Nano‐Structural Observation of in situ Silica in Natural Rubber Matrix by Three Dimensional Transmission Electron Microscopy

Summary: Three dimensional (3D) nanostructures of particulate silicas in natural rubber (NR) were observed for the first time by use of 3D transmission electron microscopy (3D‐TEM) combined with electron tomography. The method enabled us to visualize and evaluate structural characteristics in 3D space, such as the size and the volume of in situ silica generated in the NR matrix by the sol‐gel reaction of tetraethoxysilane, at nanometer scale resolution.

The reconstructed mass density view of the silica in an in situ silica‐filled natural rubber vulcanizate, as determined by 3D‐TEM.     

基于THz-TDS的陶瓷纤维复合材料缺陷检测分析

新型陶瓷纤维复合材料由短切氧化硅纤维及其胶合物经高温烧结得到的一种轻质多孔材料,材料微观结构特性直接影响着宏观结构特性和功能特性.该类材料的孔隙度分布在84％ ～95％ 之间,微观孔径主要集中在100μm范围内,偶尔有少量纳米孔.陶瓷纤维复合材料以其耐高温、低密度、高比强和抗烧蚀等优异性能在超高声速飞行器外层隔热部件得...     

Real-Time Reconstruction of Arbitrary Slices for Quantitative and In Situ 3D Characterization of Nanoparticles

A detailed 3D investigation of nanoparticles at a local scale is of great importance to connect their structure and composition to their properties. Electron tomography has therefore become an important tool for the 3D characterization of nanomaterials. 3D investigations typically comprise multiple steps, including acquisition, reconstruction, and analysis/quantification. Usually, the latter two steps are performed offline, at a dedicated workstation. This sequential workflow prevents on-the-fly control of experimental parameters to improve the quality of the 3D reconstruction, to select a relevant nanoparticle for further characterization, or to steer an in situ tomography experiment. Here, an efficient approach to overcome these limitations is presented, based on the real-time reconstruction of arbitrary 2D reconstructed slices through a 3D object. Implementation of this method may lead to generalized implementation of electron tomography for routine nanoparticle characterization in 3D.     

Probability Representation of Quantum States

The review of new formulation of conventional quantum mechanics where the quantum states are identified with probability distributions is presented. The invertible map of density operators and wave functions onto the probability distributions describing the quantum states in quantum mechanics is constructed both for systems with continuous variables and systems with discrete variables by using the Born’s rule and recently suggested method of dequantizer–quantizer operators. Examples of discussed probability representations of qubits (spin-1/2, two-level atoms), harmonic oscillator and free particle are studied in detail. Schrödinger and von Neumann equations, as well as equations for the evolution of open systems, are written in the form of linear classical–like equations for the probability distributions determining the quantum system states. Relations to phase–space representation of quantum states (Wigner functions) with quantum tomography and classical mechanics are elucidated.     

Light-Activated Protein Conjugation and 89Zr-Radiolabelling with Water-Soluble Desferrioxamine Derivatives

Protein-conjugates are vital tools in biomedical research, drug discovery and imaging science. For example, functionalised monoclonal antibodies (mAbs) coupled to the desferrioxamine B (DFO) chelate and radiolabelled with ⁸⁹Zr⁴⁺ ions are used as radiopharmaceuticals for diagnostic positron emission tomography (PET). In this context, protein functionalisation requires the formation of a covalent bond that must be achieved without compromising the biological properties of the mAb. Photochemistry offers new synthetic routes toward protein conjugates like ⁸⁹Zr-mAbs but to harness the potential of light-induced conjugation reactions new photoactivatable reagents are required. Herein, we introduce two photoactivatable DFO-derivatives functionalised with an aryl azide (ArN₃) for use in light-activated conjugation and radiosynthesis of ⁸⁹Zr-mAbs. Incorporation of a tris-polyethylene glycol (PEG)₃ linker between DFO and the ArN₃ group furnished water-soluble chelates that were used in the one-pot, photoradiosynthesis of different ⁸⁹Zr-radiolabelled protein conjugates with radiochemical yields up to 72.9±1.9 %. Notably, the DFO-PEG₃ chelates can be readily synthesised in accordance with Good Laboratory Practice (GLP), which will facilitate clinical trials with photoradiolabelled ⁸⁹Zr-mAbs.     

Establishing Radiolanthanum Chemistry for Targeted Nuclear Medicine Applications

We report the first targeted nuclear medicine application of the lanthanum radionuclides ^132/135La. These isotopes represent a matched pair for diagnosis via the positron emissions of ¹³²La and therapy mediated by the Auger electron emissions of ¹³⁵La. We identify two effective chelators, known as DO3Apic and macropa, for these radionuclides. The 18-membered macrocycle, macropa, bound ^132/135La with better molar activity than DO3Apic under similar conditions. These chelators were conjugated to the prostate-specific membrane antigen (PSMA)-targeting agent DUPA to assess the use of radiolanthanum for in vivo imaging. The ^132/135La-labeled targeted constructs showed high uptake in tumor xenografts expressing PSMA. This study validates the use of these radioactive lanthanum isotopes for imaging applications and motivates future work to assess the therapeutic effects of the Auger electron emissions of ¹³⁵La.     

Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis

Commonly used methods to assess crystallinity, micro-/mesoporosity, Brønsted acid site density and distribution (in micro- vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two-dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro- and mesoporosity, and micropore reaction rates.     

A Macroscopically Relevant 3D‐Metrology Approach for Nanocatalysis Research

A 3D nanometrological approach, which considers as an unbiased validation criterion the quantitative match between values of properties determined by macroscopic characterization techniques and those determined from the nanoscopic results, is developed to unveil the details of complex nanocatalysts. This approach takes into account both the peculiar characteristics of this type of materials and the large influence of noise in the tilt series. It combines, in an optimized way, the latest experimental developments in high angle annular dark field scanning transmission electron microscopy mode (HAADF‐STEM) tomography, such as batch tomography, image denoising by undecimated wavelet transforms, improved reconstructions by total variation minimization and a more efficient, user‐independent, segmentation scheme. To illustrate the use of this novel approach, the 3D structural characterization of a model nanocatalyst comprising gold nanoparticles dispersed on the surface of CeO₂ nanocubes is performed, and the obtained results used to compute the values of different macroscopic chemical and textural properties. Comparison with values obtained by macroscopic characterization techniques match very closely those obtained by 3D nanometrology. Importantly, the new approach described in this work also illustrates a pipeline for nearly fully automated HAADF‐STEM tomography studies, guaranteeing reliable correlations between nanoscopic and macroscopic properties.     

Sharp estimate of electric field from a conductive rod and application

We are concerned with the quantitative study of the electric field perturbation due to the presence of an inhomogeneous conductive rod embedded in a homogenous conductivity. We sharply quantify the dependence of the perturbed electric field on the geometry of the conductive rod. In particular, we accurately characterize the localization of the gradient field (i.e., the electric current) near the boundary of the rod where the curvature is sufficiently large. We develop layer‐potential techniques in deriving the quantitative estimates and the major difficulty comes from the anisotropic geometry of the rod. The result complements and sharpens several existing studies in the literature. It also generates an interesting application in EIT (electrical impedance tomography) in determining the conductive rod by a single measurement, which is also known as the Calderón's inverse inclusion problem in the literature.