Push–pull train

Push–pull is a configuration for locomotive-hauled trains, allowing them to be driven from either end of the train, whether having a locomotive at each end or not. A push–pull train has a locomotive at one end of the train, connected via some form of remote control, such as multiple-unit train control, to a vehicle equipped with a control cab at the other end of the train; this second vehicle may be an unpowered control car. In the UK and some other parts of Europe, the control car is referred to as a driving trailer. Push–pull trains with steam power provided the driver with basic controls at the cab end along with a bell or other signalling code system to communicate with the fireman located in the engine itself in order to pass commands to adjust controls not available in the cab. At low speeds, some push–pull trains are run from the engine with the guard operating bell codes and brakes from the leading cab when the locomotive is pushing the train. Many mountain railways operate on similar principles in order to keep the locomotive lower down than the carriage to prevent any opportunity for a carriage to run away from a train down the gradient and so that if the locomotive ran away, it would not take the carriage with it.

Modern train control systems use sophisticated electronics to allow full remote control of locomotives. Push–pull operation still requires considerable design care to ensure that control system failure does not endanger passengers and to ensure that in the event of a derailment, the pushing locomotive does not push a derailed train into an obstacle, worsening the accident; the 1984 Polmont rail accident, in Scotland, occurred when a push–pull train struck a cow on the track. When operating push -- pull, the train can be driven from either the alternative cab. If the train is heading in the direction in which the locomotive end of the train is facing, this is considered'pulling'. If the train is heading in the opposite direction, this is considered'pushing' and the motorman or engine driver is located in the alternative cab; this configuration means that the locomotive never needs to be uncoupled from the train and ensures fast turnaround times at a railway station terminus. Alternatively, a push–pull train a long one, may have a locomotive on both ends so that there is always one locomotive pushing and one locomotive pulling.

In this case, caution must be used to make sure that the two locomotives do not put too much stress on the cars from uneven locomotives. It is usual to arrange matters so that the trailing locomotive supplies less power and that the locomotive at the front does more pulling than the locomotive at the rear does pushing. Having an independent locomotive, as opposed to a power car at each end, is known in the railway world as a top and tail; when this configuration is used in the US, only one locomotive is allowed to provide head end power to the train. The two-locomotive formation is used by the InterCity 125; this form of operation has not been a function of train length. A prime example of this was the Reading Company which converted its small fleet of streamstyled heavyweight medium-distance coaches for its non-electric commuter operation, with a pair of EMD FP7 diesels bracketing a single five-car train, to supplant the Reading's fleet of RDCs; this train operated a weekday peak-hour round trip between Reading Terminal and Reading, from the late 1960s until 1981, with operation in the last five years by Conrail under contract to SEPTA.

A rare but possible configuration has a locomotive in the middle of the train with control cars at both ends, as was, for instance, used for a time on the Brussels-Amsterdam Benelux train when there were control cars but no three-voltage locomotives supporting the ERTMS train control system in use on the Belgian HSL 4 and the Dutch HSL-Zuid. The "Class 28" TRAXX locomotives were upgraded, the service went back to "normal" push-pull operation. In this configuration, locomotives hauling a train are located other than at the back, it may include remote control locomotives in the middle of a train. If operational considerations or economics require, trains can be made longer if intermediate locomotives are inserted in the train and are remotely controlled from the leading locomotive. Great Western RailwayThe first company to use the system was the Great Western Railway which, in 1904, equipped carriages and 0-6-0 locomotives as an autotrain to run on the Brentford Branch Line as an experimental substitute for steam railcars.

Control was by rodding and the mechanism allowed the driving compartment to be either one or two carriages-distant from the engine. With the engine in the middle of a formation, up to four carriages could be used. To reduce the surprise of a locomotive at the "wrong" end of its train, some were fitted with panelling painted in carriage livery; the experiment was successful and the company's remaining railcars were converted for autotrain use and purpose-built units constructed. Other railwaysOther companies followed the lead in 1905: the North Eastern and LBSCR using a compressed-air method of control and the Midland, using a cable-and-pulley

Kingdom Rush

Kingdom Rush is a tower defense game developed by Ironhide Game Studio and published by Armor Games, released as a free flash browser game on July 28, 2011, on the iPad on December 19, 2011, on Android in May 2013, a Unity port in January 2014 via Steam. A sequel, Kingdom Rush: Frontiers, was released on June 6, 2013; the third installment of the franchise, Kingdom Rush: Origins, was launched on November 20, 2014. It was released on PC on October 18, 2018. On November 22, 2018, Ironhide Studios released a new sequel, Kingdom Rush Vengeance, in which the player plays as Vez'nan's servant, helping him regain his throne. Kingdom Rush is a real-time tower defense game set in a medieval fantasy setting; each level presents a pre-determined path with empty slots all around, called'Strategy Points', where the player can build towers. There are four types of towers to choose from: Mages, Archers and Artillery, each costing a certain amount of money to build and upgrade. At the beginning of each level, the player gets some money.

As enemies begin to emerge from one end of the path, the towers must be able to kill them before they reach the other end of the path. The player will rely on a few spells and heroes to help the towers. Killing enemies generates money, which can be used to build and upgrade towers. Another way to earn money is to call enemy waves early, which reduces cool down time of spells. Money is earned by selling built towers or having an enemy reach the defence point; when an enemy gets there, the player loses many lives depending on the enemy. There are 18 levels in total and 48 different types of enemies that one will encounter throughout the levels. Completing a level for the first time gives the player one or many stars; these stars can be used to unlock passive upgrades that improve the effectiveness of the various towers and spells. After completing a campaign level with 18 or more lives remaining, the player earns 3 stars and the Heroic Mode and Iron Challenge are unlocked for this level; these are more challenging modes that impose various constraints.

In these modes, the player will only be given one life, so any enemy surviving to the defence point triggers a failure. Heroic Mode and Iron Challenge reward one star each. On April 25, 2012, Ironhide Game Studio released a new updated version of Kingdom Rush for Android and iOS devices that included new features and a new level. Among these new features were a hero's room; the shop provides items such as extra coins and dynamite that can be purchased through the winnings of gems in battle. The hero’s room provides a selection of heroes that aid in battle and can be obtained by passing levels; these heroes can be placed anywhere on the path. Kingdom Rush has full voice acting, most of, done by voice talent Sean Crisden; the game was featured in a problem in the 2012 Google Code Jam programming contest. The iOS version received an average score of 89/100 on review aggregator site Metacritic; as of February 2015, Kingdom Rush is the most played game in the site with 58.9 million, while Kingdom Rush: Frontiers with 25.6 million plays is situated in the 10th place.

The game was awarded the first prize at the 2011 Uruguayan Videogame Contest. On July 4, 2012, Ironhide Game Studio announced a comic version of Kingdom Rush that would be available for mobile and tablet devices, it became available on October 2012, as a free download from iTunes. On August 25, 2011, Ironhide Studios announced a sequel to Kingdom Rush entitled Kingdom Rush Frontiers; the game was slated for a Spring 2013 release. On December 12, 2012, the studio revealed its first screen capture of the game. On March 20, 2013, Ironhide Released a teaser trailer of Kingdom Rush Frontiers. On June 6, 2013, the sequel was released for iOS. On September 26, 2013, it was released for Android, on November 22, 2013, for Flash; the game has a Metacritic score of 85/100 based on 16 critic reviews. The game was released for Nintendo Switch on February 27, 2020; the third installment of the franchise, Kingdom Rush Origins, was launched on November 20, 2014 on iOS and Android platforms. It is the prequel to the original game.

Ironhide Studios announced their intention to make a fourth Kingdom Rush game in early 2017. On July 17, 2018, Ironhide Studios announced that the new sequel would be called Kingdom Rush Vengeance; the player plays as Lord Vez'nan's servant to help him regain his throne. It was released on November 22, 2018. In April 2019, Lucky Duck Games, a board game company that specialises in transforming computer games in to table-top games, launched a Kickstarter campaign to produce a 2–4 player co-operative board game version of Kingdom Rush; the target amount was reached within an hour, subsequently reached over 5000% of the target. The game, called'Kingdom Rush: Rift in Time' is set after the events of the computer games, with the kingdom battling the'Time Mage'. Hordes are defeated by being overlayed with polyominos. Players play as some of the heroes from the original game, work together to upgrade towers, which are rebuilt each round. Towers are built by the buying of tower cards, upgraded by players passing their cards to others at the start of the round.

The game is set for release April 2020. Official site Developer site Lucky Duck Games

Campanula gelida

Campanula gelida is a stenoendemic, critically endangered species of perennial bellflower growing in the mountains of Hrubý Jeseník in the Czech Republic. It evolved through specialization of an isolated population of Campanula scheuchzeri, an Alpine species, which expanded to the area of the Sudetes during a colder period the last ice age, it is related to Campanula bohemica, endemic to the Krkonoše Mountains. Sometimes it is considered its subspecies and referred to as Campanula bohemica subsp. Gelida, they all belong to the group of related species Campanula rotundifolia agg. The only known occurrence of Campanula gelida in its natural environment is at Peter's Stones in the Praděd nature reserve, at an altitude of 1,438 metres above mean sea level, where it has to resist low temperatures and snow, it grows on the southern and eastern slopes of the highest rock of Peter's Stones and in nearby grass vegetation consisting of fescue, within 10 metres of the foot of the rock. The location is not accessible to the public.

Campanula gelida is similar to its nearest relative Campanula bohemica. Miloslav Kovanda, the first botanist who described Campanula gelida in 1968 even reclassified it as its subspecies. Most botanists consider it to be an independent species again. Campanula gelida can be distinguished from Campanula bohemica by its rich tufts, smaller flowers and capsules. Flowers grow independently or in racemes consisting of not more than four flowers. Stem is not longer than 20 cm. Ground leaves, forming a rosette, stay. Campanula gelida grows in small fissures of rocky, acid ground, it prefers sunlit places. The species reproduces vegetatively, because its possibilities of generative reproduction are limited by the climatic conditions of its location. Flowers are produced from the middle of July until the end of August. To other bellflowers, its gynoecium develops after pollen has been set free from stamens, which prevents self-pollination. Although Campanula gelida is critically endangered and was on the edge of extinction in the 1970s, at present the population of the species seems to have stabilized.

Current threats include skiers trespassing in the protected area and expansion of other species including Tufted Hair-grass, Red Raspberry and Hypericum maculatum. Campanula gelida is on the list of protected plants of the Czech Republic, thus it is forbidden to be picked, dug or otherwise damaged or disturbed in its development, it was included into the Red List of Endangered Plants of the Czech Republic, category C1, the IUCN Red List of Threatened Plants and the Bern Convention on the Conservation of European Wildlife and Natural Habitats. Its location was included into the network of protected areas Natura 2000. Employees from the Administration of the Jeseníky Protected Landscape Area cultivate the plants in Stará Ves near Rýmařov. Campanula bohemica ssp. gelida in the IUCN database of threatened species