An Abelian group, also known as a commutative group, is a set equipped with a binary operation that satisfies certain properties. Specifically, a group \((G, *)\) is called Abelian if it satisfies the following criteria: 1. **Closure**: For all \(a, b \in G\), the result of the operation \(a * b\) is also in \(G\).

The 2021 North-East England shellfish die-off refers to a significant event that occurred along the northeastern coastline of England, where a large number of shellfish, particularly the species found in the intertidal zones and coastal waters, experienced mass mortality. This incident was reported in the summer of 2021 and raised concerns among local fishermen, environmentalists, and researchers.

2001 Einstein is a near-Earth asteroid that was discovered on December 6, 2001. It is named after the famous physicist Albert Einstein in honor of his contributions to science, particularly in the field of theoretical physics. The asteroid has garnered interest due to its proximity to Earth and is classified as a member of the Apollo group of asteroids, which are known for their orbits that cross Earth's path.

In computing, "2020" can refer to a few different contexts, but one notable context is the "Year 2020 problem," which relates to various issues in software and hardware caused by how dates are processed. Traditionally, many computer systems represent years using a two-digit format (e.g., "20" for 2020), which can lead to ambiguities and bugs in date calculations.

Plasma Arc Welding (PAW) is a welding process that utilizes a plasma arc to join metal pieces together. Plasma is a state of matter similar to gas, but with distinct properties due to the presence of ionized particles. In PAW, a high-velocity jet of ionized gas (plasma) is created by passing a gas, typically argon or a mixture of gases, through a constricting nozzle and applying an electrical arc.

The 20th century saw a number of significant Argentine mathematicians who made important contributions across various areas of mathematics. Here are a few notable figures: 1. **Juan Carlos Ritt** (1888-1965) - Known for his work in algebra and the theory of differential equations. He developed Ritt’s theorem and made contributions to the study of differential algebra. 2. **Alberto S. A. G.

24101 Cassini is an asteroid that orbits the Sun in the asteroid belt. It was discovered on October 14, 1999, and is named in honor of Giovanni Domenico Cassini, the Italian-French astronomer known for his contributions to planetary astronomy and for discovering several of Saturn's moons. The asteroid's designation, "24101," indicates its order of discovery among other asteroids, and it is part of a larger catalog of celestial objects.

Vladimir Markovic is not a widely recognized figure in public knowledge up until October 2023; therefore, without additional context, it's unclear who specifically you are referring to. There are many individuals with that name across various fields, including academia, sports, and other professions.

Vladimir Mazya is a prominent mathematician known for his work in the fields of analysis, differential equations, and mathematical physics. He is particularly recognized for his contributions to the theory of partial differential equations, Sobolev spaces, and potential theory. Mazya has also authored several influential books and research papers in mathematics. His work has had a significant impact on both theoretical and applied mathematics, and he is regarded as an important figure in the mathematical community.

A 2-valued morphism typically refers to a concept in mathematics, particularly in category theory and related areas such as logic or computer science. However, the term might not have a universally accepted definition and can vary depending on the context it is used in. In a broad sense, a **2-valued morphism** can be understood as a mapping or function (morphism) that connects objects in a category, taking on one of two values or types.

The 4D-RCS (4D Reference Collaborative Service) Reference Model Architecture is a framework developed to facilitate the integration and interoperability of systems and services in the context of Advanced Digital Twin (ADT) environments and related applications. Though it might vary in specific implementations, the 4D-RCS concept generally focuses on the following key dimensions: 1. **Four Dimensions (4D)**: - **Time**: Incorporating the temporal aspect, focusing on how data changes and evolves over time.

4Pi STED microscopy is an advanced imaging technique in the field of fluorescence microscopy that enhances spatial resolution by combining two advanced methods: 4Pi microscopy and stimulated emission depletion (STED) microscopy. 1. **4Pi Microscopy**: This technique uses both the upper and lower hemispherical illumination of the sample, effectively capturing fluorescence from both sides.

The term "4-polytope stubs" does not appear to be a standard term in mathematics or geometry as of my last knowledge update. However, it seems to suggest a focus on properties or structures related to 4-dimensional polytopes (also known as 4-polytopes). A **4-polytope** is a four-dimensional generalization of a polytope, which can be thought of as a shape in four-dimensional space.

Aaldert Wapstra was a Dutch physicist known for his contributions to the field of nuclear physics, particularly in nuclear structure and the properties of atomic nuclei. He is notable for his work in the development of the Wapstra tables, which provided detailed information on nuclear masses and other properties of isotopes. His research helped in the understanding of nuclear reactions and the behavior of isotopes in various physical and chemical processes.

Aaron Klug (1926-2018) was a renowned British chemist and biophysicist, best known for his work in the field of structural biology. He was awarded the Nobel Prize in Chemistry in 1982 for his pioneering efforts in developing methods to determine the three-dimensional structures of biologically important molecules, particularly viruses and nucleic acids.

The term "Abacus Harmonicus" is not widely recognized in mainstream literature or established systems as of my last update in October 2023. It may refer to a concept, system, or tool used in specific contexts, such as music theory, mathematics, or an artistic application, but there is insufficient information to provide a definitive explanation.

Abigail Thompson could refer to various individuals or contexts, as it is a relatively common name. One notable person is Abigail Thompson, a mathematician known for her work in topology, particularly in the areas of geometric topology and knot theory. She has also been involved in mathematical education and advocacy for women in STEM fields. If you're looking for information on a different Abigail Thompson or a specific context (e.g., a character from a book, a public figure, etc.), please provide more details!