Automatic weapons are firearms that are designed to fire multiple rounds with a single pull of the trigger. There are two main types of automatic weapons: 1. **Submachine Guns**: These are lightweight, fully automatic firearms that fire pistol cartridges. They are typically used in close-quarters combat. 2. **Assault Rifles**: These are more powerful, fully automatic or select-fire rifles that can fire intermediate cartridges.

Auxetics are materials that exhibit a unique property known as a negative Poisson's ratio. This means that when these materials are stretched in one direction, they expand in the perpendicular direction, contrary to most conventional materials, which tend to contract when stretched. In more technical terms, the Poisson's ratio is a measure of the ratio of transverse strain to axial strain. For most materials, this value is positive, indicating that stretching in one direction results in contraction in the other.

Avalanche breakdown is a phenomenon that occurs in semiconductors, particularly in diodes and transistors, when the electric field across a p-n junction becomes sufficiently strong to cause a rapid increase in current due to the generation of electron-hole pairs. This process is primarily associated with reverse-biased diodes and is fundamentally different from thermal breakdown.

Avangard is a Russian hypersonic glide vehicle (HGV) designed to be delivered by intercontinental ballistic missiles (ICBMs). It is characterized by its ability to travel at speeds greater than Mach 5 (five times the speed of sound) and its maneuverability, which allows it to evade missile defense systems. The Avangard system is part of Russia's efforts to develop advanced weapons technologies, providing a strategic capability that can potentially defeat existing missile defense systems.

Average human height can vary significantly by country and is influenced by a variety of factors, including genetics, nutrition, health care, and socioeconomic conditions.

The Average Treatment Effect (ATE) is a fundamental concept in causal inference and statistics that quantifies the effect of a treatment or intervention on an outcome of interest across a population. Specifically, ATE measures the average difference in outcomes between individuals who receive the treatment and those who do not.

Avoirdupois is a system of weight measurement that is commonly used in the United States and various other countries for everyday weights and measures. The term is derived from the French phrase "aveir de pois," which means "goods of weight." The avoirdupois system is based on a pound that is defined as equal to 16 ounces. In this system, one pound is equivalent to approximately 453.592 grams.

Axel Sophus Guldberg (1836-1902) was a Norwegian chemist known for his contributions to the field of chemical kinetics and equilibrium. He is particularly noted for Guldberg-Waage equation, which is foundational in the study of chemical equilibrium. Together with his colleague Peter Waage, he formulated the mass action law, which describes how the rates of chemical reactions depend on the concentrations of the reactants.

Axiomatic semantics is a formal method used in the field of computer science, particularly in the areas of programming language theory and formal verification. It provides a framework to describe the meaning of programming languages using mathematical logic. The primary goal of axiomatic semantics is to define the behavior of programs in a rigorous and precise manner. In axiomatic semantics, the meaning of a program is expressed in terms of logical assertions (or axioms) about the states of the program before and after its execution.

Bach's algorithm, also known as the **"Bach's algorithm for polynomial greatest common divisors (GCDs),"** is a method used for finding the GCD of two polynomials efficiently. It was developed by mathematician Eric Bach. The algorithm is particularly notable because it works in a way similar to the Euclidean algorithm for integers, but it operates in the realm of polynomials.

The Bach tensor is a mathematical object in the field of differential geometry, specifically within the study of Riemannian and pseudo-Riemannian manifolds. It is a derived tensor that is associated with the Ricci curvature and the Weyl tensor, and it plays an important role in the classification of the geometric properties of manifolds. More precisely, the Bach tensor is defined in the context of four-dimensional Riemannian manifolds and is related to the conformal structure of the manifold.

The Bäcklund transform is a method used in the field of differential equations, particularly in the theory of integrable systems. It is named after Swedish mathematician Lars Bäcklund, who introduced it in the context of generating new solutions from known ones for certain types of partial differential equations (PDEs). The Bäcklund transform has several important features: 1. **Generation of Solutions**: It allows for the construction of new solutions from existing ones.

"Back to Front" is a studio album by the Motown vocal group The Temptations, released in 1973. The album features a mix of soul and R&B tracks, showcasing the group's signature harmonies and style. It includes songs that were both written and produced by prominent figures in the Motown label, and it reflects the musical trends of the early 1970s.

Backyard railways, often referred to as garden railways or miniature railroads, are small-scale rail systems typically constructed in private backyards or gardens. These miniature railways are designed for hobbyists and enthusiasts who enjoy modeling, railroading, and landscaping. Here's an overview of backyard railways: ### Key Features: 1. **Scale Models**: Backyard railways can be built to various scales, with popular scales being G scale (1:22.

A "bag" is a unit of measurement that is often used to quantify bulk materials, and it can vary in size and weight depending on the context and the material being measured. The term "bag" is commonly associated with items such as agricultural products (e.g., grains, seeds), chemicals, and other bulk commodities.

In set theory and topology, a **Baire space** is a topological space that satisfies a particular property related to the concept of "largeness" in topology. Specifically, a topological space \( X \) is called a Baire space if the intersection of any countable collection of dense open sets in \( X \) is dense in \( X \).

A Principal Meridian is a fundamental reference line used in the Public Land Survey System (PLSS) in the United States. The PLSS is a method for surveying and categorizing land to facilitate property ownership and land management. The Principal Meridian serves as a starting point for defining the township and range system used in the PLSS. Each Principal Meridian is associated with a specific geographic area and is typically accompanied by a Baseline, which runs perpendicular to it.