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The Citicorp Center engineering crisis was the discovery, in 1978, of a significant structural flaw in Citicorp Center, then a recently completed skyscraper in New York City, and the subsequent effort to quietly make repairs over the next few months. The building, now known as Citigroup Center, occupied an entire block and was to be the headquarters of Citibank. Its structure, designed by William LeMessurier, had several unusual design features, including a raised base supported by four offset stilts, and diagonal bracing which absorbed wind loads from upper stories.

In the original design, potential wind loads for the building were calculated incorrectly. The flaw was discovered by Diane Hartley, an undergraduate student at Princeton University who was writing a thesis on the building, and was communicated to the firm responsible for the structural design. LeMessurier was subsequently lauded for acknowledging his error and orchestrating a successful repair effort. Estimates at the time suggested that the building could be toppled by a 70-mile-per-hour (110 km/h) wind, with possibly many people killed as a result. The crisis was kept secret until 1995 and Hartley had no knowledge of the significance of her work until after that time.

Hy (alternately, Hylang) is a programming language, a dialect of the language Lisp designed to interact with the language Python by translating expressions into Python's abstract syntax tree (AST). Hy was introduced at Python Conference (PyCon) 2013 by Paul Tagliamonte.

Similar to Kawa's and Clojure's mapping of s-expressions onto the Java virtual machine (JVM), Hy is meant to operate as a transparent Lisp front end to Python's abstract syntax. Lisp allows operating on code as data (metaprogramming). Thus, Hy can be used to write domain-specific languages. Hy also allows Python libraries, including the standard library, to be imported and accessed alongside Hy code with a compiling step converting the data structure of both into Python's AST.

In number theory, a narcissistic number (also known as a pluperfect digital invariant (PPDI), an Armstrong number (after Michael F. Armstrong) or a plus perfect number) in a given number base ${\displaystyle b}$ is a number that is the sum of its own digits each raised to the power of the number of digits.

"Stellar Wind" (or "Stellarwind") was the code name of a warrantless surveillance program begun under the George W. Bush administration's President's Surveillance Program (PSP). The National Security Agency (NSA) program was approved by President Bush shortly after the September 11, 2001 attacks and was revealed by Thomas Tamm to The New York Times in 2004. Stellar Wind was a prelude to new legal structures that allowed President Bush and President Barack Obama to reproduce each of those programs and expand their reach.

In theoretical computer science, the π-calculus (or pi-calculus) is a process calculus. The π-calculus allows channel names to be communicated along the channels themselves, and in this way it is able to describe concurrent computations whose network configuration may change during the computation.

The π-calculus is simple, it has few terms and so is a small, yet expressive language (see #Syntax). Functional programs can be encoded into the π-calculus, and the encoding emphasises the dialogue nature of computation, drawing connections with game semantics. Extensions of the π-calculus, such as the spi calculus and applied π, have been successful in reasoning about cryptographic protocols. Beside the original use in describing concurrent systems, the π-calculus has also been used to reason about business processes and molecular biology.

Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2019 amounted to 53,656 tonnes. Kazakhstan, Canada, and Australia were the top three uranium producers, respectively, and together account for 68% of world production. Other countries producing more than 1,000 tonnes per year included Namibia, Niger, Russia, Uzbekistan, the United States, and China. Nearly all of the world's mined uranium is used to power nuclear power plants.

Uranium is mined by in-situ leaching (57% of world production) or by conventional underground or open-pit mining of ores (43% of production). During in-situ mining, a leaching solution is pumped down drill holes into the uranium ore deposit where it dissolves the ore minerals. The uranium-rich fluid is then pumped back to the surface and processed to extract the uranium compounds from solution. In conventional mining, ores are processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, "yellowcake," which is sold on the uranium market as U₃O₈.

The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century, named after researcher James Flynn (1934–2020). When intelligence quotient (IQ) tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, usually born more recently than the first; the average result is set to 100. When the new test subjects take the older tests, in almost every case their average scores are significantly above 100.

Test score increases have been continuous and approximately linear from the earliest years of testing to the present. For example, a study published in the year 2009 found that British children's average scores on the Raven's Progressive Matrices test rose by 14 IQ points from 1942 to 2008. Similar gains have been observed in many other countries in which IQ testing has long been widely used, including other Western European countries, as well as Japan and South Korea. Improvements have also been reported for semantic and episodic memory.

There are numerous proposed explanations of the Flynn effect, such as the rise in efficiency of education, along with skepticism concerning its implications. Some researchers have suggested the possibility of a mild reversal in the Flynn effect (i.e., a decline in IQ scores) in developed countries, beginning in the 1990s. In certain cases, this apparent reversal may be due to cultural changes rendering parts of intelligence tests obsolete. Meta-analyses indicate that, overall, the Flynn effect continues, either at the same rate, or at a slower rate in developed countries.

The gates of hell are various places on the surface of the world that have acquired a legendary reputation for being entrances to the underworld. Often they are found in regions of unusual geological activity, particularly volcanic areas, or sometimes at lakes, caves, or mountains.

Sears Modern Homes were houses sold primarily through mail order catalog by Sears, Roebuck and Co., an American retailer.

From 1908 to 1942, Sears sold more than 70,000 of these houses in North America. Sears Modern Homes were purchased primarily by customers in East Coast and Midwest states but have been located as far south as Florida, as far west as California, and as far north as Alaska and Canada. No complete record of their locations was left by Sears when they closed the Modern Homes program but current-day researchers are compiling a database of those that have been found so far and the list continues to grow.

Sears Modern Homes offered more than 370 designs in a wide range of architectural styles and sizes over the line's 34-year history. Most included the latest comforts and conveniences available to house buyers in the early part of the twentieth century, such as central heating, indoor plumbing, telephone, and electricity.

Primarily shipped via railroad boxcars, these kits included most of the materials needed to build a house. Once delivered, many of these houses were assembled by the new homeowner, relatives, friends and neighbors, in a fashion similar to the traditional barn-raisings of farming families. Other homeowners relied on local carpenters or contractors to assemble the houses. In some cases, Sears provided construction services to assemble the homes. Some builders and companies purchased houses directly from Sears to build as model homes, speculative homes, or homes for customers or employees. Although most shipments came by rail, newspaper advertisements in the late 1920s and early 1930s showed Sears offering truck delivery to buyers living within a 35-mile (56 km) radius of their Newark, New Jersey, plant and their Norwood, Ohio, Sash & Door company.

Sears discontinued its Modern Homes catalog after 1940 with sales through local sales offices continuing into 1942. Years later, the sales records related to home sales were destroyed during a corporate house cleaning. As only a small percentage of these homes were documented when built, finding these houses today often requires detailed research to properly identify them. Because the various kit home companies often copied plan elements or designs from each other, there are a number of catalog and kit models from different manufacturers that look similar or identical to models offered by Sears. Determining which company manufactured a particular catalog and kit home may require additional research to determine the origin of that home.

Capability-based security is a concept in the design of secure computing systems, one of the existing security models. A capability (known in some systems as a key) is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must use a capability to access an object. Capability-based security refers to the principle of designing user programs such that they directly share capabilities with each other according to the principle of least privilege, and to the operating system infrastructure necessary to make such transactions efficient and secure. Capability-based security is to be contrasted with an approach that uses hierarchical protection domains.

Although most operating systems implement a facility which resembles capabilities, they typically do not provide enough support to allow for the exchange of capabilities among possibly mutually untrusting entities to be the primary means of granting and distributing access rights throughout the system. A capability-based system, in contrast, is designed with that goal in mind.

Capabilities as discussed in this article should not be confused with POSIX 1e/2c "Capabilities". The latter are coarse-grained privileges that cannot be transferred between processes.