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🔗 Electrical engineering

The cryotron is a switch that operates using superconductivity. The cryotron works on the principle that magnetic fields destroy superconductivity. This simple device consists of two superconducting wires (e.g. tantalum and niobium) with different critical temperature (Tc). The cryotron was invented by Dudley Allen Buck of the Massachusetts Institute of Technology Lincoln Laboratory.

As described by Buck, a straight wire of tantalum (having lower Tc) is wrapped around with a wire of niobium in a single layer coil. Both wires are electrically isolated from each other. When this device is immersed in a liquid helium bath both wires become superconducting and hence offer no resistance to the passage of electric current. Tantalum in superconducting state can carry large amount of current as compared to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire. We can think of the tantalum straight wire as a "gate" and the coiled niobium as a "control".

The article by Buck includes descriptions of several logic circuits implemented using cryotrons, including: one stage of a binary adder, carry network, binary accumulator stage, and two stages of a cryotron stepping register.

A planar cryotron using thin films of lead and tin was developed in 1957 by John Bremer at General Electric's General Engineering Lab in Schenectady, New York. This was one of the first integrated circuits, although using superconductors rather than semiconductors. In the next few years, a demonstration computer was made and arrays with 2000 devices operated. A short history of this work is in the November 2007 newsletter of the IEEE History Center.

Juri Matisoo developed a version of the cryotron incorporating a Josephson junction switched by the magnetic field from a control wire. He also explained the shortcomings of traditional cryotrons in which the superconductive material must transition between superconducting and normal states to switch the device, and thus switch relatively slowly. Matisoo's cryotron switched between a conducting state in which 'pair tunneling' of electrons through the gate took place and a 'resistive' state where only single electrons were able to tunnel. The circuit was (like the traditional cryotron) capable of some amplification (i.e gain greater than unity) had a switching rate of less than 800 picoseconds. Although the requirement for cryogenic cooling limited its practicality, it wasn't until the late 2010s that commercial transistors came close to matching this performance.

There have been periods of renewed interest in various types of cryotron, IBM experimented with using them for limited applications in supercomputers during the 1980s and (as of 2020) there has been some investigation of their potential applications both to I/O and logic in prototype quantum computers.

🔗 Internet

Do Not Track (DNT) was a proposed HTTP header field, designed to allow internet users to opt-out of tracking by websites—which includes the collection of data regarding a user's activity across multiple distinct contexts, and the retention, use, or sharing of data derived from that activity outside the context in which it occurred.

The Do Not Track header was originally proposed in 2009 by researchers Christopher Soghoian, Sid Stamm, and Dan Kaminsky. Efforts to standardize Do Not Track by the W3C in the Tracking Preference Expression (DNT) Working Group did not make it past the Candidate Recommendation stage and ended in September 2018 due to insufficient deployment and support.Mozilla Firefox became the first browser to implement the feature, while Internet Explorer, Apple's Safari, Opera and Google Chrome all later added support.

DNT is not widely adopted by the industry, with companies citing the lack of legal mandates for its use, as well as unclear standards and guidelines for how websites are to interpret the header. Thus, it is not guaranteed that enabling DNT will actually have any effect at all. The W3C disbanded its DNT working group in January 2019, citing insufficient support and adoption. Apple discontinued support for DNT the following month.

🔗 Politics 🔗 Psychology 🔗 Sociology

A collective action problem or social dilemma is a situation in which all individuals would be better off cooperating but fail to do so because of conflicting interests between individuals that discourage joint action. The collective action problem has been addressed in political philosophy for centuries, but was most clearly established in 1965 in Mancur Olson's The Logic of Collective Action.

Problems arise when too many group members choose to pursue individual profit and immediate satisfaction rather than behave in the group's best long-term interests. Social dilemmas can take many forms and are studied across disciplines such as psychology, economics, and political science. Examples of phenomena that can be explained using social dilemmas include resource depletion and low voter turnout. The collective action problem can be understood through the analysis of game theory and the free-rider problem, which results from the provision of public goods. Additionally, the collective problem can be applied to numerous public policy concerns that countries across the world currently face.

🔗 Biography 🔗 Science Fiction 🔗 Biography/arts and entertainment 🔗 Journalism

Jerry Eugene Pournelle (; August 7, 1933 – September 8, 2017) was an American polymath: scientist in the area of operations research and human factors research, science fiction writer, essayist, journalist, and one of the first bloggers. In the 1960s and early 1970s, he worked in the aerospace industry, but eventually focused on his writing career. In an obituary in gizmodo, he is described as "a tireless ambassador for the future."

Pournelle is particularly known for writing hard science fiction, and received multiple awards for his writing. In addition to his solo writing, he wrote several novels with collaborators, most notably Larry Niven. Pournelle served a term as President of the Science Fiction and Fantasy Writers of America.

Pournelle's journalism focused primarily on the computer industry, astronomy, and space exploration. From the 1970s until the early 1990s, he contributed to the computer magazine Byte, writing from the viewpoint of an intelligent user, with the oft-cited credo, “We do this stuff so you won’t have to.” He created one of the first blogs, entitled "Chaos Manor", which included commentary about politics, computer technology, space technology, and science fiction.

Pournelle was also known for his paleoconservative political views, which were sometimes expressed in his fiction. He was one of the founders of the Citizens' Advisory Council on National Space Policy, which developed some of the Reagan Administration's space initiatives, including the earliest versions of what would become the Strategic Defense Initiative.

🔗 Novels 🔗 Children's literature 🔗 Novels/Science fiction 🔗 Novels/Short story

"The Toynbee Convector" is a science fiction short story by American writer Ray Bradbury. First published in Playboy magazine in 1984, the story was subsequently featured in a 1988 short story collection also titled The Toynbee Convector.

🔗 Computer Security 🔗 Computer Security/Computing 🔗 Cryptography 🔗 Cryptography/Computer science

In computer security, a cold boot attack (or to a lesser extent, a platform reset attack) is a type of side channel attack in which an attacker with physical access to a computer performs a memory dump of a computer's random access memory by performing a hard reset of the target machine. Typically, cold boot attacks are used to retrieve encryption keys from a running operating system for malicious or criminal investigative reasons. The attack relies on the data remanence property of DRAM and SRAM to retrieve memory contents that remain readable in the seconds to minutes after power has been removed.

An attacker with physical access to a running computer typically executes a cold boot attack by cold-booting the machine and booting a lightweight operating system from a removable disk to dump the contents of pre-boot physical memory to a file. An attacker is then free to analyze the data dumped from memory to find sensitive data, such as the keys, using various forms of key finding attacks. Since cold boot attacks target random access memory, full disk encryption schemes, even with a trusted platform module installed are ineffective against this kind of attack. This is because the problem is fundamentally a hardware (insecure memory) and not a software issue. However, malicious access can be prevented by limiting physical access and using modern techniques to avoid storing sensitive data in random access memory.

🔗 Computing 🔗 Computing/Software

Arachne is a discontinued Internet suite containing a graphical web browser, email client, and dialer. Originally, Arachne was developed by Michal Polák under his xChaos label, a name he later changed into Arachne Labs. It was written in C and compiled using Borland C++ 3.1. Arachne has since been released under the GPL as Arachne GPL.

Arachne primarily runs on DOS-based operating systems, but includes builds for Linux as well. The Linux version relies on SVGALib and therefore does not require a display server.

🔗 Computing

A unidirectional network (also referred to as a unidirectional gateway or data diode) is a network appliance or device that allows data to travel in only one direction. Data diodes can be found most commonly in high security environments, such as defense, where they serve as connections between two or more networks of differing security classifications. Given the rise of industrial IoT and digitization, this technology can now be found at the industrial control level for such facilities as nuclear power plants, power generation and safety critical systems like railway networks.

After years of development the use of data diodes have increased creating two variations:

• Data diode: Network appliance or device allowing raw data to travel only in one direction, used in guaranteeing information security or protection of critical digital systems, such as industrial control systems, from inbound cyber attacks.

• Unidirectional gateway: Combination of hardware and software running in proxy computers in the source and destination networks. The hardware, a data diode, enforces physical unidirectionality and the software replicates databases and emulates protocol servers to handle bi-directional communication. The unidirectional gateway is capable of transferring multiple protocols and data types simultaneously. It contains a broader range of cybersecurity features like, secure boot, certificate management, data integrity, forward error correction (FEC), secure communication via TLS, among others. A unique characteristic is that data is transferred deterministically (to predetermined locations) with a protocol "break" that allows the data to be transferred through the data diode.

Data diodes are commonly found in high security military and government environments, and are now becoming widely spread in sectors like oil & gas, water/wastewater, airplanes (between flight control units and in-flight entertainment systems), manufacturing and cloud connectivity for industrial IoT. New regulations have increased demand and with increased capacity, major technology vendors have lowered the cost of the core technology.

🔗 Animal anatomy 🔗 Comics 🔗 Comics/Comic strips 🔗 Dinosaurs

A thagomizer () is the distinctive arrangement of four spikes on the tails of stegosaurine dinosaurs. These spikes are believed to have been a defensive measure against predators.

The arrangement of spikes originally had no distinct name; cartoonist Gary Larson invented the name "thagomizer" in 1982 as a joke in his comic strip The Far Side, and it was gradually adopted as an informal term used within scientific circles, research, and education.

🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Software 🔗 Java

Jazelle DBX (direct bytecode execution) is an extension that allows some ARM processors to execute Java bytecode in hardware as a third execution state alongside the existing ARM and Thumb modes. Jazelle functionality was specified in the ARMv5TEJ architecture and the first processor with Jazelle technology was the ARM926EJ-S. Jazelle is denoted by a "J" appended to the CPU name, except for post-v5 cores where it is required (albeit only in trivial form) for architecture conformance.

Jazelle RCT (Runtime Compilation Target) is a different technology based on ThumbEE mode; it supports ahead-of-time (AOT) and just-in-time (JIT) compilation with Java and other execution environments.

The most prominent use of Jazelle DBX is by manufacturers of mobile phones to increase the execution speed of Java ME games and applications. A Jazelle-aware Java virtual machine (JVM) will attempt to run Java bytecode in hardware, while returning to the software for more complicated, or lesser-used bytecode operations. ARM claims that approximately 95% of bytecode in typical program usage ends up being directly processed in the hardware.

The published specifications are very incomplete, being only sufficient for writing operating system code that can support a JVM that uses Jazelle. The declared intent is that only the JVM software needs to (or is allowed to) depend on the hardware interface details. This tight binding facilitates the hardware and JVM evolving together without affecting other software. In effect, this gives ARM Holdings considerable control over which JVMs are able to exploit Jazelle. It also prevents open source JVMs from using Jazelle. These issues do not apply to the ARMv7 ThumbEE environment, the nominal successor to Jazelle DBX.