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🔗 Computing 🔗 Computer Security 🔗 Computer Security/Computing

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.

🔗 Mathematics 🔗 Statistics

Itô calculus, named after Kiyosi Itô, extends the methods of calculus to stochastic processes such as Brownian motion (see Wiener process). It has important applications in mathematical finance and stochastic differential equations.

The central concept is the Itô stochastic integral, a stochastic generalization of the Riemann–Stieltjes integral in analysis. The integrands and the integrators are now stochastic processes:

${\displaystyle Y_{t}=\int _{0}^{t}H_{s}\,dX_{s},}$

where H is a locally square-integrable process adapted to the filtration generated by X (Revuz & Yor 1999, Chapter IV), which is a Brownian motion or, more generally, a semimartingale. The result of the integration is then another stochastic process. Concretely, the integral from 0 to any particular t is a random variable, defined as a limit of a certain sequence of random variables. The paths of Brownian motion fail to satisfy the requirements to be able to apply the standard techniques of calculus. So with the integrand a stochastic process, the Itô stochastic integral amounts to an integral with respect to a function which is not differentiable at any point and has infinite variation over every time interval. The main insight is that the integral can be defined as long as the integrand H is adapted, which loosely speaking means that its value at time t can only depend on information available up until this time. Roughly speaking, one chooses a sequence of partitions of the interval from 0 to t and constructs Riemann sums. Every time we are computing a Riemann sum, we are using a particular instantiation of the integrator. It is crucial which point in each of the small intervals is used to compute the value of the function. The limit then is taken in probability as the mesh of the partition is going to zero. Numerous technical details have to be taken care of to show that this limit exists and is independent of the particular sequence of partitions. Typically, the left end of the interval is used.

Important results of Itô calculus include the integration by parts formula and Itô's lemma, which is a change of variables formula. These differ from the formulas of standard calculus, due to quadratic variation terms.

In mathematical finance, the described evaluation strategy of the integral is conceptualized as that we are first deciding what to do, then observing the change in the prices. The integrand is how much stock we hold, the integrator represents the movement of the prices, and the integral is how much money we have in total including what our stock is worth, at any given moment. The prices of stocks and other traded financial assets can be modeled by stochastic processes such as Brownian motion or, more often, geometric Brownian motion (see Black–Scholes). Then, the Itô stochastic integral represents the payoff of a continuous-time trading strategy consisting of holding an amount H_t of the stock at time t. In this situation, the condition that H is adapted corresponds to the necessary restriction that the trading strategy can only make use of the available information at any time. This prevents the possibility of unlimited gains through clairvoyance: buying the stock just before each uptick in the market and selling before each downtick. Similarly, the condition that H is adapted implies that the stochastic integral will not diverge when calculated as a limit of Riemann sums (Revuz & Yor 1999, Chapter IV).

🔗 Psychology

An autostereogram is a single-image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene from a two-dimensional image. In order to perceive 3D shapes in these autostereograms, one must overcome the normally automatic coordination between accommodation (focus) and horizontal vergence (angle of one's eyes). The illusion is one of depth perception and involves stereopsis: depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular parallax.

The simplest type of autostereogram consists of horizontally repeating patterns (often separate images) and is known as a wallpaper autostereogram. When viewed with proper convergence, the repeating patterns appear to float above or below the background. The well-known Magic Eye books feature another type of autostereogram called a random dot autostereogram. One such autostereogram is illustrated above right. In this type of autostereogram, every pixel in the image is computed from a pattern strip and a depth map. A hidden 3D scene emerges when the image is viewed with the correct convergence.

Autostereograms are similar to normal stereograms except they are viewed without a stereoscope. A stereoscope presents 2D images of the same object from slightly different angles to the left eye and the right eye, allowing us to reconstruct the original object via binocular disparity. When viewed with the proper vergence, an autostereogram does the same, the binocular disparity existing in adjacent parts of the repeating 2D patterns.

There are two ways an autostereogram can be viewed: wall-eyed and cross-eyed. Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. Wall-eyed viewing requires that the two eyes adopt a relatively parallel angle, while cross-eyed viewing requires a relatively convergent angle. An image designed for wall-eyed viewing if viewed correctly will appear to pop out of the background, while if viewed cross-eyed it will instead appear as a cut-out behind the background and may be difficult to bring entirely into focus.

🔗 United States 🔗 Biography 🔗 Biography/science and academia 🔗 Astronomy 🔗 United States/Arizona 🔗 Astronomy/Solar System

Robert Burnham Jr. (June 16, 1931 – March 20, 1993) was an American astronomer, best known for writing the classic three-volume Burnham's Celestial Handbook. He is the discoverer of numerous asteroids including the Mars crossing asteroid 3397 Leyla, as well as six comets.

Burnham's late years were tragic; he died destitute and alone. However, he is remembered by a generation of deep sky observers for his unique contribution to astronomy, the Celestial Handbook. The main-belt asteroid 3467 Bernheim was named in his honor.

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Philosophy of mind

Bonini's paradox, named after Stanford business professor Charles Bonini, explains the difficulty in constructing models or simulations that fully capture the workings of complex systems (such as the human brain).

🔗 Mathematics

In number theory, a weird number is a natural number that is abundant but not semiperfect.

In other words, the sum of the proper divisors (divisors including 1 but not itself) of the number is greater than the number, but no subset of those divisors sums to the number itself.

🔗 Computer Security 🔗 Computer Security/Computing

Zombie Zero is an attack vector where a cyber attacker utilized malware that was clandestinely embedded in new barcode readers which were manufactured overseas.

It remains unknown if this attack was promulgated by organized crime or a nation state. Clearly there was significant planning and investment in order to design the malware, and then embed it into the hardware within the barcode scanner. Internet of things (IoT) devices may be similarly preinstalled with malware that can capture the network passwords and then open a backdoor to attackers. Given the high volume of these devices manufactured overseas high caution is to be exercised before placing these devices on corporate or government networks.

🔗 Economics 🔗 Philosophy 🔗 Politics 🔗 Philosophy/Social and political philosophy 🔗 Philosophy/Philosophy of religion 🔗 Cooperatives 🔗 Catholicism

Distributism is an economic theory asserting that the world's productive assets should be widely owned rather than concentrated.

Developed in Europe in the late 19th and early 20th centuries, distributism was based upon the principles of Catholic social teaching, especially the teachings of Pope Leo XIII in his encyclical Rerum novarum (1891) and Pope Pius XI in Quadragesimo anno (1931). It views both capitalism and socialism as equally flawed and exploitative, and it favors economic mechanisms such as cooperatives and member-owned mutual organizations as well as small businesses, and large-scale antitrust regulations.

Some Christian democratic political parties have advocated distributism in their economic policies.

🔗 Architecture 🔗 New Jersey 🔗 National Register of Historic Places

The Bell Labs Holmdel Complex, in Holmdel Township, Monmouth County, New Jersey, United States, functioned for 44 years as a research and development facility, initially for the Bell System and later Bell Labs. The centerpiece of the campus is an Eero Saarinen–designed structure that served as the home to over 6,000 engineers and researchers. This modernist building, dubbed "The Biggest Mirror Ever" by Architectural Forum due to its mirror box exterior, was the site of a Nobel Prize discovery, the laser cooling work of Steven Chu.

Restructuring of the company's research efforts reduced the use of the Holmdel Complex, and in 2006 the building was put up for sale. The building has undergone renovations into a multi-purpose living and working space, dubbed Bell Works by its redevelopers. Since 2013 it has been operated by Somerset Development, who redeveloped the building into a mixed-use office for high-tech startup companies. The complex was listed on the National Register of Historic Places in 2017. A number of movies, television programs, and commercials have been filmed at Bell Works, including Severance, The Crowded Room, and Law & Order: Organized Crime.

🔗 Military history 🔗 Politics 🔗 Politics of the United Kingdom 🔗 Military history/European military history 🔗 Military history/British military history

The letters of last resort are four identically worded handwritten letters from the Prime Minister of the United Kingdom to the commanding officers of the four British ballistic missile submarines. They contain orders on what action to take in the event that an enemy nuclear strike has destroyed the British government and has killed or otherwise incapacitated both the prime minister and the "second person" (normally a high-ranking member of the Cabinet) whom the prime minister has designated to make a decision on how to act in the event of the prime minister's death. In the event that the orders are carried out, the action taken could be the last official act of Government of the United Kingdom.

The letters are stored inside two nested safes in the control room of each submarine. The letters are destroyed unopened after a prime minister leaves office, so their content remains known only to the prime minister who issued them.