained directly.

Effect of Surface Roughness and Droplet Size on Solder Wetting Angles

Reactive wetting is a process ubiquitous in modern electronic soldering processes. Nonetheless, the dependencies of reactive wetting angles on surface roughness and droplet size are not well understood but become increasingly important for reliable miniaturization of devices. In this study, advancing contact angles of the Sn^(l)/Cu^(s) reactive solder system are investigated and the aforementioned dependencies are evaluated. Several surface roughnesses and a large array of droplet sizes are measured. Clear size dependencies are observed for both smooth and rough substrates, yet interestingly, the trends are inverted. This inversion of the size dependence of the wetting angle is discussed on the basis of the triple line pinning phenomenon, Wenzel's wetting model, and the consumption of Sn by a solder reaction. Quantitative models are proposed, with which size dependencies on rough and smooth surfaces can be better understood. Triple line pinning barrier energies are calculated. Larger pinning barriers are determined for rougher substrates.

Nanoscale analysis of frozen honey by atom probe tomography

Three-dimensional reconstruction of the analysed volume is one of the main goals of atom probe tomography (APT) and can deliver nearly atomic resolution (~ 0.2 nm spatial resolution) and chemical information with a mass sensitivity down to the ppm range. Extending this technique to frozen biological systems would have an enormous impact on the structural analysis of biomolecules. In previous works, we have shown that it is possible to measure frozen liquids with APT. In this paper, we demonstrate the ability of APT to trace nanoscale precipitation in frozen natural honey. While the mass signals of the common sugar fragments C_xH_y and C_xO_yH_z overlap with (H₂O)_nH from water, we achieved correct stoichiometric values via different interpretation approaches for the peaks and thus determined the water content reliably. Next, we use honey to investigate the spatial resolution capabilities as a step toward the measurement of biological molecules in solution in 3D with sub-nanometer resolution. This may take analytical techniques to a new level, since methods of chemical characterization for cryogenic samples, especially biological samples, are still limited.

Understanding the Underlying Field Evaporation Mechanism of Pure Water Tips in High Electrical Fields

We investigated the field evaporation process of frozen water in atom probe tomography (APT) by density functional simulations. In previous experiments, a strong tailing effect was observed for peaks caused by the molecular structure (H₂O)_nH⁺, in contrast to other peaks. In purely field-induced and thermally assisted evaporation simulations, we found that chains of protonated water molecules were pulled out of the dielectric surface by up to 6 Å, which are stable over a wide range of field strengths. Therefore, the resulting water clusters experience only part of the acceleration after evaporation compared to molecules evaporating directly from the surface and, thus, exhibit an energy deficit, which explains the tailing effect. Our simulations provide new insight into the complex evaporation behavior of water in high electrical fields and reveal possibilities for adapting the existing reconstruction algorithms.

Status and Direction of Atom Probe Analysis of Frozen Liquids

Imaging of liquids and cryogenic biological materials by electron microscopy has been recently enabled by innovative approaches for specimen preparation and the fast development of optimized instruments for cryo-enabled electron microscopy (cryo-EM). Yet, cryo-EM typically lacks advanced analytical capabilities, in particular for light elements. With the development of protocols for frozen wet specimen preparation, atom probe tomography (APT) could advantageously complement insights gained by cryo-EM. Here, we report on different approaches that have been recently proposed to enable the analysis of relatively large volumes of frozen liquids from either a flat substrate or the fractured surface of a wire. Both allowed for analyzing water ice layers which are several micrometers thick consisting of pure water, pure heavy water, and aqueous solutions. We discuss the merits of both approaches and prospects for further developments in this area. Preliminary results raise numerous questions, in part concerning the physics underpinning field evaporation. We discuss these aspects and lay out some of the challenges regarding the APT analysis of frozen liquids.

A Modular Atom Probe Concept: Design, Operational Aspects, and Performance of an Integrated APT-FIB/SEM Solution

Atomic probe tomography (APT) is able to generate three-dimensional chemical maps in atomic resolution. The required instruments for APT have evolved over the last 20 years from an experimental to an established method of materials analysis. Here, we describe the realization of a new modular instrument concept that allows the direct attachment of APT to a dual-beam SEM microscope with the main achievement of fast and direct sample transfer and high flexibility in chamber and component configuration. New operational modes are enabled regarding sample geometry, alignment of tips, and the microelectrode. The instrument is optimized to handle cryo-samples at all stages of preparation and storage. It comes with its own software for evaluation and reconstruction. The performance in terms of mass resolution, aperture angle, and detection efficiency is demonstrated with a few application examples.

Quantitative Distinction between Noble Metals Located in Mesopores from Those on the External Surface

We compare three methods for quantitatively distinguishing the location of noble metal (NM) particles in mesopores from those found on the external support surface. MCM‐41 and SBA‐15 with NM located in mesopores or on the external surface were prepared and characterized by TEM. ³¹P MAS NMR spectroscopy was used to quantify arylphosphines in complexes with NM. Phosphine/NM ratios drop from 2.0 to 0.2 when increasing the probe diameter from 1.08 to 1.54 nm. The reaction between NM and triphenylphosphine (TPP) within 3.0 nm MCM‐41 pores takes due to confinement effects multiple weeks. In contrast, external NM react with TPP instantly. A promising method is filling the pores by using the pore volume impregnation technique with tetraethylorthosilicate (TEOS). TPP loading revealed that 66 % of NMs are located on the external surface of MCM‐41. The pore filling method can be used in association with any probe molecule, also for the quantification of acid sites.

Atom Probe Study of the Miscibility Gap in CuNi Thin Films and Microstructure Development

The unclear miscibility of CuNi alloys was investigated with atom probe tomography (APT). Multilayered thin film samples were prepared by ion beam sputtering (IBS) and focused ion beam (FIB) shaping. Long-term isothermal annealing treatments in a UHV furnace were conducted at temperatures of 573, 623, and 673 K to investigate the mixing process. The effective interdiffusion coefficient of the nanocrystalline microstructure (including defect diffusion) was determined to be Deff = 1.86 × 10−10 m2/s × exp(−164 kJ/mol/RT) by fitting periodic composition profiles through a Fourier series. In nonequilibrium states, microstructural defects like grain boundaries and precipitates were observed. While at the two higher temperatures total mixing is observed, a clear experimental evidence is found for a miscibility gap at 573 K with the boundary concentrations of 26 and 66 at%. These two compositions are used in a subregular solution model to reconstruct the phase miscibility gap. So, the critical temperature TC of the miscibility gap is found to be 608 K at a concentration of 45 at% Ni.

Slow-Moving Phase Boundary in Li4/3+ x Ti5/3 O4

Lithium titanate is one of the most promising anode materials for high-power demands but such applications desire a complete understanding of the kinetics of lithium transport. The poor diffusivity of lithium in the completely lithiated and delithiated (pseudo spinel) phases challenges to explain the high-rate performance. This study aims at clearing the kinetics of lithium transport using an innovative technique that employs optical microscopy in a constrained region of sputter-deposited thin-film samples. It enables the in situ observation of the transport of lithium through the electrode. Furthermore, with a thermostatically controlled cell, the Arrhenius-like temperature dependence is revealed. The quantitative findings demonstrate that indeed the end phases have poor diffusivity which is, however, accelerated at intermediate Li concentrations in the spinel structured Li_{4/3+ δ} Ti_5/3 O₄ phase. Surprisingly, the slow migration of the phase boundary hinders the formation of the Li-rich (rock-salt) phase in the initial stages. Such kinetic control by the phase boundary stands in obvious contrast to a prior (theoretical) study postulating almost "liquid" behavior of the interface. Only after the Li diffusion into the Li-poor (spinel) phase has faded, when approaching the solubility limit, the further growth of the rock-salt phase becomes diffusion controlled.

Atom Probe Study of 1-Octadecanethiol Self-Assembled Monolayers on Platinum (111) and (200) Surfaces

Atom probe tomography measurements of self-assembled monolayers of 1-octadecanethiol on platinum tips were performed and their fragmentation behavior under the influence of different laser powers was investigated. The carbon backbone evaporates in the form of small hydrocarbon fragments consisting of one to four carbon atoms, while sulfur evaporates exclusively as single ions. The carbon molecules evaporate at very low fields of 5.9 V/nm, while S requires a considerably higher evaporation field of 23.4 V/nm. With increasing laser power, a weak, but noticeable trend toward larger fragment sizes is observed. No hydrocarbon fragments containing S are detected, indicating that a strong S–Pt bond has formed. The observed surface coverage of S fits well with literature values and is higher for (111)-oriented samples than for (200).

3D sub-nanometer analysis of glucose in an aqueous solution by cryo-atom probe tomography

Atom Probe Tomography (APT) is currently a well-established technique to analyse the composition of solid materials including metals, semiconductors and ceramics with up to near-atomic resolution. Using an aqueous glucose solution, we now extended the technique to frozen solutions. While the mass signals of the common glucose fragments C_xH_y and C_xO_yH_z overlap with (H₂O)_nH from water, we achieved stoichiometrically correct values via signal deconvolution. Density functional theory (DFT) calculations were performed to investigate the stability of the detected pyranose fragments. This paper demonstrates APT’s capabilities to achieve sub-nanometre resolution in tracing whole glucose molecules in a frozen solution by using cryogenic workflows. We use a solution of defined concentration to investigate the chemical resolution capabilities as a step toward the measurement of biological molecules. Due to the evaporation of nearly intact glucose molecules, their position within the measured 3D volume of the solution can be determined with sub-nanometre resolution. Our analyses take analytical techniques to a new level, since chemical characterization methods for cryogenically-frozen solutions or biological materials are limited.

Elastic Behavior of Nb2O5/Al2O3 Core-Shell Nanowires in Terms of Short-Range-Order Structures

Single-crystalline niobium pentoxide nanowires (NWs) of length 10-15 μm and diameter 100-200 nm are synthesized by thermal oxidation of niobium substrates in a mild vacuum (3-10 mbar). Amorphous Al₂O₃ shells of varying thicknesses (10, 30, 40, and 50 nm) are deposited on top of the wires using atomic layer deposition. Bending tests of the uncoated Nb₂O₅ NWs and the Nb₂O₅/Al₂O₃ core-shell NWs are carried out inside a scanning electron microscope using a micromanipulator with a force measurement tip. The experimental deflection curves are modeled with Euler-Bernoulli (E-B) beam theory, and the Young's modulus is manipulated to determine the best fit. The Nb₂O₅ NWs with no shell are determined to have a Young's modulus of 67 ± 10 GPa, which agrees with the published data on Nb₂O₅ thin films. For core-shell NWs, only small deflections of the wires with 10 and 30 nm thick shells can be fitted with the E-B model when utilizing constant Young's modulus values of 67 GPa for the Nb₂O₅ core and about 160 GPa for the Al₂O₃ shell. When allowing for a change in the Young's modulus of the Al₂O₃ shell, the Young's modulus is determined to be at 120 ± 10 GPa for 10 nm and 145 ± 12 GPa for 30 nm at the highest applied load. For thicknesses of 40 nm and 50 nm, we observed a reduced but constant 120 ± 11 and 111 ± 10 GPa, respectively. Such behavior may result from structural disordering of the amorphous Al₂O₃ through reducing fractions of the densely packed polyhedra, while the fractions of the loosely packed polyhedra increase as a result of the increasing strain or the fabrication process. The increased disorder is associated with increased average interatomic spacing. Thus, the atomic bonding force and also the Young's modulus decrease.

Optimizing the plasma oxidation of aluminum gate electrodes for ultrathin gate oxides in organic transistors

A critical requirement for the application of organic thin-film transistors (TFTs) in mobile or wearable applications is low-voltage operation, which can be achieved by employing ultrathin, high-capacitance gate dielectrics. One option is a hybrid dielectric composed of a thin film of aluminum oxide and a molecular self-assembled monolayer in which the aluminum oxide is formed by exposure of the surface of the aluminum gate electrode to a radio-frequency-generated oxygen plasma. This work investigates how the properties of such dielectrics are affected by the plasma power and the duration of the plasma exposure. For various combinations of plasma power and duration, the thickness and the capacitance of the dielectrics, the leakage-current density through the dielectrics, and the current-voltage characteristics of organic TFTs in which these dielectrics serve as the gate insulator have been evaluated. The influence of the plasma parameters on the surface properties of the dielectrics, the thin-film morphology of the vacuum-deposited organic-semiconductor films, and the resulting TFT characteristics has also been investigated.

Compensating Local Magnifications in Atom Probe Tomography for Accurate Analysis of Nano-Sized Precipitates

Local magnification artifacts in atom probe tomography (APT) caused by multiphase materials with heterogeneous evaporation behavior are a well-known problem. In particular, the analysis of the exact size, shape, and composition of small precipitates is, therefore, not trivial. We performed numerical simulations of APT measurements to predict the reconstructed morphology of precipitates with contrasting evaporation thresholds. Based on a statistical approach that avoids coarse graining, the simulated data are evaluated to develop a model for the calculation of the original size of the precipitates. The model is tested on experimental APT data of precipitates with a higher and lower evaporation field in a ferritic alloy. Accurate sizes, proven by a complementary investigation by transmission electron microscopy, are obtained. We show further, how the size information can be used to obtain compositional information of the smallest precipitates and present a new methodology to determine a correct in-depth scaling of the APT reconstruction in case no complementary geometric information about the specimen exists or if no lattice planes are visible in the reconstruction.

Field evaporation and atom probe tomography of pure water tips

Measuring biological samples by atom probe tomography (APT) in their natural environment, i.e. aqueous solution, would take this analytical method, which is currently well established for metals, semi-conductive materials and non-metals, to a new level. It would give information about the 3D chemical structure of biological systems, which could enable unprecedented insights into biological systems and processes, such as virus protein interactions. For this future aim, we present as a first essential step the APT analysis of pure water (Milli-Q) which is the main component of biological systems. After Cryo-preparation, nanometric water tips are field evaporated with assistance by short laser pulses. The obtained data sets of several tens of millions of atoms reveal a complex evaporation behavior. Understanding the field evaporation process of water is fundamental for the measurement of more complex biological systems. For the identification of the individual signals in the mass spectrum, DFT calculations were performed to prove the stability of the detected molecules.

Evaporation and Fragmentation of Organic Molecules in Strong Electric Fields Simulated with DFT

Atom probe tomography allows us to measure the three-dimensional composition of materials with up to atomic resolution by evaporating the material using high electric fields. Initially developed for metals, it is increasingly used for covalently bound structures. To aid the interpretation of the obtained fragmentation pattern, we modeled the fragmentation and desorption of self-assembled monolayers of thiolate molecules on a gold surface in strong electrostatic fields using density functional theory. We used a cluster model and a periodic model of amino-undecanethiolate, NH₂(CH₂)₁₁S, and fluoro-decanethiolate, CF₃(CF₂)₇(CH₂)₂S. In the former molecule, the fragment CH₂NH₂⁺ was found to evaporate at fields of 5.4-7.7 V/nm. It was followed by different hydrocarbon fragments. Fluoro-decanethiolate evaporates CF₃⁺ at fields of 5.7-6.7 V/nm in the cluster model and at 15.4-23.1 V/nm in the periodic model, followed by CF₂⁺ and C₂F₄²⁺. Detailed analysis of the electronic structure during the evaporation process revealed a stepwise accumulation of the charge in the head groups exposed to the strongest fields, followed by dissociation of covalent bonds. These observations will facilitate the analysis of atom probe experiments of covalently bound structures.

Beyond linearity: bent crystalline copper nanowires in the small-to-moderate regime

Several models can describe the nonlinear response of 1D objects to bending under a concentrated load. Successive stages consisting of geometrical and, additionally, mechanical non-linearity can be identified in moderately large extensions. We provide an explicit bending moment function with terms accounting for the linearity (Euler-Bernoulli), quasi-linearity, geometrical and finally, mechanical non-linearity as global features of a moderately large elastic deformation. We apply our method, also suitable for other metals, to the experimental data of Cu nanowires (NWs) with an aspect ratio of about 16 under different concentrated loadings. The spatial distribution of strain-hardening/softening along the wire or through the cross-section is also demonstrated. As a constitutive parameter, the strain-dependent stretch modulus represents, undoubtedly, changes in the material properties as the deformation progresses. At the highest load, the Green-Lagrange strain reaches a 12.5% extension with a corresponding ultra-high strength of about 7.45 GPa at the most strained volume still in the elastic regime. The determined stretch modulus indicates a significantly lower elastic response with an approximated Young's modulus (E ≅ 65 GPa) and a third-order elastic constant, C ₁₁₁ ≅ -350 GPa. Surprisingly, these constants suggest a 25-35% of that of the bulk counterparts. Ultimately, the method not only provides a quantitative description of the bent Cu NWs, but also indicates the robustness of the theory of nonlinear elasticity.

Structural phase transformations in annealed Pt/Mn/Fe trilayers

Thermally-activated phase transitions in Pt/Mn/Fe thin films were investigated by a combination of x-ray diffraction, transmission electron microscopy, secondary neutral mass spectrometry depth profiling, atomic force microscopy, and magnetic properties measurements. Post-annealing was carried out in vacuum to different temperatures up to 620 °C. Initially, at temperatures between 280 °C-450 °C first L10-MnPt is formed at the Mn/Pt interface followed by the most likely formation of metastable bcc Fe3Pt, which gets transformed by further annealing to fcc Fe3Pt and eventually to chemically ordered L12-Fe3Pt. The final product after annealing at 620 °C consists of two interesting phases, which are relevant for spintronic applications, antiferromagnetic L10-MnPt with addition of Fe and ferromagnetic L12-Fe3Pt, consistent with the initial element composition.

Electrochromic Behavior and Phase Transformation in Li4+xTi5O12 upon Lithium-Ion Deintercalation/Intercalation

The impact of phase transformation from spinel-structured Li₄Ti₅O₁₂ to rocksalt-type Li₇Ti₅O₁₂ on the electrochromic properties of the material is studied. Thin films of Li₄Ti₅O₁₂ are deposited on platinum-coated substrates using radio-frequency-ion beam sputtering. In situ and ex situ optical spectroscopy (in reflectance geometry) is performed along with electrochemical characterization. In situ measurements demonstrate the reversible electrochromic behavior of the deposited thin films and the effect of the change of lithium content on the reflectance spectrum. Ex situ measurements quantify the optical constants of thin films for different charge states by modeling the reflectance spectrum with a Clausius-Mossotti relation. The model reveals the presence of one or two dominant resonant frequencies in the case of Li₄Ti₅O₁₂ or Li₇Ti₅O₁₂, respectively, in the UV/visible/NIR region of light. The single strong resonance in the case of Li₄Ti₅O₁₂ is assigned to transition from O 2p to Ti t_2g, that is, across the band gap, whereas for the Li₇Ti₅O₁₂ phase, the two resonances correspond to the electronic transitions from O 2p to empty Ti t_2g and from filled Ti t_2g to empty Ti e_g. The concentration dependence of the derived dielectric constants points out a fast lithium ion transport through the grain boundaries, thereby segregating a conductive lithium-rich phase at the grain boundaries. This increases the electronic conductivity of the thin films in the initial stages of intercalation and explains the debated mechanism of the fast discharge/charge capability of Li₄Ti₅O₁₂ electrodes.

Miniaturization, Triple-Line Effects, and Reactive Wetting of Microsolder Interfaces

While reactive microsolder joints are of ubiquitous importance in modern electronics, the effects of joint miniaturization on wetting behavior remain largely unexplored. We elucidate this fundamental question of scalability by investigating the wettability of eutectic SnPb solder on Cu and Ni-electrodeposited metallization strips of varying widths. Contact angles are presented in dependence of the metallization width which is varied from 3 mm down to ∼100 μm. The measured angles clearly increase with decreasing metallization width. Based on the measurements and by modifying Young's equation, it is shown that the behavior of the wetting angle can be quantitatively understood with an "effective" triple-line energy of ϵ_t = (753 ± 31) × 10^-9J/m for SnPb on Cu. The interpretation of this energy term is discussed in relation to the forming intermetallic phase and the ensuing surface roughness. A remarkable similarity between the experimentally observed size dependence and the crossed-groove perturbation model of Huh and Mason demonstrates that the rough intermetallic phase induces wetting hysteresis such that it is quantitatively well described by an effective triple-line energy.

Extracting the shape of nanometric field emitters

The high resolution nanoanalysis by atom probe tomography is based on needle-shaped samples that represent nanometric field emitters with typical curvature radii of 50 nm. After field desorption and detection of a large set of atoms, the sample volume has to be numerically reconstructed. Conventionally, this reconstruction is performed with the assumption of a hemispherical apex. This established practice can lead to serious distortions of the tomography. In this work, we demonstrate how the real shape of the emitter can be extracted from the event density on the 2D detector setup. Except for convexity, no other restriction is imposed on the shape. The required mathematics is derived and the method is demonstrated with numerically simulated and experimental data sets of complex tip shapes. The computational effort of the method is also suitable to handle data sets of a few hundred million atoms.

High capacity rock salt type Li2MnO3-δ thin film battery electrodes

Recent investigations of layered, rock salt and spinel-type manganese oxides in composite powder electrodes revealed the mutual stabilization of the Li–Mn–O compounds during electrochemical cycling. A novel approach of depositing such complex compounds as an active cathode material in thin-film battery electrodes is demonstrated in this work. It shows the maximum capacity of 226 mA h g⁻¹ which is superior in comparison to that of commercial LiMn₂O₄ powder as well as thin films. Reactive ion beam sputtering is used to deposit films of a Li₂MnO_3−δ composition. The method allows for tailoring of the active layer's crystal structure by controlling the oxygen partial pressure during deposition. Electron diffractometry reveals the presence of layered monoclinic and defect rock salt structures, the former transforms during cycling and results in thin films with extraordinary electrochemical properties. X-ray photoelectron spectroscopy shows that a large amount of disorder on the cation sub-lattices has been incorporated in the structure, which is beneficial for lithium migration and cycle stability.

The work demonstrates a novel route to synthesize disorder rich rock salt-type Li₂MnO_3−δ electrodes flaunting remarkably high capacity due to dynamic phase transformation during cycling.

Synthesis and thermal reaction of stainless steel nanowires

Due to the perfection of microelectronics fabrication, silicon is presently the preferred base material in the design of micromechanical devices. By contrast, steels are the dominating construction materials in macroscopic engineering. So, it is appealing to explore the potential of stainless steel nano objects. To this aim, we developed an electrochemical method for and investigated the fabrication of FeCr(C) nanowires and study their thermal reaction to design the microstructure. Wires, 50 to 150 nm in diameter, are produced by template-assisted electro-deposition. Under thermal annealing, they develop first a core-shell structure of an Fe-rich core and a dense Cr-rich carbide shell. The shell thickness is well controllable via the initial composition of the wires. In a later, second reaction stage, wires with rather thin shells (about 8 nm thickness) demonstrate a 'stacking inversion' that finally leads in a self-driven reaction to the formation of hollow carbide tubes decorated with iron rich clusters on their outer surface.

Arabidopsis species deploy distinct strategies to cope with drought stress

BACKGROUND AND AIMS

Water limitation is an important determinant of the distribution, abundance and diversity of plant species. Yet, little is known about how the response to limiting water supply changes among closely related plant species with distinct ecological preferences. Comparison of the model annual species Arabidopsis thaliana with its close perennial relatives A. lyrata and A. halleri, can help disentangle the molecular and physiological changes contributing to tolerance and avoidance mechanisms, because these species must maintain tolerance and avoidance mechanisms to increase long-term survival, but they are exposed to different levels of water stress and competition in their natural habitat.

METHODS

A dry-down experiment was conducted to mimic a period of missing precipitation. The covariation of a progressive decrease in soil water content (SWC) with various physiological and morphological plant traits across a set of representative genotypes in A. thaliana, A. lyrata and A. halleri was quantified. Transcriptome changes to soil dry-down were further monitored.

KEY RESULTS

The analysis of trait covariation demonstrates that the three species differ in the strategies they deploy to respond to drought stress. Arabidopsis thaliana showed a drought avoidance reaction but failed to survive wilting. Arabidopsis lyrata efficiently combined avoidance and tolerance mechanisms. In contrast, A. halleri showed some degree of tolerance to wilting but it did not seem to protect itself from the stress imposed by drought. Transcriptome data collected just before plant wilting and after recovery corroborated the phenotypic analysis, with A. lyrata and A. halleri showing a stronger activation of recovery- and stress-related genes, respectively.

CONCLUSIONS

The response of the three Arabidopsis species to soil dry-down reveals that they have evolved distinct strategies to face drought stress. These strategic differences are in agreement with the distinct ecological priorities of the stress-tolerant A. lyrata, the competitive A. halleri and the ruderal A. thaliana.

Achieving Ultralow Turn-On Voltages in Organic Thin-Film Transistors: Investigating Fluoroalkylphosphonic Acid Self-Assembled Monolayer Hybrid Dielectrics

The properties of organic thin-film transistors (TFTs) and thus their ability to address specific circuit design requirements depend greatly on the choice of the materials, particularly the organic semiconductor and the gate dielectric. For a particular organic semiconductor, the TFT performance must be reviewed for different combinations of substrates, fabrication conditions, and the choice of the gate dielectric in order to achieve the optimum TFT and circuit characteristics. We have fabricated and characterized organic TFTs based on the small-molecule organic semiconductor 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene in combination with an ultrathin hybrid gate dielectric consisting of aluminum oxide and a self-assembled monolayer. Fluoroalkylphosphonic acids with chain lengths ranging from 6 to 14 carbon atoms have been used to form the self-assembled monolayer in the gate dielectric, and their influence on the TFT characteristics has been studied. By optimizing the fabrication conditions, a turn-on voltage of 0 V with an on/off current ratio above 10⁶ has been achieved, in combination with charge-carrier mobilities up to 0.4 cm²/V s on flexible plastic substrates and 1 cm²/V s on silicon substrates.

Atom Probe Reconstruction With a Locally Varying Emitter Shape

An improved reconstruction method for atom probe tomography is presented. In this approach, the curvature of the field emitter is variable, in contrast to the conventional reconstruction technique. The information about the tip shape at different stages of the reconstruction is directly extracted from the local density of events on the detector. To this end, the detector and the tip surface are split into different segments. According to the density distribution of events observed on the detector, the size of the corresponding segment on the tip surface is calculated, yielding an emitter profile which is not necessarily spherical. The new approach is demonstrated for emitter structures with radial symmetry that contain a spherical precipitate with a substantially lower or higher evaporation field compared to the surrounding matrix. A comparison to the conventional point projection approach is made.

Ionic conductivity of melt-frozen LiBH4 films

The fast Li conductivity of LiBH₄ envisages its use in all-solid-state batteries. Powders are commonly applied. But here, we study the formation of dense micrometer films by melting, spinning and subsequent solidifying. Characterized by electron microscopy, and spectroscopy (EDX/XPS/impedance), a reversible phase transformation is confirmed as well as a maximum conductivity of 10³ S cm⁻¹.

LiBH₄ melt-frozen film as solid state electrolyte.

Plasma fatty acid profile as biomarker of coronary artery disease: a pilot study using fourth generation artificial neural networks

Many studies, focused on identifying new biomarkers for coronary artery disease (CAD) risk computation and monitoring, suggested a potential diagnostic role for fatty acids (FA). In the present study, we explored the potential diagnostic role of FA by using a data mining approach based on fourth generation artificial neural networks (ANN). Forty-one male subjects were enrolled. According to coronary angiography, 31 displayed CAD and 10 did not (non-CAD, control group). FA analysis was performed on plasma samples using a gas chromatography-mass spectrometry system and analyses were performed by an ANN method. The variables most closely related to CAD were low levels of alpha-linolenic acid, eicosapentaenoic acid, eicosatetraenoic and docosahexaenoic acids. High levels of 1,1-dimethoxyhexadecane, total dimethyl acetals and docosatetraenoic acid were related to non-CAD condition. This subset of variables, which were most closely correlated to the target diagnosis, achieved a consistent predictive rate. The average accuracy obtained was 76.5%, with 93% of sensitivity and 60% of specificity. The area under the ROC curve was equal to 0.79. In conclusion, our study highlighted the association between different plasma FA species, CAD and non-CAD conditions. The specific subset of variables could be of interest as a new diagnostic tool for CAD management.

Expression of the sodium iodide symporter in differentiated thyroid cancer

Aim: Molecular analysis of the expression of the sodium iodide symporter (NIS) in 32 patients with differentiated thyroid cancer (DTC) and correlation with scintigraphic findings (131I,123I) in 19 (59.4%) of them. Patients, methods: NIS expression of 27 primary tumours, 13 lymphnodes and 18 distant metastases was determined by immunostaining using a murine monoclonal anti-NIS-antibody. NIS expression and radionuclide uptake of metastases were analysed by a semiquantitative visual score. Patients were divided into two subgroups: Group 1 (n = 8 patients): indirect correlation of radioiodine uptake (RIU) of subsequent metastases with NIS expression of 7 primary tumours and 3 metastases; Group 2 (n=11 patients): direct correlation of radionuclide uptake with NIS expression of 19 metastases which were excised after imaging. Results: 49 of 58 specimens (84.5%) were NIS-positive. A preserved NIS-expression was found in 12 primary tumours and 8 of 10 (80%) synchrone and 6 of 7 (85.7%) metachrone metastases. Group 1 revealed a 100% positive predictive value (PPV) of a preserved NIS expression in the primary tumour regarding radioiodine uptake in metastases while a lack of NIS expression in the primary tumor did not reliable predict a loss of the metastases’ ability to concentrate radioiodine. In group 2, only 11 of 19 (57.9%) specimens showed a concordant NIS expression and RIU whereas in the remaining 8 cases without visible RIU NIS expression was still present. Conclusions: NIS expression of the primary tumour and metastases in DTC is usually well preserved. We found a positive correlation between NIS expression of the primary and metastatic tissue but could not identify such well correspondence between NIS expression and the RIU of subsequent metastases.

Mildly oxidized HDL decrease agonist-induced platelet aggregation and release of pro-coagulant platelet extracellular vesicles

Stored platelet concentrates (PLCs) for therapeutic purpose, develop a platelet storage lesion (PSL), characterized by impaired platelet (PLT) viability and function, platelet extracellular vesicle (PL-EV) release and profound lipidomic changes. Whereas oxidized low-density lipoprotein (oxLDL) activates PLTs and promotes atherosclerosis, effects linked to oxidized high-density lipoprotein (oxHDL) are poorly characterized. PLCs from blood donors were treated with native (nHDL) or mildly oxidized HDL (moxHDL) for 5days under blood banking conditions. Flow cytometry, nanoparticle tracking analysis (NTA), aggregometry, immunoblot analysis and mass spectrometry were carried out to analyze PL-EV and platelet exosomes (PL-EX) release, PLT aggregation, protein expression, and PLT and plasma lipid composition. In comparison to total nHDL, moxHDL significantly decreased PL-EV release by -36% after 5days of PLT storage and partially reversed agonist-induced PLT aggregation. PL-EV release positively correlated with PLT aggregation. MoxHDL improved PLT membrane lipid homeostasis through enhanced uptake of lysophospholipids and their remodeling to corresponding phospholipid species. This also appeared for sphingomyelin (SM) and d18:0/d18:1 sphingosine-1-phosphate (S1P) at the expense of ceramide (Cer) and hexosylceramide (HexCer) leading to reduced Cer/S1P ratio as PLT-viability indicator. This membrane remodeling was associated with increased content of CD36 and maturation of scavenger receptor-B1 (SR-B1) protein in secreted PL-EVs. MoxHDL, more potently than nHDL, improves PLT-membrane lipid homeostasis, partially antagonizes PL-EV release and agonist-induced PLT aggregation. Altogether, this may be the result of more efficient phospho- and sphingolipid remodeling mediated by CD36 and SR-B1 in the absence of ABCA1 on PLTs. As in vitro supplement in PLCs, moxHDL has the potential to improve PLC quality and to prolong storage.

Comparative lipidomic analysis of synovial fluid in human and canine osteoarthritis

OBJECTIVE

The lipid profile of synovial fluid (SF) is related to the health status of joints. The early stages of human osteoarthritis (OA) are poorly understood, which larger animals are expected to be able to model closely. This study examined whether the canine groove model of OA represents early OA in humans based on the changes in the lipid species profile in SF. Furthermore, the SF lipidomes of humans and dogs were compared to determine how closely canine lipid species profiles reflect the human lipidome.

METHODS

Lipids were extracted from cell- and cellular debris-free knee SF from nine donors with healthy joints, 17 patients with early and 13 patients with late osteoarthritic changes, and nine dogs with knee OA and healthy contralateral joints. Lipid species were quantified by electrospray ionization tandem mass spectrometry (ESI-MS/MS).

RESULTS

Compared with control canine SF most lipid species were elevated in canine OA SF. Moreover, the lipid species profiles in the canine OA model resembled early OA profiles in humans. The SF lipidomes between dog and human were generally similar, with differences in certain lipid species in the phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) classes.

CONCLUSIONS

Our lipidomic analysis demonstrates that SF in the canine OA model closely mimics the early osteoarthritic changes that occur in humans. Further, the canine SF lipidome often reflects normal human lipid metabolism.

Epicardial adipocyte hypertrophy: Association with M1-polarization and toll-like receptor pathways in coronary artery disease patients

BACKGROUND AND AIMS

In coronary artery disease (CAD) epicardial adipose tissue (EAT) shows an elevated inflammatory infiltrate. Toll-like receptors (TLRs) are important mediators of adipose tissue inflammation and they are able to recognize endogenous products released by damaged cells. Because adipocyte death may be driven by hypertrophy, our aim was to investigate in CAD and non-CAD patients the association between EAT adipocyte size, macrophage infiltration/polarization and TLR-2 and TLR-4 expression.

METHODS AND RESULTS

EAT biopsies were collected from CAD and non-CAD patients. The adipocyte size was determined by morphometric analysis. Microarray technology was used for gene expression analysis; macrophage phenotype and TLRs expression were analyzed by immunofluorescence and immunohistochemical techniques. Inflammatory mediator levels were determined by immunoassays. EAT adipocytes were larger in CAD than non-CAD patients and do not express perilipin A, a marker of lipid droplet integrity. In CAD, EAT is more infiltrated by CD68-positive cells which are polarized toward an M1 state (CD11c positive) and presents an increased pro-inflammatory profile. Both TLR-2 and TLR-4 expression is higher in EAT from CAD and observed on all the CD68-positive cells.

CONCLUSIONS

Our findings suggested that EAT hypertrophy in CAD promotes adipocyte degeneration and drives local inflammation through increased infiltration of macrophages which are mainly polarized towards an M1 state and express both TLR-2 and TLR-4.

Epicardial adipose tissue inflammation is related to vitamin D deficiency in patients affected by coronary artery disease

BACKGROUND AND AIMS

Alterations in epicardial adipose tissue (EAT) biology (i.e. increased fat thickness and inflammation) have been described in coronary artery disease (CAD) patients. In addition to its classic role in the regulation of calcium-phosphate homeostasis, vitamin D may exert immune-regulatory and anti-inflammatory effects. Whether EAT inflammation may be linked to vitamin D deficiency is still unknown. In the present study we evaluated plasma 25-hydroxycholecalciferol (25OHD) level in CAD patients and its relationship with EAT ability to locally metabolize vitamin D, EAT expression of inflammation-related molecules and EAT thickness.

METHODS AND RESULTS

Plasma 25OHD level was quantified by an immunoluminometric assay. EAT expression of inflammation-related molecules (MCP-1, PTX3, TNFα, IL-6, adiponectin), vitamin D receptor (VDR), CYP27B1 (25OHD-activating enzyme) and CYP24A1 (1,25-dihydroxycholecalciferol-metabolizing enzyme) was performed by microarray. EAT thickness was quantified by echocardiography. Median plasma 25OHD level was 10.85 ng/mL and 83% of CAD patients displayed 25OHD level below 20 ng/mL. At decreasing plasma 25OHD concentration, we observed a down-regulation in CYP27B1 and CYP24A1 level and an increased expression of VDR and pro-inflammatory cytokines (MCP-1, PTX3, TNFα, IL-6) at EAT level. No correlation was observed between plasma 25OHD level and EAT thickness.

CONCLUSION

Our data suggest an increased activation of inflammatory pathways at EAT level possibly related to systemic and local vitamin D deficiency in CAD patients. Whether maintaining an optimal vitamin D status may be helpful to reduce EAT inflammation and to prevent CAD and its progression needs further investigation.

Ultrastructure of skin from Refsum disease with emphasis on epidermal lamellar bodies and stratum corneum barrier lipid organization

Classic Refsum disease (RD) is a rare, autosomal recessively-inherited disorder of peroxisome metabolism due to a defect in the initial step in the alpha oxidation of phytanic acid (PA), a C16 saturated fatty acid with four methyl side groups, which accumulates in plasma and lipid enriched tissues (please see van den Brink and Wanders, Cell Mol Life Sci 63:1752-1765, 2006). It has been proposed that the disease complex in RD is in part due to the high affinity of phytanic acid for retinoid X receptors and peroxisome proliferator-activated receptors. Structurally, epidermal hyperplasia, increased numbers of cornified cell layers, presence of cells with lipid droplets in stratum basale and reduction of granular layer to a single layer have been reported by Blanchet-Bardon et al. (The ichthyoses, SP Medical & Scientific Books, New York, pp 65-69, 1978). However, lamellar body (LB) density and secretion were reportedly normal. We recently examined biopsies from four unrelated patients, using both OsO4 and RuO4 post-fixation to evaluate the barrier lipid structural organization. Although lamellar body density appeared normal, individual organelles often had distorted shape, or had non-lamellar domains interspersed with lamellar structures. Some of the organelles seemed to lack lamellar contents altogether, showing instead uniformly electron-dense contents. In addition, we also observed mitochondrial abnormalities in the nucleated epidermis. Stratum granulosum-stratum corneum junctions also showed co-existence of non-lamellar and lamellar domains, indicative of lipid phase separation. Also, partial detachment or complete absence of corneocyte lipid envelopes (CLE) was seen in the stratum corneum of all RD patients. In conclusion, abnormal LB contents, resulting in defective lamellar bilayers, as well as reduced CLEs, likely lead to impaired barrier function in RD.

Spinodal Decomposition in a Polystyren/ Cyclohexane Solution of Critical Composition

Results of experiments are reported demonstrating spinoidal decomposition in a critical mixture of polystyrene and cyclohexane. If time and length are properly scaled using data obtained from static and dynamic light scattering exper­ iments, the time evolution of the “spinodal ring” is repre­sented to a good approximation by an empirical equation proposed by Snyder and Meakin which describes spinodal decomposition for various types of systems.

Neonatal respiratory insufficiency caused by an (homozygous) ABCA3-stop mutation: a systematic evaluation of therapeutic options

BACKGROUND

Autosomal recessive ABCA3 (ATP-binding cassette protein A3) gene mutations have been associated with neonatal respiratory distress and pediatric interstitial lung disease. The clinical course of the disease depends on the underlying mutations. Therefore, knowledge of course, symptoms and treatment of the disease is important.

PATIENT AND METHODS

A term newborn suffered from progressive respiratory insufficiency, which led to death at the age of 4.8 months. The girl developed interstitial lung disease. Infections as well as structural and functional disorders of the lung were systematically excluded. A homozygous c.4681C > T (Arg 1561 Stop) mutation of the ABCA3 gene was identified. A literature review of the pathophysiology and treatment options of the disease was done. Therapeutic approaches with corticosteroids, macrolide, and hydroxychloroquine did not improve the clinical course.

RESULTS

Therapeutic strategies for chronic interstitial lung disease have been used successfully in cases of a mild clinical course in juvenile patients with ABCA3 gene mutation. In our patient with homozygous ABCA3 gene mutation,they were not effective. Lung transplantation remains as a therapeutic option, but because of donor organ shortage and associated morbidity and mortality it is rarely feasible.

CONCLUSION

More experience in the treatment of newborns with ABCA3 gene mutations is needed. Randomized, prospective evaluation of the different therapeutic approaches in a specific registry may improve prognosis and treatment of affected individuals.