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π Optic Nerve (GCHQ)
Optic Nerve is a mass surveillance programme run by the British signals intelligence agency Government Communications Headquarters (GCHQ), with help from the US National Security Agency, that surreptitiously collects private webcam still images from users while they are using a Yahoo! webcam application. As an example of the scale, in one 6-month period, the programme is reported to have collected images from 1.8 million Yahoo! user accounts globally. The programme was first reported on in the media in February 2014, from documents leaked by the former National Security Agency contractor Edward Snowden, but dates back to a prototype started in 2008, and was still active in at least 2012.
The leaked documents describe the users under surveillance as "unselected", meaning that data was collected indiscriminately in bulk from users regardless of whether they were an intelligence target or not. The vast majority of affected users would have been completely innocent of any crime or suspicion of a crime. Optic Nerve as described in the documents collected one still image every 5 minutes per user, attempting to comply with human rights legislation. The images were collected in a searchable database, and used for experiments in facial recognition, to monitor known targets, and to discover new targets. The choice of Yahoo! for surveillance was taken because "Yahoo webcam is known to be used by GCHQ targets". Unlike the US NSA, the UK GCHQ is not required by law to minimise the collection from domestic citizens, so UK citizens could have been targeted on the same level as non-UK citizens.
The story was broken by The Guardian in February 2014, and is based on leaked documents dating to between 2008 and 2012. Yahoo! expressed outrage at the programme, when approached by The Guardian, and subsequently called it "a whole new level of violation of our users' privacy." A GCHQ spokesperson stated "It is a long-standing policy that we do not comment on intelligence matters".
Though there were some limits to which photos security analysts were allowed to see, with bulk searches limited to metadata, security analysts were allowed to see "webcam images associated with similar Yahoo identifiers to your known target".
π Confocal microscopy
Confocal microscopy, most frequently confocal laser scanning microscopy (CLSM) or laser scanning confocal microscopy (LSCM), is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation. Capturing multiple two-dimensional images at different depths in a sample enables the reconstruction of three-dimensional structures (a process known as optical sectioning) within an object. This technique is used extensively in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection and materials science.
Light travels through the sample under a conventional microscope as far into the specimen as it can penetrate, while a confocal microscope only focuses a smaller beam of light at one narrow depth level at a time. The CLSM achieves a controlled and highly limited depth of field.
Discussed on
- "Confocal microscopy" | 2024-01-22 | 44 Upvotes 19 Comments
π MU puzzle
The MU puzzle is a puzzle stated by Douglas Hofstadter and found in GΓΆdel, Escher, Bach involving a simple formal system called "MIU". Hofstadter's motivation is to contrast reasoning within a formal system (ie., deriving theorems) against reasoning about the formal system itself. MIU is an example of a Post canonical system and can be reformulated as a string rewriting system.
Discussed on
- "MU puzzle" | 2018-12-15 | 83 Upvotes 45 Comments
π Holon
A holon (Greek: ὠλον, from ὠλοΟ, holos, 'whole' and -ΞΏΞ½, -on, 'part') is something that is simultaneously a whole in and of itself, as well as a part of a larger whole. In other words, holons can be understood as the constituent partβwholes of a hierarchy.
The holon represents a way to overcome the dichotomy between parts and wholes, as well as a way to account for both the self-assertive and the integrative tendencies of organisms. The term was coined by Arthur Koestler in The Ghost in the Machine (1967). In Koestler's formulations, a holon is something that has integrity and identity while simultaneously being a part of a larger system; it is a subsystem of a greater system.
Holons are sometimes discussed in the context of self-organizing holarchic open (SOHO) systems.
π DNA origami
DNA origami is the nanoscale folding of DNA to create non-arbitrary two- and three-dimensional shapes at the nanoscale. The specificity of the interactions between complementary base pairs make DNA a useful construction material, through design of its base sequences. DNA is a well-understood material that is suitable for creating scaffolds that hold other molecules in place or to create structures all on its own.
DNA origami was the cover story of Nature on March 16, 2006. Since then, DNA origami has progressed past an art form and has found a number of applications from drug delivery systems to uses as circuitry in plasmonic devices; however, most applications remain in a concept or testing phase.
Discussed on
- "DNA origami" | 2016-12-22 | 37 Upvotes 5 Comments
π ChandraβToueg consensus algorithm
The ChandraβToueg consensus algorithm, published by Tushar Deepak Chandra and Sam Toueg in 1996, is an algorithm for solving consensus in a network of unreliable processes equipped with an eventually strong failure detector. The failure detector is an abstract version of timeouts; it signals to each process when other processes may have crashed. An eventually strong failure detector is one that never identifies some specific non-faulty process as having failed after some initial period of confusion, and, at the same time, eventually identifies all faulty processes as failed (where a faulty process is a process which eventually fails or crashes and a non-faulty process never fails). The ChandraβToueg consensus algorithm assumes that the number of faulty processes, denoted by f, is less than n/2 (i.e. the minority), i.e. it assumes f < n/2, where n is the total number of processes.
π KarΕshi, death by overwork
Karoshi (ιε΄ζ», KarΕshi), which can be translated literally as "overwork death" in Japanese, is occupational sudden mortality. The major medical causes of karoshi deaths are heart attack and stroke due to stress and a starvation diet. This phenomenon is also widespread in other parts of Asia.
Discussed on
- "KarΕshi, death by overwork" | 2010-05-25 | 26 Upvotes 12 Comments
π Blissymbols, an Ideographic Writing System
Blissymbols or Blissymbolics is a constructed language conceived as an ideographic writing system called Semantography consisting of several hundred basic symbols, each representing a concept, which can be composed together to generate new symbols that represent new concepts. Blissymbols differ from most of the world's major writing systems in that the characters do not correspond at all to the sounds of any spoken language.
Blissymbols was published by Charles K. Bliss in 1949 and found use in the education of people with communication difficulties.
Discussed on
- "Blissymbols β Ideographic Writing System" | 2024-04-04 | 35 Upvotes 14 Comments
- "Blissymbols" | 2020-08-05 | 81 Upvotes 46 Comments
- "Blissymbols, an Ideographic Writing System" | 2019-01-22 | 13 Upvotes 4 Comments
π The Erlang Distribution
The Erlang distribution is a two-parameter family of continuous probability distributions with support . The two parameters are:
- a positive integer the "shape", and
- a positive real number the "rate". The "scale", the reciprocal of the rate, is sometimes used instead.
The Erlang distribution with shape parameter simplifies to the exponential distribution. It is a special case of the gamma distribution. It is the distribution of a sum of independent exponential variables with mean each.
The Erlang distribution was developed by A. K. Erlang to examine the number of telephone calls which might be made at the same time to the operators of the switching stations. This work on telephone traffic engineering has been expanded to consider waiting times in queueing systems in general. The distribution is also used in the field of stochastic processes.
Discussed on
- "The Erlang Distribution" | 2009-03-11 | 142 Upvotes 3 Comments
π Basic Economics by Thomas Sowell
Basic Economics is a non-fiction book by American economist Thomas Sowell published by Basic Books in 2000. The original subtitle was A Citizen's Guide to the Economy, but from the third edition in 2007 on it was subtitled A Common Sense Guide to the Economy.
Basic Economics is focused on how societies create prosperity or poverty for their peoples by the way they organize their economies.