What is the working principle of a TEM?
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Transmission electron microscopy (TEM) works by irradiating a sample with an electron beam and using the transmitted electrons to form an image on a screen. The objective lens can be defocused to create a phase difference between scattered and un-scattered electron waves, resulting in contrast on the screen . The contrast in TEM images arises from differences in electron density of the specimen's elements . TEM can be used for imaging supermolecules and provides information on the periodic ordered structure of the specimen through electron diffraction . TEM tomography allows for the visualization of the specimen's three-dimensional structure . In the field of cell biology, TEM is used to observe cells and tissue ultrastructure, but proper sample preparation is crucial for obtaining good results . TEM also has applications in cloud computing, where it provides strong safety guarantees to high-assurance Java applications .
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2 Citations | The provided paper is about the working principle and control algorithm of an analog microgrid control system. It does not provide information about the working principle of a TEM (Transmission Electron Microscope). |
| The working principle of a TEM is to transmit a beam of electrons through an ultrathin section of a biological specimen, allowing for the observation of cells and tissue ultrastructure. | |
| The working principle of a TEM is based on illuminating the specimen with electron beams in high-vacuum conditions and using the differences in electron density of the elements constituting the specimen to create contrast in the image. | |
01 Jan 2020 | The working principle of a TEM involves irradiating the sample with electrons and using the transmitted electrons to form an image on a screen, utilizing phase contrast for necessary contrast. |
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What types of tape are most commonly used for TEM sample preparation and why?4 answersThe most commonly used types of tape for Transmission Electron Microscope (TEM) sample preparation are those that allow for successful sample transfer and manipulation. In the field of semiconductor manufacturing, where TEM analysis is crucial, techniques such as in-situ lift-out and optical microscopy-based micro-manipulation systems have been employed for safe and efficient sample preparation. These methods emphasize the importance of proper selection of coating materials, tilted angle deposition, in-situ lift-out techniques, and control of electrostatic forces to transfer samples onto TEM grids effectively. Additionally, for studying heterogeneous catalyst extrudates, electron-transparent thin sections are prepared to preserve the structure and composition of the samples, enabling detailed elemental analysis critical for understanding catalyst performance.
What is temra?5 answersTEMRA (terminally differentiated effector memory CD8+ T cells re-expressing CD45RA) are a subset of CD8+ T cells that play crucial roles in various conditions. In kidney transplant rejection, TEMRA CD8+ T cells accumulate in blood and graft biopsies, exhibiting enhanced migratory properties and proinflammatory responses. In patients undergoing brain radiotherapy, TEMRA cells, especially CD8+ TEMRA, are associated with cytomegalovirus reactivation, potentially serving as a predictive marker. In rheumatoid arthritis, TEMRA cells are enriched in patients with persistent disease activity, particularly in those receiving anti-TNF therapy, and correlate with inflammation and disease flare risk. In non-small cell lung cancer, tumor-infiltrating TEMRA cells show distinct characteristics from peripheral TEMRA cells, with different transcriptomes and functional properties, suggesting a unique role in tumor immunogenicity and CD8+ TIL counts.
Whats the detection limit of TEM10 answersThe detection limit of Transmission Electron Microscopy (TEM) is a multifaceted concept that depends on various factors including the electron dosage, the efficiency of electron detectors, and the specific analytical techniques employed. High-resolution TEM studies are often constrained by the electron dosage, with sensitive samples such as catalysts and macromolecules only preserving their structures below a threshold of 100 ē/Å^2 due to the detrimental effects of high radiation doses. The efficiency of electron detectors plays a crucial role, as advancements in electron sources and optics have highlighted the limitations of current detection systems, pushing the need for novel sensor technologies that offer improved Modulation Transfer Function (MTF) and Detective Quantum Efficiency (DQE).
Analytical techniques within TEM, such as Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS), have their own detection limits. EELS is more sensitive for light elements, while EDS is better suited for heavy elements, with the detection efficiency of EDS significantly improved by new detector technology. Diagnostic negative staining electron microscopy, a technique used for pathogen detection, has shown detection limits of 10^6 particles per ml using direct adsorption and can be improved to 10^5 particles per ml for spores and 5 × 10^4 particles per ml for poxviruses with airfuge ultracentrifugation.
Furthermore, the detection limit is also influenced by the method of sample preparation and analysis, with arbitrary detection limits potentially misstating the "true" detection limits. The concept of randomly exposing areas of the specimen to the electron beam to mitigate damage introduces challenges in immediate qualitative analysis due to the difficulty in interpreting subsampled images. Lastly, the effect of chromatic aberrations and the choice of using energy-filtered electrons can impact the detection limit, especially in the context of dark field microscopy of unstained specimens.
In summary, the detection limit of TEM is not a fixed value but varies with the specific conditions of the experiment, including the type of sample, the analytical technique used, and the efficiency of the detection system.
What is the difference between tem, and hrtem in information they provide in nanoparticle?5 answersTransmission Electron Microscopy (TEM) provides information on various aspects of nanoparticles, including size, shape, crystallinity, composition, and elemental mapping. On the other hand, High-Resolution Transmission Electron Microscopy (HRTEM) offers the unique ability to observe nanoparticles at or close to the atomic scale, providing lattice or structure images of very small crystals with high resolution, down to 0.2-0.3 nm or even less. TEM is commonly used for size analysis of nanoparticles, while HRTEM excels in providing detailed atomic-scale information, crucial for understanding the structure and bonding within nanoparticles, such as carbon nanotubes in composites. HRTEM is essential for characterizing the interface between nanoparticles and matrices, identifying phases formed during reactions, and ensuring effective load transfer in nanocomposites.
What are the advantages and disadvantages of using TEM 4DSTEM compared to other techniques?5 answersTEM 4DSTEM has several advantages compared to other techniques. It allows for phase contrast imaging at atomic resolution, providing higher contrast than direct TEM imaging techniques. This enables measurements of low Z and 2D materials, as well as nanoscale electric fields. Additionally, TEM 4DSTEM can be used for sample preparation using FIB, which is a highly efficient method with a high success rate. It also offers the capability to create TEM samples from irradiated fuel, providing valuable insights into the irradiation microstructure. However, there are some disadvantages to using TEM 4DSTEM. The heavy computation burden of the algorithm proposed by Zhang et al. can make it difficult to achieve. Furthermore, there may be unresolved problems and limitations in the FIB technique for TEM sample preparation.
Principle of transmission electron microscopy?2 answersTransmission electron microscopy (TEM) is a scientific technique that uses electrons to illuminate and magnify specimens, similar to optical microscopy but with higher resolution and the ability to focus electrons using electromagnetic lenses. In TEM, electrons are irradiated onto the sample, and the transmitted electrons are used to form an image using the bright-field method. By adjusting the defocusing of the objective lens, a phase contrast can be achieved, which enhances the contrast on the screen. TEM allows for the imaging of materials at the nanometer level, revealing microstructural features such as strain fields, defects, and atomic columns. Additionally, TEM can incorporate spectroscopic techniques such as energy-dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) to analyze the electronic excitations of atoms in the specimen. Proper sample preparation is crucial for obtaining good results in TEM, especially for biological specimens, which require several stages and careful handling.