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🔗 Physics 🔗 Geology 🔗 Physics/Acoustics

Singing sand, also called whistling sand, barking sand or singing dune, is sand that produces sound. The sound emission may be caused by wind passing over dunes or by walking on the sand.

Certain conditions have to come together to create singing sand:

1. The sand grains have to be round and between 0.1 and 0.5 mm in diameter.
2. The sand has to contain silica.
3. The sand needs to be at a certain humidity.

The most common frequency emitted seems to be close to 450 Hz.

There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency of vibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer, creating a resonance that increases the sound's volume. The noise may be generated by friction between the grains or by the compression of air between them.

Other sounds that can be emitted by sand have been described as "roaring" or "booming".

🔗 Telecommunications 🔗 Software 🔗 Software/Computing 🔗 Hong Kong

KaiOS is a mobile operating system based on Linux, developed by KaiOS Technologies, a US-based company. It is forked from B2G OS (Boot to Gecko OS), an open source community-driven fork of Firefox OS, which was discontinued by Mozilla in 2016.

The primary features of KaiOS bring support for 4G LTE E, VoLTE, GPS and Wi-Fi with HTML5-based apps and longer battery life to non-touch devices with optimized user interface, less memory and energy consumption. It also features over-the-air updates. A dedicated app marketplace (KaiStore) enables users to download applications. Some services are preloaded as HTML5 applications, including Twitter, Facebook and YouTube. The operating system is comparatively lightweight on hardware resource usage, and is able to run on devices with just 256 MB of memory.

The operating system first appeared in 2017 and is developed by KaiOS Technologies Inc., a San Diego, California-based company headed by CEO Sebastien Codeville with offices in other countries. In June 2018, Google invested US$22 million in the operating system. India-based telecom operator Reliance Jio also invested $7 million in cash to pick up a 16% stake in the company.

In market share study results announced in May 2018, KaiOS beat Apple's iOS for second place in India, while Android dominates with 71%, albeit down by 9%. KaiOS growth is being largely attributed to popularity of the competitively-priced Jio Phone. In Q1 2018, 23 million KaiOS devices were shipped.

KaiOS is also the name of an unrelated Linux project, dating from 2014 and targeted at embedded systems.

🔗 Computing 🔗 Biology 🔗 Computing/Software 🔗 Stanford University 🔗 Pharmacology 🔗 Molecular Biology 🔗 Molecular Biology/Molecular and Cell Biology 🔗 Molecular Biology/Computational Biology

Folding@home (FAH or F@h) is a distributed computing project aimed to help scientists develop new therapeutics for a variety of diseases by the means of simulating protein dynamics. This includes the process of protein folding and the movements of proteins, and is reliant on simulations run on volunteers' personal computers. Folding@home is currently based at the University of Pennsylvania and led by Greg Bowman, a former student of Vijay Pande.

The project utilizes graphics processing units (GPUs), central processing units (CPUs), and ARM processors like those on the Raspberry Pi for distributed computing and scientific research. The project uses statistical simulation methodology that is a paradigm shift from traditional computing methods. As part of the client–server model network architecture, the volunteered machines each receive pieces of a simulation (work units), complete them, and return them to the project's database servers, where the units are compiled into an overall simulation. Volunteers can track their contributions on the Folding@home website, which makes volunteers' participation competitive and encourages long-term involvement.

Folding@home is one of the world's fastest computing systems. With heightened interest in the project as a result of the COVID-19 pandemic, the system achieved a speed of approximately 1.22 exaflops by late March 2020 and reached 2.43 exaflops by April 12, 2020, making it the world's first exaflop computing system. This level of performance from its large-scale computing network has allowed researchers to run computationally costly atomic-level simulations of protein folding thousands of times longer than formerly achieved. Since its launch on October 1, 2000, Folding@home was involved in the production of 226 scientific research papers. Results from the project's simulations agree well with experiments.

🔗 Greece 🔗 Songs

"Misirlou" (Greek: Μισιρλού < Turkish: Mısırlı 'Egyptian' < Arabic: مصر Miṣr 'Egypt') is a folk song from the Eastern Mediterranean region. The original author of the song is not known, but Arabic, Greek, and Jewish musicians were playing it by the 1920s. The earliest known recording of the song is a 1927 Greek rebetiko/tsifteteli composition. There are also Arabic belly dancing, Albanian, Armenian, Serbian, Persian, Indian and Turkish versions of the song. This song was popular from the 1920s onwards in the Arab American, Armenian American and Greek American communities who settled in the United States.

The song was a hit in 1946 for Jan August, an American pianist and xylophonist nicknamed "the one-man piano duet". It gained worldwide popularity through Dick Dale's 1962 American surf rock version, originally titled "Miserlou", which popularized the song in Western popular culture; Dale's version was influenced by an earlier Arabic folk version played with an oud. Various versions have since been recorded, mostly based on Dale's version, including other surf and rock versions by bands such as the Beach Boys, the Ventures, and the Trashmen, as well as international orchestral easy listening (exotica) versions by musicians such as Martin Denny and Arthur Lyman. Dale's surf rock version was heard in the 1994 film Pulp Fiction.

🔗 Internet 🔗 Computing 🔗 Blogging 🔗 Podcasting

RSS (RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many different websites in a single news aggregator, which constantly monitor sites for new content, removing the need for the user to manually check them. News aggregators (or "RSS readers") can be built into a browser, installed on a desktop computer, or installed on a mobile device.

Websites usually use RSS feeds to publish frequently updated information, such as blog entries, news headlines, episodes of audio and video series, or for distributing podcasts. An RSS document (called "feed", "web feed", or "channel") includes full or summarized text, and metadata, like publishing date and author's name. RSS formats are specified using a generic XML file.

Although RSS formats have evolved from as early as March 1999, it was between 2005 and 2006 when RSS gained widespread use, and the ("") icon was decided upon by several major web browsers. RSS feed data is presented to users using software called a news aggregator and the passing of content is called web syndication. Users subscribe to feeds either by entering a feed's URI into the reader or by clicking on the browser's feed icon. The RSS reader checks the user's feeds regularly for new information and can automatically download it, if that function is enabled.

🔗 Mathematics 🔗 Festivals

Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day format) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day. UNESCO's 40th General Conference decided Pi Day as the International Day of Mathematics in November 2019.

Pi Approximation Day is observed on July 22 (22/7 in the day/month format), since the fraction ​²²⁄₇ is a common approximation of π, which is accurate to two decimal places and dates from Archimedes.

Two Pi Day, also known as Tau Day for the mathematical constant Tau, is observed on June 28 (6/28 in the month/day format).

🔗 Biography 🔗 Military history 🔗 Military history/Military biography 🔗 Biography/military biography 🔗 Military history/World War II 🔗 Military history/German military history 🔗 Military history/European military history 🔗 Military history/British military history 🔗 Crime and Criminal Biography 🔗 Jersey

Edward Arnold Chapman (16 November 1914 – 11 December 1997) was an English criminal and wartime spy. During the Second World War he offered his services to Nazi Germany as a spy and subsequently became a British double agent. His British Secret Service handlers codenamed him Agent Zigzag in acknowledgement of his erratic personal history.

He had a number of criminal aliases known by the British police, amongst them Edward Edwards, Arnold Thompson and Edward Simpson. His German codename was Fritz or, later, after endearing himself to his German contacts, its diminutive form of Fritzchen.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Architecture 🔗 Urban studies and planning 🔗 Military history/Fortifications 🔗 Civil engineering 🔗 Engineering

A bastion fort or trace italienne (a phrase improperly derived from French, literally meaning Italian outline), is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-15th century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.

The design of the fort is normally a polygon with bastions at the corners of the walls. These outcroppings eliminated protected blind spots, called "dead zones", and allowed fire along the curtain from positions protected from direct fire. Many bastion forts also feature cavaliers, which are raised secondary structures based entirely inside the primary structure.

🔗 Mathematics 🔗 France

Nicolas Bourbaki (French pronunciation: ​[nikɔla buʁbaki]) is the collective pseudonym of a group of mathematicians, predominantly French alumni of the École normale supérieure (ENS). Founded in 1934–1935, the Bourbaki group originally intended to prepare a new textbook in analysis. Over time the project became much more ambitious, growing into a large series of textbooks published under the Bourbaki name, meant to treat modern pure mathematics. The series is known collectively as the Éléments de mathématique (Elements of Mathematics), the group's central work. Topics treated in the series include set theory, abstract algebra, topology, analysis, Lie groups and Lie algebras.

Bourbaki was founded in response to the effects of the First World War which caused the death of a generation of French mathematicians; as a result, young university instructors were forced to use dated texts. While teaching at the University of Strasbourg, Henri Cartan complained to his colleague André Weil of the inadequacy of available course material, which prompted Weil to propose a meeting with others in Paris to collectively write a modern analysis textbook. The group's core founders were Cartan, Claude Chevalley, Jean Delsarte, Jean Dieudonné and Weil; others participated briefly during the group's early years, and membership has changed gradually over time. Although former members openly discuss their past involvement with the group, Bourbaki has a custom of keeping its current membership secret.

The group's namesake derives from the 19th century French general Charles-Denis Bourbaki, who had a career of successful military campaigns before suffering a dramatic loss in the Franco-Prussian War. The name was therefore familiar to early 20th century French students. Weil remembered an ENS student prank in which an upperclassman posed as a professor and presented a "theorem of Bourbaki"; the name was later adopted.

The Bourbaki group holds regular private conferences for the purpose of drafting and expanding the Éléments. Topics are assigned to subcommittees, drafts are debated, and unanimous agreement is required before a text is deemed fit for publication. Although slow and labor-intensive, the process results in a work which meets the group's standards for rigour and generality. The group is also associated with the Séminaire Bourbaki, a regular series of lectures presented by members and non-members of the group, also published and disseminated as written documents. Bourbaki maintains an office at the ENS.

Nicolas Bourbaki was influential in 20th century mathematics, particularly during the middle of the century when volumes of the Éléments appeared frequently. The group is noted among mathematicians for its rigorous presentation and for introducing the notion of a mathematical structure, an idea related to the broader, interdisciplinary concept of structuralism. Bourbaki's work informed the New Math, a trend in elementary math education during the 1960s. Although the group remains active, its influence is considered to have declined due to infrequent publication of new volumes of the Éléments. However the collective's most recent publication appeared in 2016, treating algebraic topology.

🔗 Computing

DBOS is a Database-Oriented Operating System designed to simplify and improve the scalability, security and resilience of large-scale distributed applications. It started in 2020 as a joint open source project with MIT, Stanford and Carnegie Mellon University, after a brainstorm between Michael Stonebraker and Matei Zaharia on how to scale and improve scheduling and performance of millions of Apache Spark tasks.

The basic idea is to run a multi-node multi-core, transactional, highly-available distributed database, such as VoltDB, as the only application for a microkernel, and then to implement scheduling, messaging, file systems and other operating system services on top of the database.

The architectural philosophy is described by this quote from the abstract of their initial preprint:

All operating system state should be represented uniformly as database tables, and operations on this state should be made via queries from otherwise stateless tasks. This design makes it easy to scale and evolve the OS without whole-system refactoring, inspect and debug system state, upgrade components without downtime, manage decisions using machine learning, and implement sophisticated security features.

Stonebraker claims a variety of security benefits, from a "smaller, less porous attack surface", to the ability to log and analyze how the system state changes in real-time due to the transactional nature of the OS. Recovery from a severe bug or an attack can be as simple as rolling back the database to a previous state. And since the database is already distributed, the complexity of orchestration systems like Kubernetes can be avoided.

A prototype was built with competitive performance to existing systems.