Sous-lieutenant Nicolas Léonard Sadi Carnot was a French mechanical engineer in the French Army, military scientist and physicist described as the "father of thermodynamics." Like Copernicus, he published only one book, the Reflections on the Motive Power of Fire, in which he expressed, at the age of 27 years, the first successful theory of the maximum efficiency of heat engines. In this work he laid the foundations of an new discipline, thermodynamics. Carnot's work attracted little attention during his lifetime, but it was used by Rudolf Clausius and Lord Kelvin to formalize the second law of thermodynamics and define the concept of entropy. Nicolas Léonard Sadi Carnot was born in Paris into a family, distinguished in both science and politics, he was the first son of Lazare Carnot, an eminent mathematician, military engineer and leader of the French Revolutionary Army. Lazare chose his son's third given name after the Persian poet Sadi of Shiraz. Sadi was the elder brother of statesman Hippolyte Carnot and the uncle of Marie François Sadi Carnot, who would serve as President of France from 1887 to 1894.

At the age of 16, Sadi Carnot became a cadet in the École Polytechnique in Paris, where his classmates included Michel Chasles and Gaspard-Gustave Coriolis. The École Polytechnique was intended to train engineers for military service, but its professors included such eminent scientists as André-Marie Ampère, François Arago, Joseph Louis Gay-Lussac, Louis Jacques Thénard and Siméon Denis Poisson, the school had become renowned for its mathematical instruction. After graduating in 1814, Sadi became an officer in the French army's corps of engineers, his father Lazare had served as Napoleon's minister of the interior during the "Hundred Days", after Napoleon's final defeat in 1815 Lazare was forced into exile. Sadi's position in the army, under the restored Bourbon monarchy of Louis XVIII, became difficult. Sadi Carnot was posted to different locations, he inspected fortifications, tracked plans and wrote many reports, it appears his recommendations were ignored and his career was stagnating. On 15 September 1818 he took a six-month leave to prepare for the entrance examination of Royal Corps of Staff and School of Application for the Service of the General Staff.

In 1819, Sadi transferred in Paris. He remained on call for military duty, but from on he dedicated most of his attention to private intellectual pursuits and received only two-thirds pay. Carnot befriended the scientist Nicolas Clément and attended lectures on chemistry, he became interested in understanding the limitation to improving the performance of steam engines, which led him to the investigations that became his Reflections on the Motive Power of Fire, published in 1824. Carnot retired without a pension, he was interned in a private asylum in 1832 as suffering from "mania" and "general delirum", he died of cholera shortly thereafter, aged 36, at the hospital in Ivry-sur-Seine. When Carnot began working on his book, steam engines had achieved recognized economic and industrial importance, but there had been no real scientific study of them. Newcomen had invented the first piston-operated steam engine over a century before, in 1712. Compound engines had been invented, there was a crude form of internal-combustion engine, with which Carnot was familiar and which he described in some detail in his book.

Although there existed some intuitive understanding of the workings of engines, scientific theory for their operation was nonexistent. In 1824 the principle of conservation of energy was still poorly developed and controversial, an exact formulation of the first law of thermodynamics was still more than a decade away; the prevalent theory of heat was the caloric theory, which regarded heat as a sort of weightless and invisible fluid that flowed when out of equilibrium. Engineers in Carnot's time had tried, by means such as pressurized steam and the use of fluids, to improve the efficiency of engines. In these early stages of engine development, the efficiency of a typical engine—the useful work it was able to do when a given quantity of fuel was burned—was only 3%. Carnot wanted to answer two questions about the operation of heat engines: "Is the work available from a heat source unbounded?" and "Can heat engines in principle be improved by replacing the steam with some other working fluid or gas?"

He attempted to answer these in a memoir, published as a popular work in 1824 when he was only 27 years old. It was entitled Réflexions sur la Puissance Motrice du Feu; the book was plainly intended to cover a rather wide range of topics about heat engines in a rather popular fashion. He discussed the relative merits of air and steam as working fluids, the merits of various aspects of steam engine design, included some ideas of his own regarding possible improvements of the practical nature; the most important part of the book was devoted to an abstract presentation of an idealized engine that could be used to understand and clarify the fundamental principles that are applied to all heat engine

Ramones is the debut studio album by American punk rock band Ramones, released on April 23, 1976 by Sire Records. After Hit Parader editor Lisa Robinson saw the band at a gig in New York City, she wrote about them in an article and contacted Danny Fields, insisting that he be their manager. Fields agreed and convinced Craig Leon to produce Ramones, the band recorded a demo for prospective record labels. Leon persuaded Sire president Seymour Stein to listen to the band perform, he offered the band a recording contract; the Ramones began recording in January 1976, needing $6,400 to record the album. They used similar sound-output techniques to those of the Beatles and used advanced production methods by Leon; the album cover, photographed by Punk magazine's Roberta Bayley, features the four members leaning against a brick wall in New York City. The record company paid only $125 for the front photo, which has since become one of the most imitated album covers of all time; the back cover depicts an eagle belt buckle along with the album's liner notes.

After its release, Ramones was promoted with two singles. The Ramones began touring to help sell records. Violence, drug use, relationship issues and Nazism were prominent in the album's lyrics; the album opens with "Blitzkrieg Bop", among the band's most recognized songs. Most of the album's tracks are uptempo, with many songs measuring at well over 160 beats per minute; the songs are rather short. Ramones contains a cover of the Chris Montez song "Let's Dance". Ramones peaked at number 111 on the US Billboard 200 and was unsuccessful commercially, though it received glowing reviews from critics. Many deemed it a influential record, it has since received many accolades, such as the top spot on Spin magazine's list of the "50 Most Essential Punk Records". Ramones is considered an influential punk album in the US and UK, had a significant impact on other genres of rock music, such as grunge and heavy metal; the album was ranked at number 33 in Rolling Stone's 2012 list of the "500 Greatest Albums of All Time" and was certified gold by the Recording Industry Association of America in 2014.

The Ramones began playing gigs in mid-1974, with their first show at Performance Studios in New York City. The band, performing in a style similar to the one used on their debut album performed at clubs in downtown Manhattan CBGB and Max's Kansas City. In early 1975, Lisa Robinson, an editor of Hit Parader and Rock Scene, saw the fledgling Ramones performing at CBGB and subsequently wrote about the band in several magazine issues; the group's vocalist Joey Ramone related that "Lisa came down to see us, she was blown away by us. She said. Word was getting out, people starting coming down." Convinced that the band needed a recording contract, Robinson contacted Danny Fields, former manager of the Stooges, argued that he needed to manage the band. Fields agreed because the band "had everything liked," and became the manager in November 1975. On September 19, 1975, the Ramones recorded a demo at 914 Sound Studios, produced by Marty Thau. Featuring the songs "Judy Is a Punk" and "I Wanna Be Your Boyfriend", the band used the demo to showcase their style to prospective labels.

Producer Craig Leon, who had seen the Ramones perform in the summer of 1975, brought the demo to the attention of Sire Records' president Seymour Stein. After being persuaded by Craig Leon and his ex-wife Linda Stein, the Ramones auditioned at Sire and were offered a contract, although the label had signed only European progressive rock bands. Drummer Tommy Ramone recalled: "Craig Leon is the one, single handed, he brought down the vice president and all these people—he's the only hip one in the company. He risked his career to get us on the label." The label offered to release "You're Gonna Kill That Girl" as a single, but the band declined, insisting on recording an entire album. Sire agreed to release a studio album instead. In January 1976 the band took a break from their live performances to prepare for recording at Plaza Sound studio. Sessions began that month and were completed within a week for $6,400. In 2004, Leon admitted that they recorded Ramones due to budget restrictions, but that it was all the time they needed.

The band applied microphone placement techniques similar to those. The recording process was a deliberate exaggeration of the techniques used by the Beatles in the early 1960s, with a four-track representation of the devices; the guitars can be heard separately on the stereo channels—electric bass on the left channel, rhythm guitar on the right—drums and vocals are mixed in the middle of the stereo mix. The mixing of the production used more modern techniques such as overdubbing, a technique used by studios to add a supplementary recorded sound to the material; the band used a technique known as doubling, where the vocal line used is sung twice. Recording for the album was expanded by Mickey Leigh and Leon with percussion effects, which went unmentioned in the liner notes to the album's release. Author Nicholas Rombes said that the production's quality sounded like "the ultimate do-it-yourself, reckless ethic, associated with punk," but concluded

Light rail transit is a form of urban rail transit using rolling stock similar to a tram, but operating at a higher capacity and speed, on an exclusive right-of-way. There is no standard definition, but in the United States, light rail operates along exclusive rights-of-way and uses either individual tramcars or multiple units coupled to form a train, lower capacity and lower speed than a long heavy-rail passenger train or metro system. A few light rail networks tend to have characteristics closer to rapid transit or commuter rail. Other light rail networks are tram-like in nature and operate on streets. Light rail systems are found on all inhabited continents, they have been popular in recent years due to their lower capital costs and increased reliability compared with heavy rail systems. Many original tram and streetcar systems in the United Kingdom, United States, elsewhere were decommissioned starting in the 1950s as the popularity of the automobile increased. Britain abandoned its last tram system, except for Blackpool, by 1962.

Although some traditional trolley or tram systems exist to this day, the term "light rail" has come to mean a different type of rail system. Modern light rail technology has West German origins, since an attempt by Boeing Vertol to introduce a new American light rail vehicle was a technical failure. After World War II, the Germans retained many of their streetcar networks and evolved them into model light rail systems. Except for Hamburg, all large and most medium-sized German cities maintain light rail networks; the basic concepts of light rail were put forward by H. Dean Quinby in 1962 in an article in Traffic Quarterly called "Major Urban Corridor Facilities: A New Concept". Quinby distinguished this new concept in rail transportation from historic streetcar or tram systems as: having the capacity to carry more passengers appearing like a train, with more than one car connected together having more doors to facilitate full utilization of the space faster and quieter in operationThe term light rail transit was introduced in North America in 1972 to describe this new concept of rail transportation.

The first of the new light rail systems in North America began operation in 1978 when the Canadian city of Edmonton, adopted the German Siemens-Duewag U2 system, followed three years by Calgary and San Diego, California. The concept proved popular, although Canada has few cities big enough for light rail, there are now at least 30 light rail systems in the United States. Britain began replacing its run-down local railways with light rail in the 1980s, starting with the Tyne and Wear Metro and followed by the Docklands Light Railway in London; the historic term light railway was used because it dated from the British Light Railways Act 1896, although the technology used in the DLR system was at the high end of what Americans considered to be light rail. The trend to light rail in the United Kingdom was established with the success of the Manchester Metrolink system in 1992; the term light rail was coined in 1972 by the U. S. Urban Mass Transportation Administration to describe new streetcar transformations that were taking place in Europe and the United States.

In Germany the term Stadtbahn was used to describe the concept, many in UMTA wanted to adopt the direct translation, city rail. However, UMTA adopted the term light rail instead. Light in this context is used in the sense of "intended for light loads and fast movement", rather than referring to physical weight; the infrastructure investment is usually lighter than would be found for a heavy rail system. The Transportation Research Board defined "light rail" in 1977 as "a mode of urban transportation utilizing predominantly reserved but not grade-separated rights-of-way. Electrically propelled. LRT provides a wide range of passenger capabilities and performance characteristics at moderate costs." The American Public Transportation Association, in its Glossary of Transit Terminology, defines light rail as:...a mode of transit service operating passenger rail cars singly on fixed rails in right-of-way, separated from other traffic for part or much of the way. Light rail vehicles are driven electrically with power being drawn from an overhead electric line via a trolley or a pantograph.

However, some diesel-powered transit is designated light rail, such as the O-Train Trillium Line in Ottawa, Canada, the River Line in New Jersey, United States, the Sprinter in California, United States, which use diesel multiple unit cars. Light rail is similar to the British English term light railway, long-used to distinguish railway operations carried out under a less rigorous set of regulation using lighter equipment at lower speeds from mainline railways. Light rail is a generic international English phrase for these types of rail systems, which means more or less the same thing throughout the English-speaking world; the use of the generic term light rail avoids some serious incompatibilities between British and American English. The word tram, for