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Topic Review
Extinction
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trumpler. However, its effects had been noted in 1847 by Friedrich Georg Wilhelm von Struve, and its effect on the colors of stars had been observed by a number of individuals who did not connect it with the general presence of galactic dust. For stars that lie near the plane of the Milky Way and are within a few thousand parsecs of the Earth, extinction in the visual band of frequencies (photometric system) is roughly 1.8 magnitudes per kiloparsec. For Earth-bound observers, extinction arises both from the interstellar medium (ISM) and the Earth's atmosphere; it may also arise from circumstellar dust around an observed object. Strong extinction in earth's atmosphere of some wavelength regions (such as X-ray, ultraviolet, and infrared) is overcome by the use of space-based observatories. Since blue light is much more strongly attenuated than red light, extinction causes objects to appear redder than expected, a phenomenon referred to as interstellar reddening.
  • 1.5K
  • 18 Oct 2022
Topic Review
Exploration Mission-1
Exploration Mission-1 or EM-1 (previously known as Space Launch System 1 or SLS-1) is the uncrewed first planned flight of the Space Launch System and the second flight of the Orion Multi-Purpose Crew Vehicle. The launch is planned for June 2020 from Launch Complex 39B at the Kennedy Space Center. The Orion spacecraft will spend approximately 3 weeks in space, including 6 days in a retrograde orbit around the Moon. It is planned to be followed by Exploration Mission 2 in 2023.
  • 618
  • 28 Sep 2022
Topic Review
Experimental Approach to Silicon Heterojunction Tandem Solar Cells
A solar cell, or a photovoltaic (PV) cell, is an electrical device that converts light energy directly into electricity by the photovoltaic effect. There are different types of solar cells. Tandem solar cells could have a very good conversion efficiency in comparison with other types of solar cells. Tandem solar cells are considered the industry’s next step in photovoltaics due to their excellent conversion efficiency. A very good example is the perovskite absorber material that has been developed for efficient tandem solar cells. 
  • 182
  • 05 Mar 2024
Topic Review
Exoplanetology
Exoplanetology, or exoplanetary science, is an integrated field of astronomical science dedicated to the search for and study of exoplanets (extrasolar planets). It employs an interdisciplinary approach which includes astrobiology, astrophysics, astronomy, astrochemistry, astrogeology, geochemistry, and planetary science.
  • 2.0K
  • 09 Nov 2022
Topic Review
Exercise Strategies of Athletes during COVID-19
Elite athletes use high-intensity training to maintain their fitness level. However, intense training can harm the immune system, making athletes suspectable to COVID-19 and negatively affecting their performance. Although high-intensity exercise can suppress the immune system, elite athletes should not stop training in the time of infection but use low- and moderate-intensity training. Moderate-intensity exercise can improve immune function and maintain physical fitness. In addition, it is also better for athletes not to undertake high-intensity training at the time of vaccination, but instead perform moderate to low-intensity training.
  • 882
  • 18 Feb 2022
Topic Review
Exercise and Cartilage Regeneration Therapy
In response to exercise, articular chondrocytes increase their production of glycosaminoglycans, bone morphogenic proteins, and anti-inflammatory cytokines and decrease their production of proinflammatory cytokines and matrix-degrading metalloproteinases. These changes are associated with improvements in cartilage organization and reductions in cartilage degeneration. Studies in humans indicate that exercise enhances joint recruitment of bone marrow-derived mesenchymal stem cells and upregulates their expression of osteogenic and chondrogenic genes, osteogenic microRNAs, and osteogenic growth factors. Rodent experiments demonstrate that exercise enhances the osteogenic potential of bone marrow-derived mesenchymal stem cells while diminishing their adipogenic potential, and that exercise done after stem cell implantation may benefit stem cell transplant viability. Physical exercise also exerts a beneficial effect on the skeletal system by decreasing immune cell production of osteoclastogenic cytokines interleukin-1β, tumor necrosis factor-α, and interferon-γ, while increasing their production of antiosteoclastogenic cytokines interleukin-10 and transforming growth factor-β.
  • 2.2K
  • 28 Jan 2021
Topic Review
Excitation Threshold Reduction Theory in Organic Semiconductor Lasers
Organic semiconductor lasers have shown great application potential in various fields, such as low-cost sensing, high-performance lighting and display, and lab-on-a-chip devices. Since the introduction of organic lasers in the 1960s, research on semiconductor laser devices has expanded to include various materials and structures. The organic laser has attracted much attention due to its wide range of emission spectrum and simple synthesis and processing. 
  • 137
  • 10 Nov 2023
Topic Review
Exchange Bias in Nanostructures
Exchange bias (EB) is a unidirectional anisotropy occurring in exchange-coupled ferromagnetic/antiferromagnetic systems, such as thin films, core–shell particles, or nanostructures. In addition to a horizontal shift of the hysteresis loop, defining the exchange bias, asymmetric loops and even vertical shifts can often be found. 
  • 444
  • 30 Aug 2023
Topic Review
Event Symmetry
In physics, event symmetry includes invariance principles that have been used in some discrete approaches to quantum gravity where the diffeomorphism invariance of general relativity can be extended to a covariance under every permutation of spacetime events.
  • 737
  • 07 Nov 2022
Biography
Evan O'Neill Kane
Evan O'Neill Kane (December 23, 1924 – March 23, 2006), known as E. O. Kane in his publications, was an American physicist who established some of the basic understanding of the theory of semiconductors that are now used in consumer and other electronics. He was one of the main developers of the k·p perturbation theory which is used to calculate band structures. Kane's great, great uncle,
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  • 09 Dec 2022
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