Resolution and Discovery

Microscopic and structural study on the formation of mechanochemical synthesized BaTiO3 and ZnTiO3 perovskites

2022-03-04T10:02:37+01:00

In this work, the properties of mechanochemically produced (by using mills made from different materials) barium-titanate (BaTiO₃) and zinc-titanate (ZnTiO₃) perovskites are compared. Mechanochemistry is a process that can cover the energy demand of some reaction pathways between solid materials. This process is called “high-energy milling”, for which not all type of mills are suitable. In our case, a planetary ball mill provided the necessary energy. Using a model, the required energy is determinable; the energy released during an impact of a milling ball (E_b – ball-impact energy), as well as during the whole milling (E_cum – cumulative milling energy). Thus, a milling-energy map was created, with which the applied E_b and E_cum values were visualized depending on the different grinding parameters. The parameters changed were the material of the grinding vessels, the number of grinding balls, and the rotational speed. The transformation was tracked by X-ray diffraction (XRD) measurements, and electron microscopic images (TEM and SEM) of the perovskites produced were taken. The aim of this study was to draw conclusions that will help later in the synthesis of materials with other perovskite structures by choosing optimal milling parameters.

Impact-formed complex diamond-graphite nanostructures

2021-11-05T07:13:22+01:00

Shock waves resulting from asteroidal and laboratory impacts convert sp²-bonded graphitic material to sp³-bonded diamond. Depending on the shock pressure and temperature conditions, complex nanostructures can form that are neither graphite nor diamond but belong to the diaphite material group, which are characterized by structurally intergrown layered sp²- and sp³-bonded carbon domains. Our ultrahigh-resolution transmission electron microscopy images combined with density functional theory calculations demonstrate that diaphites have two related but distinct structural families. Here, we describe diaphite nanostructures from natural and laboratory shocked samples, provide a framework for classifying the members of these materials, and draw attention to their excellent mechanical and electronic material properties.

DiffMap: a new free computer program to process scanned electron diffraction patterns

2022-01-06T10:29:35+01:00

A free computer program, called DiffMap, is presented for off-line evaluation of both phase maps and orientation maps from a large number of diffraction patterns recorded with a nearly parallel nano-beam scanned line-by-line over a rectangular area in a scanning transmission electron microscope (STEM). The program runs in the Windows operating system on IBM PC compatible computers. The patterns, which are recorded independently from this program by a CCD or CMOS camera are in Tif format, serve as input to DiffMap. Many STEMs can collect such a four-dimensional electron diffraction (4D-ED) data sets by proper selection of microscope parameters, even if this fact is not over-emphasized in the operating manuals. These phase and orientation maps can complement usual compositional maps collected in the same STEM with energy dispersive x-ray spectrometers (EDS) to give a complete description of the crystalline phases. Application is exemplified on the (fcc, hcp and bcc) phases in a sample with 4 major components (Co, Cr, Fe, Ni).

Quantitative dSTORM superresolution microscopy

2022-09-20T09:04:45+02:00

Localization based superresolution technique provides the highest spatial resolution in optical microscopy. The final image is formed by the precise localization of individual fluorescent dyes, therefore the quantification of the collected data requires special protocols, algorithms and validation processes. The effects of labelling density and structured background on the final image quality were studied theoretically using the TestSTORM simulator. It was shown that system parameters affect the morphology of the final reconstructed image in different ways and the accuracy of the imaging can be determined. Although theoretical studies help in the optimization procedure, the quantification of experimental data raises additional issues, since the ground truth data is unknown. Localization precision, linker length, sample drift and labelling density are the major factors that make quantitative data analysis difficult. Two examples (geometrical evaluation of sarcomere structures and counting the γH2AX molecules in DNA damage induced repair foci) have been presented to demonstrate the efficiency of quantitative evaluation experimentally.

Visualization of the effect of TR100 anti-cancer compound on membrane nanotubes with SR-SIM microscopy

2021-12-07T09:41:39+01:00

In our world one of the most dangerous diseases is cancer, causing abnormal growth and function of the cells. Nearly 2 million new cancer types are diagnosed each year, worldwide, causing most of the death. Therefore, cancer is in the focus of many types of research. To prevent the proliferation and spreading of malignant cells, many compounds have been developed in chemotherapy, however, a significant proportion of these have serious side effects, and a common phenomenon is that resistance is emerging early after administration. As tumor cells require tropomyosin-containing actin network for their growth and survival, and in cancers, the tropomyosin profile is considerably changed (resulting in the dramatic rearrangements of the actin cytoskeleton structure), anti-tropomyosin compounds can be a new perspective in cancer therapy. TR100 - an anti-tropomyosin cancer cell antagonist - was reported to be capable of destroying cancer cells in a highly tumor-specific manner by increasing the depolymerization of the actin filament. Tumor cells can communicate with each other via actin-containing membrane nanotubes (NTs) by the transportation of e.g. signal molecules, nucleic acids, cell organelles, resistance factors to help to survive. Immune cells also frequently use membrane nanotubes for communication, therefore, in this study we focused on the visualization of the effect of TR100 on the morphology and formation of B lymphoma cell NTs with superresolution structured illumination microscopy. TR100 treatment caused the rounding of the cells and in a concentration dependent manner changed the NT number in the early stage of their formation.