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🔗 Computing 🔗 Electronics 🔗 Electrical engineering

Charlieplexing (also known as tristate multiplexing, reduced pin-count LED multiplexing, complementary LED drive and crossplexing) is a technique for accessing a large number of LEDs, switches, micro-capacitors or other I/O entities, using very few tri-state logic wires from a microcontroller, these entities being wired as discrete components, x/y arrays, or woven in a diagonally intersecting pattern to form diagonal arrays.

The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing, each I/O pin being capable, when required, of rapidly changing between the three states, logical 1, logical 0, and high impedance.

This enables these I/O entities (LEDs, switches etc.) to be connected between any two microcontroller I/Os - e.g. with 4 I/Os, each I/O can pair with 3 other I/Os, resulting in 6 unique pairings (1/2, 1/3, 1/4, 2/3, 2/4, 3/4). Only 4 pairings are possible with standard x/y multiplexing (1/3, 1/4, 2/3, 2/4). Also, due to the microcontroller's ability to reverse the polarity of the 6 I/O pairs, the number of LEDS (or diodes) that are uniquely addressable, can be doubled to 12 - adding LEDS 2/1, 3/1, 4/1, 3/2, 4/2 and 4/3.

Although it is more efficient in its use of I/O, a small amount of address manipulation is required when trying to fit Charlieplexing into a standard x/y array.

Other issues that affect standard multiplexing but are exacerbated by Charlieplexing are:

• consideration of current requirements and the forward voltages of the LEDs.
• a requirement to cycle through the in-use LEDs rapidly so that the persistence of the human eye perceives the display to be lit as a whole. Multiplexing can generally be seen by a strobing effect and skewing if the eye's focal point is moved past the display rapidly.

🔗 Books 🔗 Transhumanism 🔗 Alternative Views

Engines of Creation: The Coming Era of Nanotechnology is a 1986 molecular nanotechnology book written by K. Eric Drexler with a foreword by Marvin Minsky. An updated version was released in 2007. The book has been translated into Japanese, French, Spanish, Italian, Russian, and Chinese.

🔗 Law 🔗 U.S. Supreme Court cases

Jacobson v. Massachusetts, 197 U.S. 11 (1905), was a United States Supreme Court case in which the Court upheld the authority of states to enforce compulsory vaccination laws. The Court's decision articulated the view that the freedom of the individual must sometimes be subordinated to the common welfare and is subject to the police power of the state.

🔗 Companies

PBworks (formerly PBwiki) is a commercial real-time collaborative editing (RTCE) system created by David Weekly, with Ramit Sethi and Nathan Schmidt, who joined shortly thereafter as co-founders. Based in San Mateo, California, United States, the company operates on a freemium basis, offering basic features free of charge and more advanced features for a fee.

PBworks' investors include Mohr Davidow Ventures and the Seraph Group, as well as angel investors Ron Conway and Chris Yeh.

🔗 Computing 🔗 Systems 🔗 Business 🔗 Computing/Software 🔗 Computing/Computer science 🔗 Engineering 🔗 Systems/Systems engineering

Hofstadter's law is a self-referential adage, coined by Douglas Hofstadter in his book Gödel, Escher, Bach: An Eternal Golden Braid (1979) to describe the widely experienced difficulty of accurately estimating the time it will take to complete tasks of substantial complexity:

Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.

The law is often cited by programmers in discussions of techniques to improve productivity, such as The Mythical Man-Month or extreme programming.

🔗 Africa 🔗 Africa/Ghana 🔗 Food and drink 🔗 Africa/Ivory Coast 🔗 Africa/French Africa

Child labour is a recurring issue in cocoa production. Cote d’Ivoire (also known in English as Ivory Coast) and Ghana, together produce nearly 60% of the world's cocoa each year. During the 2018/19 cocoa-growing season, research commissioned by the U.S. Department of Labor was conducted by NORC at the University of Chicago in these two countries and found that 1.48 million children are engaged in hazardous work on cocoa farms including working with sharp tools and agricultural chemicals and carrying heavy loads. That number of children is significant, representing 43 percent of all children living in agricultural households in cocoa growing areas. During the same period cocoa production in Cote d’Ivoire and Ghana increased 62 percent while the prevalence of child labour in cocoa production among all agricultural households increased 14 percentage points. Attention on this subject has focused on West Africa, which collectively supplies 69% of the world's cocoa, and Côte d'Ivoire, supplying 35%, in particular. The 2016 Global Estimates of Child Labour indicate that one-fifth of all African children are involved in child labour. Nine percent of African children are in hazardous work. It is estimated that more than 1.8 million children in West Africa are involved in growing cocoa. A 2013–14 survey commissioned by the Department of Labor and conducted by Tulane University found that an estimated 1.4 million children aged 5 years old to 11 years old worked in agriculture in cocoa-growing areas, while approximately 800,000 of them were engaged in hazardous work, including working with sharp tools and agricultural chemicals and carrying heavy loads. According to the NORC study, methodological differences between the 2018/9 survey and earlier ones, together with errors in the administration of the 2013/4 survey have made it challenging to document changes in the number of children engaged in child labour over the past five years.

A major study of the issue, published in Fortune magazine in the U.S. in March 2016, concluded that approximately 2.1 million children in West Africa "still do the dangerous and physically taxing work of harvesting cocoa". The report was doubtful as to whether the situation can be improved significantly.

🔗 Biology 🔗 Neuroscience 🔗 Physiology 🔗 Science

A microtome (from the Greek mikros, meaning "small", and temnein, meaning "to cut") is a cutting tool used to produce extremely thin slices of material known as sections, with the process being termed microsectioning. Important in science, microtomes are used in microscopy for the preparation of samples for observation under transmitted light or electron radiation.

Microtomes use steel, glass or diamond blades depending upon the specimen being sliced and the desired thickness of the sections being cut. Steel blades are used to prepare histological sections of animal or plant tissues for light microscopy. Glass knives are used to slice sections for light microscopy and to slice very thin sections for electron microscopy. Industrial grade diamond knives are used to slice hard materials such as bone, teeth and tough plant matter for both light microscopy and for electron microscopy. Gem-quality diamond knives are also used for slicing thin sections for electron microscopy.

Microtomy is a method for the preparation of thin sections for materials such as bones, minerals and teeth, and an alternative to electropolishing and ion milling. Microtome sections can be made thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.

🔗 Statistics

In probability theory, the Chinese restaurant process is a discrete-time stochastic process, analogous to seating customers at tables in a Chinese restaurant. Imagine a Chinese restaurant with an infinite number of circular tables, each with infinite capacity. Customer 1 sits at the first table. The next customer either sits at the same table as customer 1, or the next table. This continues, with each customer choosing to either sit at an occupied table with a probability proportional to the number of customers already there (i.e., they are more likely to sit at a table with many customers than few), or an unoccupied table. At time n, the n customers have been partitioned among m ≤ n tables (or blocks of the partition). The results of this process are exchangeable, meaning the order in which the customers sit does not affect the probability of the final distribution. This property greatly simplifies a number of problems in population genetics, linguistic analysis, and image recognition.

David J. Aldous attributes the restaurant analogy to Jim Pitman and Lester Dubins in his 1983 book.

🔗 Computing

Reification is the process by which an abstract idea about a computer program is turned into an explicit data model or other object created in a programming language. A computable/addressable object—a resource—is created in a system as a proxy for a non computable/addressable object. By means of reification, something that was previously implicit, unexpressed, and possibly inexpressible is explicitly formulated and made available to conceptual (logical or computational) manipulation. Informally, reification is often referred to as "making something a first-class citizen" within the scope of a particular system. Some aspect of a system can be reified at language design time, which is related to reflection in programming languages. It can be applied as a stepwise refinement at system design time. Reification is one of the most frequently used techniques of conceptual analysis and knowledge representation.