Lectures

In rail transport, a train is a series of rail vehicles that move along guides to transport freight or passengers from one place to another. The guideway (permanent way) usually consists of conventional rail tracks, but might also be monorail or maglev. Propulsion for the train is provided by a separate locomotive, or from individual motors in self-propelled multiple units. Most trains are power...

In rail transport, a train is a series of rail vehicles that move along guides to transport freight or passengers from one place to another. The guideway (permanent way) usually consists of conventional rail tracks, but might also be monorail or maglev. Propulsion for the train is provided by a separate locomotive, or from individual motors in self-propelled multiple units. Most trains are powered by diesel engines or by electricity supplied by trackside systems. Historically the steam engine was the dominant form of locomotive power through the mid-20th century, but other sources of power (such as horses, rope, wire, gravity, pneumatics, or gas turbines) are possible.

Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals. Birds evolved from theropod dinosaurs during the Jurassic period, c 200 to 150 Ma (million years ago), and the earliest known bird is the Late Jurassic Archaeopteryx, c 155–150 Ma. Around 10,000 species of birds compose the class Aves, making them the most diverse terrestrial vertebrates. They inhabit ecosystems acros...

Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals. Birds evolved from theropod dinosaurs during the Jurassic period, c 200 to 150 Ma (million years ago), and the earliest known bird is the Late Jurassic Archaeopteryx, c 155–150 Ma. Around 10,000 species of birds compose the class Aves, making them the most diverse terrestrial vertebrates. They inhabit ecosystems across the globe, from Arctic terns to Antarctic penguins. Birds range in size from the tiny hummingbirds to the huge Ostrich.

Modern birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All birds have forelimbs modified as wings and most can fly, though the ratites and several others, particularly endemic island species, have lost the ability to fly. Birds also have unique digestive and respiratory systems that are highly adapted for flight.

Many species of bird undertake long distance annual migrations, and many more perform shorter irregular movements. Birds are social and communicate using visual signals and through calls and song, and participate in social behaviours including cooperative hunting, cooperative breeding, flocking and mobbing of predators. The vast majority of bird species are socially monogamous, usually one breeding season at a time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (“many females”) or, rarely, polyandrous (“many males”). Among some monogamous species, extra-pair copulations are common. Eggs are usually laid in a nest and incubated and most birds have an extended period of parental care after hatching.

Birds are economically important to humans: many are important sources of food, acquired either through hunting or farming, and they provide other products. Some species, particularly songbirds and parrots, are popular as pets. Birds figure prominently in all aspects of human culture from religion to poetry and popular music. About 120–130 species have become extinct as a result of human activity since 1600, and hundreds more before this. Currently around 1,200 species of birds are threatened with extinction by human activities and efforts are underway to protect them.

Bratislava is the capital of Slovakia and, with a population of 425,000, the country’s largest city. Bratislava is in the south-west of Slovakia on both banks of the Danube River. Bordering Austria and Hungary, it is the only national capital that borders two other countries. Bratislava is the political, cultural, and economic centre of Slovakia. It is the seat of the Slovak pres...

Bratislava is the capital of Slovakia and, with a population of 425,000, the country’s largest city. Bratislava is in the south-west of Slovakia on both banks of the Danube River. Bordering Austria and Hungary, it is the only national capital that borders two other countries.

Bratislava is the political, cultural, and economic centre of Slovakia. It is the seat of the Slovak presidency, the parliament, and the government, and is home to several universities, museums, theatres, galleries and other important economic, cultural, and educational institutions. The headquarters of many of Slovakia’s large businesses and financial institutions are in Bratislava.

The history of the city, long known by the German name Pressburg, has been strongly influenced by various peoples, including Austrians, Czechs, Germans, Hungarians, Jews, and Slovaks. The city was a key economic and administrative centre of the Kingdom of Hungary and was its capital under the Habsburg monarchy from 1536 to 1783. Bratislava was home to the Slovak national movement of the 19th century and to many Slovak historical figures, including Milan Rastislav Štefánik and Alexander Dubcek.