In organic chemistry, a hydrocarbon is an organic compound consisting of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons from which one hydrogen atom has been removed are functional groups called hydrocarbyls; because carbon has 4 electrons in its outermost shell carbon has four bonds to make, is only stable if all 4 of these bonds are used. Aromatic hydrocarbons, alkanes and alkyne-based compounds are different types of hydrocarbons. Most hydrocarbons found on Earth occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form limitless chains; as defined by IUPAC nomenclature of organic chemistry, the classifications for hydrocarbons are: Saturated hydrocarbons are the simplest of the hydrocarbon species. They are composed of single bonds and are saturated with hydrogen; the formula for acyclic saturated hydrocarbons is CnH2n+2. The most general form of saturated hydrocarbons is CnH2n +2.
Those with one ring are the cycloalkanes. Saturated hydrocarbons are the basis of petroleum fuels and are found as either linear or branched species. Substitution reaction is their characteristics property. Hydrocarbons with the same molecular formula but different structural formulae are called structural isomers; as given in the example of 3-methylhexane and its higher homologues, branched hydrocarbons can be chiral. Chiral saturated hydrocarbons constitute the side chains of biomolecules such as chlorophyll and tocopherol. Unsaturated hydrocarbons have one or more triple bonds between carbon atoms; those with double bond are called alkenes. Those with one double bond have the formula CnH2n; those containing triple bonds are called alkyne. Those with one triple bond have the formula CnH2n−2. Aromatic hydrocarbons known as arenes, are hydrocarbons that have at least one aromatic ring. Hydrocarbons can be gases, waxes or low melting solids or polymers; because of differences in molecular structure, the empirical formula remains different between hydrocarbons.
This inherent ability of hydrocarbons to bond to themselves is known as catenation, allows hydrocarbons to form more complex molecules, such as cyclohexane, in rarer cases, arenes such as benzene. This ability comes from the fact that the bond character between carbon atoms is non-polar, in that the distribution of electrons between the two elements is somewhat due to the same electronegativity values of the elements, does not result in the formation of an electrophile. With catenation comes the loss of the total amount of bonded hydrocarbons and an increase in the amount of energy required for bond cleavage due to strain exerted upon the molecule. In simple chemistry, as per valence bond theory, the carbon atom must follow the 4-hydrogen rule, which states that the maximum number of atoms available to bond with carbon is equal to the number of electrons that are attracted into the outer shell of carbon. In terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons, thus has 4 electrons available for covalent or dative bonding.
Hydrocarbons are hydrophobic like lipids. Some hydrocarbons are abundant in the solar system. Lakes of liquid methane and ethane have been found on Titan, Saturn's largest moon, confirmed by the Cassini-Huygens Mission. Hydrocarbons are abundant in nebulae forming polycyclic aromatic hydrocarbon compounds. Hydrocarbons are a primary energy source for current civilizations; the predominant use of hydrocarbons is as a combustible fuel source. In their solid form, hydrocarbons take the form of asphalt. Mixtures of volatile hydrocarbons are now used in preference to the chlorofluorocarbons as a propellant for aerosol sprays, due to chlorofluorocarbons' impact on the ozone layer. Methane and ethane are gaseous at ambient temperatures and cannot be liquefied by pressure alone. Propane is however liquefied, exists in'propane bottles' as a liquid. Butane is so liquefied that it provides a safe, volatile fuel for small pocket lighters. Pentane is a colorless liquid at room temperature used in chemistry and industry as a powerful nearly odorless solvent of waxes and high molecular weight organic compounds, including greases.
Hexane is a used non-polar, non-aromatic solvent, as well as a significant fraction of common gasoline. The C6 through C10 alkanes and isomeric cycloalkanes are the top components of gasoline, jet fuel and specialized industrial solvent mixtures. With the progressive addition of carbon units, the simple non-ring structured hydrocarbons have higher viscosities, lubricating indices, boiling points, solidification temperatures, deeper color. At the opposite extreme from methane lie the heavy tars that remain as the lowest fraction in a crude oil refining retort, they are collected and utilized as roofing comp
The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geodesy, engineering geology, archaeology and geotechnical engineering; this broad base of interests contributes to many research interests within the field. Earth's surface is modified by a combination of surface processes that shape landscapes, geologic processes that cause tectonic uplift and subsidence, shape the coastal geography. Surface processes comprise the action of water, ice and living things on the surface of the Earth, along with chemical reactions that form soils and alter material properties, the stability and rate of change of topography under the force of gravity, other factors, such as human alteration of the landscape.
Many of these factors are mediated by climate. Geologic processes include the uplift of mountain ranges, the growth of volcanoes, isostatic changes in land surface elevation, the formation of deep sedimentary basins where the surface of the Earth drops and is filled with material eroded from other parts of the landscape; the Earth's surface and its topography therefore are an intersection of climatic and biologic action with geologic processes, or alternatively stated, the intersection of the Earth's lithosphere with its hydrosphere and biosphere. The broad-scale topographies of the Earth illustrate this intersection of surface and subsurface action. Mountain belts are uplifted due to geologic processes. Denudation of these high uplifted regions produces sediment, transported and deposited elsewhere within the landscape or off the coast. On progressively smaller scales, similar ideas apply, where individual landforms evolve in response to the balance of additive processes and subtractive processes.
These processes directly affect each other: ice sheets and sediment are all loads that change topography through flexural isostasy. Topography can modify the local climate, for example through orographic precipitation, which in turn modifies the topography by changing the hydrologic regime in which it evolves. Many geomorphologists are interested in the potential for feedbacks between climate and tectonics, mediated by geomorphic processes. In addition to these broad-scale questions, geomorphologists address issues that are more specific and/or more local. Glacial geomorphologists investigate glacial deposits such as moraines and proglacial lakes, as well as glacial erosional features, to build chronologies of both small glaciers and large ice sheets and understand their motions and effects upon the landscape. Fluvial geomorphologists focus on rivers, how they transport sediment, migrate across the landscape, cut into bedrock, respond to environmental and tectonic changes, interact with humans.
Soils geomorphologists investigate soil profiles and chemistry to learn about the history of a particular landscape and understand how climate and rock interact. Other geomorphologists study how hillslopes change. Still others investigate the relationships between geomorphology; because geomorphology is defined to comprise everything related to the surface of the Earth and its modification, it is a broad field with many facets. Geomorphologists use a wide range of techniques in their work; these may include fieldwork and field data collection, the interpretation of remotely sensed data, geochemical analyses, the numerical modelling of the physics of landscapes. Geomorphologists may rely on geochronology, using dating methods to measure the rate of changes to the surface. Terrain measurement techniques are vital to quantitatively describe the form of the Earth's surface, include differential GPS, remotely sensed digital terrain models and laser scanning, to quantify, to generate illustrations and maps.
Practical applications of geomorphology include hazard assessment, river control and stream restoration, coastal protection. Planetary geomorphology studies landforms on other terrestrial planets such as Mars. Indications of effects of wind, glacial, mass wasting, meteor impact and volcanic processes are studied; this effort not only helps better understand the geologic and atmospheric history of those planets but extends geomorphological study of the Earth. Planetary geomorphologists use Earth analogues to aid in their study of surfaces of other planets. Other than some notable exceptions in antiquity, geomorphology is a young science, growing along with interest in other aspects of the earth sciences in the mid-19th century; this section provides a brief outline of some of the major figures and events in its development. The study of landforms and the evolution of the Earth's surface can be dated back to scholars of Classical Greece. Herodotus argued from observations of soils that the Nile delta was growing into the Mediterranean Sea, estimated its age.
Aristotle speculated that due to sediment transport into the sea those seas would fill while the land lowered. He claimed that this would mean that land and water would swap places, whereupon the proc
Bowditch's American Practical Navigator
The American Practical Navigator written by Nathaniel Bowditch, is an encyclopedia of navigation. It serves as a valuable handbook on oceanography and meteorology, contains useful tables and a maritime glossary. In 1867 the copyright and plates were bought by the Hydrographic Office of the United States Navy, as a U. S. Government publication, it is now available free online, it is considered one of America's nautical institutions. The most popular navigational text of the late 18th century was The New Practical Navigator by John Hamilton Moore of the Royal Navy, first published in 1772. To have exact tables to work from, Bowditch recomputed all of Moore's tables, rearranged and expanded the work, he contacted the US publisher of the work, Edmund March Blunt, who asked him to correct and revise the third edition on his fifth voyage. The task was so extensive that Bowditch decided to write his own book, to "put down in the book nothing I can't teach the crew." On that trip, it is said that every man of the crew of 12, including the ship's cook, became competent to take and calculate lunar observations and to plot the correct position of the ship.
The New Practical Navigator was published in 1799, followed by a second edition in 1800. By 1802, when Blunt was ready to publish a third edition, Nathaniel Bowditch and others had corrected so many errors in Moore's work that Blunt decided to publish it as the first edition of a new work, The New American Practical Navigator; the current edition of the American Practical Navigator traces its pedigree to that 1802 edition. Edmund M. Blunt continued to publish the book until 1833; the elder Blunt died in 1862. The next year, 1867, George Blunt sold the copyright to the government for $25,000; the government has published Bowditch since. George Blunt died in 1878. Nathaniel Bowditch continued to correct and revise the book until his death in 1838. Upon his death, the editorial responsibility for The New American Practical Navigator passed to his son, J. Ingersoll Bowditch. Few significant changes were made under him. Editions from 1837 through 1880 are nearly identical in content. Ingersoll Bowditch continued editing the Navigator until George Blunt sold the copyright to the government.
He outlived all of the principals involved in publishing and editing the Navigator, dying in 1889. The U. S. government has published some 52 editions since acquiring the copyright to the book that has come to be known by its original author’s name, "Bowditch". Since the government began production, the book has been known by its year of publishing, instead of by the edition number. After the first major revision, a total overhaul of the book's content completed in 1880 under the direction of Commander Philip H. Cooper, USN, the name was changed to American Practical Navigator. Much of Bowditch’s original content, including his methods for clearing lunar distance observations, were dropped in 1880. After numerous incremental revisions and printings in the period from 1914 to 1944, Bowditch was extensively revised between 1946 and 1958; the present volume, while retaining the basic format of the 1958 version, reorganizes the subjects, deletes obsolete text, adds new material to keep pace with the extensive changes in navigation that have taken place in the electronic age.
The 1995 edition of the American Practical Navigator incorporates extensive changes in organization and format. Recent advances in navigational electronics, communications and other technologies have transformed the way navigation is practiced at sea, it is clear that more changes are forthcoming; the changes to this edition of Bowditch are intended to ensure that this publication remains the premier reference work for practical marine navigation. Concerted efforts were made to return to Nathaniel Bowditch’s original intention "to put down in the book nothing I can’t teach the crew." To this end, many complex formulas and equations have been eliminated, emphasis placed on the capabilities and limitations of various navigation systems and how to use them, instead of explaining complex technical and theoretical details. This edition replaces but does not cancel former editions, which may be retained and consulted as to navigation methods not discussed herein. Current edition is Edition 53, a two-volume, all-digital version released by NGA in 2017.
The Bicentennial Edition incorporated Volume 1 and Volume 2 into a single printed volume, with the goal of putting as much useful information before the navigator as possible in the most understandable and readable format, a single, hard-bound volume. While that edition saw widespread use in civilian and commercial fleets, it sacrificed some data on classical celestial navigation and on advances in satellite and electronic navigation to meet the compressed requirements of the physical form factor. Twenty years with a resurgence in interest on celestial navigation and the large-scale adoption of electronic navigation, NGA returned Pub No. 9 to a two-volume format to encompass the expanded material. To eliminate printing costs, NGA does not intend to produce a physical version of the 2017 edition. Part I Fundamentals, includes an overview of the types and phases of marine navigation and the organizations which support and regulate it, it includes chapters relating to the structure and limitations of nautical charts.
Part II Piloting, emphasizes the practical aspects of navigating a vessel in restricted waters. Part III
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, the rotation of the Earth. Tide tables can be used for any given locale to find the predicted times and amplitude; the predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide, the amphidromic systems of the oceans, the shape of the coastline and near-shore bathymetry. They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience low tides each day. Other locations have a diurnal tide -- one low tide each day. A "mixed tide" – two uneven magnitude tides a day – is a third regular category. Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interval. To make accurate records, tide gauges at fixed stations measure water level over time. Gauges ignore; these data are compared to the reference level called mean sea level.
While tides are the largest source of short-term sea-level fluctuations, sea levels are subject to forces such as wind and barometric pressure changes, resulting in storm surges in shallow seas and near coasts. Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field that varies in time and space is present. For example, the shape of the solid part of the Earth is affected by Earth tide, though this is not as seen as the water tidal movements. Tide changes proceed via the following stages: Sea level rises over several hours, covering the intertidal zone; the water rises to its highest level. Sea level falls over several hours; the water stops reaching low tide. Oscillating currents produced by tides are known as tidal streams; the moment that the tidal current ceases is called slack tide. The tide reverses direction and is said to be turning. Slack water occurs near high water and low water, but there are locations where the moments of slack tide differ from those of high and low water.
Tides are semi-diurnal, or diurnal. The two high waters on a given day are not the same height; the two low waters each day are the higher low water and the lower low water. The daily inequality is not consistent and is small when the Moon is over the Equator. From the highest level to the lowest: Highest astronomical tide – The highest tide which can be predicted to occur. Note that meteorological conditions may add extra height to the HAT. Mean high water springs – The average of the two high tides on the days of spring tides. Mean high water neaps – The average of the two high tides on the days of neap tides. Mean sea level – This is the average sea level; the MSL is constant for any location over a long period. Mean low water neaps – The average of the two low tides on the days of neap tides. Mean low water springs – The average of the two low tides on the days of spring tides. Lowest astronomical tide and Chart Datum – The lowest tide which can be predicted to occur. Modern charts use this as the chart datum.
Note that under certain meteorological conditions the water may fall lower than this meaning that there is less water than shown on charts. Tidal constituents are the net result of multiple influences impacting tidal changes over certain periods of time. Primary constituents include the Earth's rotation, the position of the Moon and Sun relative to the Earth, the Moon's altitude above the Earth's Equator, bathymetry. Variations with periods of less than half a day are called harmonic constituents. Conversely, cycles of days, months, or years are referred to as long period constituents. Tidal forces affect the entire earth. In contrast, the atmosphere is much more fluid and compressible so its surface moves by kilometers, in the sense of the contour level of a particular low pressure in the outer atmosphere. In most locations, the largest constituent is the "principal lunar semi-diurnal" known as the M2 tidal constituent, its period is about 12 hours and 25.2 minutes half a tidal lunar day, the average time separating one lunar zenith from the next, thus is the time required for the Earth to rotate once relative to the Moon.
Simple tide clocks track this constituent. The lunar day is longer than the Earth day because the Moon orbits in the same direction the Earth spins; this is analogous to the minute hand on a watch crossing the hour hand at 12:00 and again at about 1:05½. The Moon orbits the Earth in the same direction as the Earth rotates on its axis, so it takes more than a day—about 24 hours and 50 minutes—for the Moon to return to the same location in the sky. During this time, it has passed overhead once and underfoot once, so in many places the period of strongest tidal forcing is the above-mentioned, about 12 hours and 25 minutes; the moment of highest tide is not when the Moon is nearest to zenith or nadir, but the period of the forcing still determines the time between high tides. Because the gravitational field created by the Moon weakens
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying passengers or goods, or in support of specialized missions, such as defense and fishing. A "ship" was a sailing vessel with at least three square-rigged masts and a full bowsprit. Ships are distinguished from boats, based on size, load capacity, tradition. Ships have been important contributors to human commerce, they have supported the spread of colonization and the slave trade, but have served scientific and humanitarian needs. After the 15th century, new crops that had come from and to the Americas via the European seafarers contributed to the world population growth. Ship transport is responsible for the largest portion of world commerce; as of 2016, there were more than 49,000 merchant ships, totaling 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, 13% were container ships. Ships are larger than boats, but there is no universally accepted distinction between the two.
Ships can remain at sea for longer periods of time than boats. A legal definition of ship from Indian case law is a vessel. A common notion is, but not vice versa. A US Navy rule of thumb is that ships heel towards the outside of a sharp turn, whereas boats heel towards the inside because of the relative location of the center of mass versus the center of buoyancy. American and British 19th Century maritime law distinguished "vessels" from other craft. In the Age of Sail, a full-rigged ship was a sailing vessel with at least three square-rigged masts and a full bowsprit. A number of large vessels are referred to as boats. Submarines are a prime example. Other types of large vessel which are traditionally called boats are Great Lakes freighters and ferryboats. Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters. In most maritime traditions ships have individual names, modern ships may belong to a ship class named after its first ship.
In the northern parts of Europe and America a ship is traditionally referred to with a female grammatical gender, represented in English with the pronoun "she" if named after a man. This is not universal usage and some English language journalistic style guides advise using "it" as referring to ships with female pronouns can be seen as offensive and outdated. In many documents the ship name is introduced with a ship prefix being an abbreviation of the ship class, for example "MS" or "SV", making it easier to distinguish a ship name from other individual names in a text; the first known vessels could not be described as ships. The first navigators began to use animal skins or woven fabrics as sails. Affixed to the top of a pole set upright in a boat, these sails gave early ships range; this allowed men to explore allowing for the settlement of Oceania for example. By around 3000 BC, Ancient Egyptians knew, they used woven straps to lash the planks together, reeds or grass stuffed between the planks helped to seal the seams.
The Greek historian and geographer Agatharchides had documented ship-faring among the early Egyptians: "During the prosperous period of the Old Kingdom, between the 30th and 25th centuries BC, the river-routes were kept in order, Egyptian ships sailed the Red Sea as far as the myrrh-country." Sneferu's ancient cedar wood ship Praise of the Two Lands is the first reference recorded to a ship being referred to by name. The ancient Egyptians were at ease building sailboats. A remarkable example of their shipbuilding skills was the Khufu ship, a vessel 143 feet in length entombed at the foot of the Great Pyramid of Giza around 2500 BC and found intact in 1954, it is known that ancient Nubia/Axum traded with India, there is evidence that ships from Northeast Africa may have sailed back and forth between India/Sri Lanka and Nubia trading goods and to Persia and Rome. Aksum was known by the Greeks for having seaports for ships from Yemen. Elsewhere in Northeast Africa, the Periplus of the Red Sea reports that Somalis, through their northern ports such as Zeila and Berbera, were trading frankincense and other items with the inhabitants of the Arabian Peninsula well before the arrival of Islam as well as with Roman-controlled Egypt.
A panel found at Mohenjodaro depicted a sailing craft. Vessels were of many types; this treatise gives a technical exposition on the techniques of shipbuilding. It sets forth minute details about the various types of ships, their sizes, the materials from which they were built; the Yukti Kalpa Taru sums up in a condensed form all the available information. The Yukti Kalpa Taru gives sufficient information and dates to prove that, in ancient times, Indian shipbuilders had a good knowledge of the materials which were used in building ships. In addition to describing the qualities of the different types of wood and their suitability for shipbuilding, the Yukti Kalpa Taru gives an elaborate classification of ships based on their size; the oldest discovered sea faring hulled boat is the Late Bronze Age Uluburun shipwreck off the coast of Turkey, dating back to 1300 BC. The Phoenicians, the first to sail around