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🔗 Computing 🔗 Computing/Software 🔗 Computing/Computer science

In object-oriented computer programming, SOLID is a mnemonic acronym for five design principles intended to make software designs more understandable, flexible and maintainable. It is not related to the GRASP software design principles. The principles are a subset of many principles promoted by American software engineer and instructor Robert C. Martin. Though they apply to any object-oriented design, the SOLID principles can also form a core philosophy for methodologies such as agile development or adaptive software development. The theory of SOLID principles was introduced by Martin in his 2000 paper Design Principles and Design Patterns, although the SOLID acronym was introduced later by Michael Feathers.

🔗 Mathematics 🔗 Systems 🔗 Systems/Chaos theory

In mathematics, the Cantor function is an example of a function that is continuous, but not absolutely continuous. It is a notorious counterexample in analysis, because it challenges naive intuitions about continuity, derivative, and measure. Though it is continuous everywhere and has zero derivative almost everywhere, its value still goes from 0 to 1 as its argument reaches from 0 to 1. Thus, in one sense the function seems very much like a constant one which cannot grow, and in another, it does indeed monotonically grow, by construction.

It is also referred to as the Cantor ternary function, the Lebesgue function, Lebesgue's singular function, the Cantor–Vitali function, the Devil's staircase, the Cantor staircase function, and the Cantor–Lebesgue function. Georg Cantor (1884) introduced the Cantor function and mentioned that Scheeffer pointed out that it was a counterexample to an extension of the fundamental theorem of calculus claimed by Harnack. The Cantor function was discussed and popularized by Scheeffer (1884), Lebesgue (1904) and Vitali (1905).

🔗 Computing 🔗 Computing/Computer hardware

The floppy disk is a data storage and transfer medium that was ubiquitous from the mid-1970s well into the 2000s. Besides the 3½-inch and 5¼-inch formats used in IBM PC compatible systems, or the 8-inch format that preceded them, many proprietary floppy disk formats were developed, either using a different disk design or special layout and encoding methods for the data held on the disk.

🔗 United States 🔗 Numismatics 🔗 Numismatics/American currency 🔗 U.S. Congress

The United States Gold Reserve Act of January 30, 1934 required that all gold and gold certificates held by the Federal Reserve be surrendered and vested in the sole title of the United States Department of the Treasury. It also prohibited the Treasury and financial institutions from redeeming dollar bills for gold, established the Exchange Stabilization Fund under control of the Treasury to control the dollar’s value without the assistance (or approval) of the Federal Reserve, and authorized the president to establish the gold value of the dollar by proclamation.

Immediately following passage of the Act, the President, Franklin D. Roosevelt, changed the statutory price of gold from $20.67 per troy ounce to $35. This price change incentivized gold miners globally to expand production and foreigners to export their gold to the United States, while simultaneously devaluing the U.S. dollar by increasing inflation. The increase in gold reserves due to the price change resulted in a large accumulation of gold in the Federal Reserve and U.S. Treasury, much of which was stored in the United States Bullion Depository at Fort Knox and other locations. The increase in gold reserves increased the money supply, lowering real interest rates which in turn increased investment in durable goods.

A year earlier, in 1933, Executive Order 6102 had made it a criminal offense for U.S. citizens to own or trade gold anywhere in the world, with exceptions for some jewelry and collector's coins. These prohibitions were relaxed starting in 1964 – gold certificates were again allowed for private investors on April 24, 1964, although the obligation to pay the certificate holder on demand in gold specie would not be honored. By 1975 Americans could again freely own and trade gold.

🔗 Technology 🔗 Africa 🔗 Finance & Investment 🔗 Africa/Tanzania 🔗 Afghanistan 🔗 Africa/Kenya

M-Pesa (M for mobile, pesa is Swahili for money) is a mobile phone-based money transfer, financing and microfinancing service, launched in 2007 by Vodafone for Safaricom and Vodacom, the largest mobile network operators in Kenya and Tanzania. It has since expanded to Afghanistan, South Africa, India and in 2014 to Romania and in 2015 to Albania. M-Pesa allows users to deposit, withdraw, transfer money and pay for goods and services (Lipa na M-Pesa) easily with a mobile device.

The service allows users to deposit money into an account stored on their cell phones, to send balances using PIN-secured SMS text messages to other users, including sellers of goods and services, and to redeem deposits for regular money. Users are charged a small fee for sending and withdrawing money using the service.

M-Pesa is a branchless banking service; M-Pesa customers can deposit and withdraw money from a network of agents that includes airtime resellers and retail outlets acting as banking agents.

M-Pesa has spread quickly, and by 2010 had become the most successful mobile-phone-based financial service in the developing world. By 2012, a stock of about 17 million M-Pesa accounts had been registered in Kenya. By June 2016, a total of 7 million M-Pesa accounts have been opened in Tanzania by Vodacom. The service has been lauded for giving millions of people access to the formal financial system and for reducing crime in otherwise largely cash-based societies.

🔗 Economics

"The Market for Lemons: Quality Uncertainty and the Market Mechanism" is a well-known 1970 paper by economist George Akerlof which examines how the quality of goods traded in a market can degrade in the presence of information asymmetry between buyers and sellers, leaving only "lemons" behind. In American slang, a lemon is a car that is found to be defective after it has been bought.

Suppose buyers cannot distinguish between a high-quality car (a "peach") and a "lemon". Then they are only willing to pay a fixed price for a car that averages the value of a "peach" and "lemon" together (p_avg). But sellers know whether they hold a peach or a lemon. Given the fixed price at which buyers will buy, sellers will sell only when they hold "lemons" (since p_lemon < p_avg) and they will leave the market when they hold "peaches" (since p_peach > p_avg). Eventually, as enough sellers of "peaches" leave the market, the average willingness-to-pay of buyers will decrease (since the average quality of cars on the market decreased), leading to even more sellers of high-quality cars to leave the market through a positive feedback loop.

Thus the uninformed buyer's price creates an adverse selection problem that drives the high-quality cars from the market. Adverse selection is a market mechanism that can lead to a market collapse.

Akerlof's paper shows how prices can determine the quality of goods traded on the market. Low prices drive away sellers of high-quality goods, leaving only lemons behind. In 2001, Akerlof, along with Michael Spence, and Joseph Stiglitz, jointly received the Nobel Memorial Prize in Economic Sciences, for their research on issues related to asymmetric information.

🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Software

In computing, a Parallel Sysplex is a cluster of IBM mainframes acting together as a single system image with z/OS. Used for disaster recovery, Parallel Sysplex combines data sharing and parallel computing to allow a cluster of up to 32 systems to share a workload for high performance and high availability.

🔗 Computing 🔗 Africa 🔗 Ancient Egypt 🔗 Novels 🔗 Novels/Science fiction 🔗 Science Fiction 🔗 Women writers 🔗 Egypt

The Mummy! A Tale of the Twenty-Second Century is an 1827 three-volume novel written by Jane Webb (later Jane C. Loudon). It concerns the Egyptian mummy of Cheops, who is brought back to life in the year 2126. The novel describes a future filled with advanced technology, and was the first English-language story to feature a reanimated mummy.

After her father's death, making her an orphan at the age of 17, Webb found that:

on the winding up of his affairs that it would be necessary to do something for my support. I had written a strange, wild novel, called the Mummy, in which I had laid the scene in the twenty-second century, and attempted to predict the state of improvement to which this country might possibly arrive.

She may have drawn inspiration from the general fashion for anything pharaonic, inspired by the French researches during the Napoleonic invasion of Egypt; the 1821 public unwrappings of Egyptian mummies in a theatre near Piccadilly, which she may have attended as a girl; and, very likely, the 1818 novel by Mary Shelley, Frankenstein; or, The Modern Prometheus. As Shelley had written of Frankenstein's creation, "A mummy again endued with animation could not be so hideous as that wretch," which may have triggered her later concept. In any case, at many points she deals in greater clarity with elements from the earlier book such as the loathing for the much-desired object and the immediate arrest for crime and attempt to lie one's way out of it. However, unlike the Frankenstein monster, the hideous revived Cheops is not shuffling around dealing out horror and death, but giving canny advice on politics and life to those who befriend him. In some ways The Mummy! may be seen as her reaction to themes in Frankenstein: her mummy specifically says he is allowed life only by divine favour, rather than being indisputably vivified only by mortal science, and so on, as Hopkins' 2003 essay covers in detail.

Unlike many early science fiction works (Shelley's The Last Man, and The Reign of King George VI, 1900–1925, written anonymously in 1763), Loudon did not portray the future as her own day with only political changes. She filled her world with foreseeable changes in technology, society, and even fashion. The hero, Edric Montague, lived in a peaceful and Catholic England under the rule of Queen Claudia. Her court ladies wear trousers and hair ornaments of controlled flame. Surgeons and lawyers may be steam-powered automatons. Air travel, by balloon, is commonplace. A kind of Internet is predicted in it. Besides trying to account for the revivification of the mummy in scientific terms—galvanic shock rather than incantations—"she embodied ideas of scientific progress and discovery, that now read like prophecies" to those later in the 19th century. Many of the incidents in the book can be seen as satirical or humorous. Her social attitudes have resulted in this book being ranked among feminist novels.

The Mummy!: Or a Tale of the Twenty-Second Century was published anonymously in 1827 by Henry Colburn in three volumes, as was usual in that day so that each small volume could be easily carried around. It drew many favourable reviews, including one in 1829 in The Gardener's Magazine on the inventions proposed in it. In 1830, the 46-year-old reviewer, John Claudius Loudon, sought out the 22-year-old Webb, and they married the next year.

🔗 Finance & Investment 🔗 Economics 🔗 Business 🔗 Cooperatives

A credit union, a type of financial institution similar to a commercial bank, is a member-owned nonprofit financial cooperative. Credit unions generally provide services to members similar to retail banks, including deposit accounts, provision of credit, and other financial services. In several African countries, credit unions are commonly referred to as SACCOs (Savings and Credit Co-Operatives).

Worldwide, credit union systems vary significantly in their total assets and average institution asset size, ranging from volunteer operations with a handful of members to institutions with hundreds of thousands of members and assets worth billions of US dollars. In 2018, the number of members in credit unions worldwide was 274 million, with nearly 40 million members having been added since 2016.

Leading up to the financial crisis of 2007–2008, commercial banks engaged in approximately five times more subprime lending relative to credit unions and were two and a half times more likely to fail during the crisis. American credit unions more than doubled lending to small businesses between 2008 and 2016, from $30 billion to $60 billion, while lending to small businesses overall during the same period declined by around $100 billion. In the US, public trust in credit unions stands at 60%, compared to 30% for big banks. Furthermore, small businesses are 80% less likely to be dissatisfied with a credit union than with a big bank.

"Natural-person credit unions" (also called "retail credit unions" or "consumer credit unions") serve individuals, as distinguished from "corporate credit unions", which serve other credit unions.

🔗 Companies 🔗 Environment 🔗 Automobiles

Criticism of Tesla, Inc., especially under CEO Elon Musk, ranges from potential safety issues to questionable business practices which include alleged fraud, a history of environmental violations, disregard for workers' safety, and Musk's excessive compensation package. Tesla and Musk have also been criticized for their attempts to intimidate and silence whistleblowers, journalists, and other critics who have spoken out against the company.