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🔗 Trains 🔗 Trains/Operations

Signalling block systems enable the safe and efficient operation of railways by preventing collisions between trains. The basic principle is that a route is broken up into a series of sections or "blocks". Only one train may occupy a block at a time, and the blocks are sized to allow a train to stop within them. That ensures that a train always has time to stop before getting dangerously close to another train on the same line. The block system is referred to in the UK as the method of working, in the US as the method of operation, and in Australia as safeworking.

In most situations, a system of signals is used to control the passage of trains between the blocks. When a train enters a block, signals at both ends change to indicate that the block is occupied, typically using red lamps or indicator flags. When a train first enters a block, the rear of the same train has not yet left the previous block, so both blocks are marked as occupied. That ensures there is slightly less than one block length on either end of the train that is marked as occupied, so any other train approaching that section will have enough room to stop in time, even if the first train has stopped dead on the tracks. The previously-occupied block will only be marked unoccupied when the end of the train has entirely left it, leaving the entire block clear.

Block systems have the disadvantage that they limit the number of trains on a particular route to something fewer than the number of blocks. Since the route has a fixed length, increasing the number of trains requires the creation of more blocks, which means the blocks are shorter and trains have to operate at lower speeds in order to stop safely. As a result, the number and size of blocks are closely related to the overall route capacity, and cannot be changed easily because expensive alterations to the signals along the line would be required.

Block systems are used to control trains between stations and yards, but not normally within the yards, where some other method is used. Any block system is defined by its associated physical equipment and by the application of a relevant set of rules. Some systems involve the use of signals while others do not. Some systems are specifically designed for single track railways, on which there is a danger of both head-on and rear-end collision, as opposed to double track, on which the main danger is rear-end collisions.

🔗 United States 🔗 Environment 🔗 Marketing & Advertising 🔗 United States/Texas 🔗 Road transport 🔗 U.S. Roads 🔗 U.S. Roads/Texas

Don't Mess with Texas is a slogan for a campaign aimed at reducing littering on Texas roadways by the Texas Department of Transportation. The phrase "Don't Mess with Texas" is prominently shown on road signs on major highways, television, radio and in print advertisements. The campaign is credited with reducing litter on Texas highways roughly 72% between 1987 and 1990. The campaign's target market was 18- to 35-year-old males, which was statistically shown to be the most likely to litter. While the slogan was not originally intended to become a statewide cultural phenomenon, it did.

Beyond its immediate role in reducing litter, the slogan has been popularly appropriated by Texans. The phrase has become "an identity statement, a declaration of Texas swagger". Though the origin of the slogan is not well known outside of Texas, it appears on countless items of tourist souvenirs. Since the phrase is a federally registered trademark, the department has tried at times to enforce its trademark rights with cease and desist letters, but has had very limited success. The slogan is the title of the book, Don’t Mess With Texas: The Story Behind the Legend.

"Don't Mess with Texas" has been awarded a plaque on the Madison Avenue Walk of Fame and a place in the Advertising Hall of Fame, a distinction given to only two slogans annually.

"Don't Mess with Texas" is also the official motto of the Virginia-class submarine USS Texas.

In 2011 the result of a public vote for the best "Don't Mess with Texas" ad over the last 25 was revealed, the winner was one created by the Commemorative Air Force (then called the Confederate Air Force). The ad involved the CAF's Boeing B-17 "Sentimental Journey" pursuing and retaliating against a truck from which trash was thrown.

A stick bomb is a (mechanical) spring-loaded device constructed out of flat sticks woven together under a bending moment. Other names for stick bombs include Chinese stick puzzles, Cobra wave, and frame bombs. Stick bombs are created for fun and as art, not for any practical use.

🔗 Environment 🔗 Energy

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power.

Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, wind) and other renewables, or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand. The reservoirs used with pumped storage can be quite small when contrasted with the lakes of conventional hydroelectric plants of similar power capacity, and generating periods are often less than half a day.

The round-trip efficiency of PSH generally varies between 70%–80%. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020, PSH accounts for around 95% of all active storage installations worldwide, with a total installed throughput capacity of over 181 GW and a total installed storage capacity of over 1.6 TWh.

The main requirement for PSH is hilly country. The global greenfield pumped hydro atlas lists more than 600,000 potential sites around the world, which is about 100 times more than needed to support 100% renewable electricity. Most are closed-loop systems away from rivers. Areas of natural beauty and new dams on rivers can be avoided because of the very large number of potential sites. Some projects utilise existing reservoirs (dubbed "bluefield") such as the 350 Gigawatt-hour Snowy 2.0 scheme under construction in Australia. Some recently proposed projects propose to take advantage of "brownfield" locations such as disused mines such as the Kidston project under construction in Australia.

Water requirements for PSH are small: about 1 gigalitre of initial fill water per gigawatt-hour of storage. This water is recycled uphill and back downhill between the two reservoirs for many decades, but evaporation losses (beyond what rainfall and any inflow from local waterways provide) must be replaced. Land requirements are also small: about 10 hectares per gigawatt-hour of storage, which is much smaller than the land occupied by the solar and windfarms that the storage might support. Closed loop (off-river) pumped hydro storage has the smallest carbon emissions per unit of storage of all candidates for large-scale energy storage.

🔗 Mammals

Tuffi (born 1946, India – died 1989, Paris, France) was a female Asian elephant that became famous in West Germany during 1950 when she accidentally fell from the Wuppertal Schwebebahn into the River Wupper underneath.

On 21 July 1950, the circus director Franz Althoff (de) had Tuffi, then four years old, traveled on the suspended monorail in Wuppertal, as a publicity stunt. The elephant trumpeted wildly and ran through the carriage, broke through a window and fell 12 metres (39 ft) down into the River Wupper, suffering only minor injuries. A panic had broken out in the carriage and some passengers were injured. Althoff helped the elephant out of the water. Both the circus director and the official who had allowed the ride were fined. Tuffi was sold to Cirque Alexis Gruss (fr) in 1968; she died there in 1989.

No photograph of the incident is known; a widely circulated postcard picture is a montage. A building near the location of the incident, between the stations Alter Markt and Adlerbrücke, features a painting of Tuffi. A local milk-factory has chosen the name as a brand.

The Wuppertal tourist information keeps an assortment of Tuffi-related souvenirs, local websites show original pictures.

In 1970 Marguerita Eckel and Ernst-Andreas Ziegler published a children's picture book about the incident titled Tuffi und die Schwebebahn (“Tuffi and the suspension railway”).

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Aviation/Aviation accident 🔗 Aviation/aircraft 🔗 Military history/Cold War 🔗 Greenland

The Kee Bird was a United States Army Air Forces Boeing B-29 Superfortress, serial 45-21768, of the 46th Reconnaissance Squadron, that became marooned after making an emergency landing in northwest Greenland during a secret Cold War spying mission on 21 February 1947. While the entire crew was safely evacuated after spending three days in the isolated Arctic tundra, the aircraft itself was left at the landing site. It lay there undisturbed until 1994, when a privately funded mission was launched to repair and return it. During the attempted recovery, a fire broke out, resulting in the destruction and loss of the airframe on the ground.

🔗 Genetics 🔗 Amphibians and Reptiles

The fertile hybrids of European water frogs (genus Pelophylax) reproduce by hybridogenesis (hemiclonally). This means that during gametogenesis, they discard the genome of one of the parental species and produce gametes of the other parental species (containing a genome not recombined with the genome of the first parental species). The first parental genome is restored by fertilization of these gametes with gametes from the first species (sexual host). In all-hybrid populations of the edible frog Pelophylax kl. esculentus, however, triploid hybrids provide this missing genome.

Because half of the genome is transmitted to the next generation clonally (not excluded unrecombined intact genome), and only the other half sexually (recombined genome of the sexual host), the hybridogenesis is a hemiclonal mode of reproduction.

For example, the edible frog Pelophylax kl. esculentus (mostly RL genome), which is a hybridogenetic hybrid of the marsh frog P. ridibundus (RR) and the pool frog P. lessonae (LL), usually excludes the lessonae genome (L) and generates gametes of the P. ridibundus (R). In other words, edible frogs produce gametes of marsh frogs.

The hybrid populations are propagated, however, not by the above primary hybridisations, but predominantly by backcrosses with one of the parental species they coexist (live in sympatry) with (see below in the middle).

Since the hybridogenetic hybrids require another taxon as sexual host to reproduce, usually one of the parental species, they are called kleptons (with "kl." in scientific names).

There are three known hybridogenetic hybrids of the European water frogs:

• edible frog Pelophylax kl. esculentus (usually genotype RL):
  pool frog P. lessonae (LL) × P. ridibundus (RR)
• Graf's hybrid frog Pelophylax kl. grafi (PR):
  Perez's frog P. perezi (PP) × P. ridibundus (RR) or
  Perez's frog P. perezi (PP) × edible frog P. kl. esculentus (RE)
  (it is unclear which one crossing was the primary hybridisation)
• Italian edible frog Pelophylax kl. hispanicus (RB):
  Italian pool frog P. bergeri (BB) × P. ridibundus (RR)

🔗 International relations 🔗 Australia 🔗 Law 🔗 Latin 🔗 Australia/Indigenous peoples of Australia 🔗 Australia/Australian law

Terra nullius (, plural terrae nullius) is a Latin expression meaning "nobody's land". It was a principle sometimes used in international law to justify claims that territory may be acquired by a state's occupation of it. It denotes land that has never been a part of a sovereign nation-state, such as Bir Tawil, or for which all claim to sovereign ownership has been relinquished, such as the territory east of the Oder–Neisse line that used to belong to Germany under Prussia.

🔗 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.