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258_17 | 1983 - Museum Boymans - Van Beuningen - Rotterdam - Netherlands - Group
1982 - New York - Institute of Contemporary Arts - London - England - Group |
258_18 | Collections
Rammellzee's work is held in the following public collection:
Museum of Modern Art, New York: one 12-inch vinyl record (Beat Bop) and a series of ten drawings titled Alphabet, undated
Museum of Graffiti, Miami
Discography
Studio albums
Singles & EPs
References
External links
Artist biography at Magical-Secrets.com
Excerpts from Rammellzee's thesis Iconic Treatise Gothic Futurism
Interview with Rammellzee
Video Interview with Guerilla Art
Red Bull Music and Culture Video Profile "RAMMELLZEE: It's Not Who But What"
Art gallery |
258_19 | 1960 births
2010 deaths
American graffiti artists
Rappers from New York City
20th-century American painters
American male painters
American people of Italian descent
21st-century American painters
Artists from New York City
Mass media theorists
People from Far Rockaway, Queens
Postmodern artists
20th-century American printmakers
African-American contemporary artists
American contemporary painters
African-American male models
African-American painters
African-American printmakers
20th-century African-American male singers
21st-century African-American artists |
259_0 | Metal-ligand cooperativity (MLC) is a mode of reactivity in which a metal and ligand of a complex are both involved in the bond breaking or bond formation of a substrate during the course of a reaction. This ligand is an actor ligand rather than a spectator, and the reaction is generally only deemed to contain MLC if the actor ligand is doing more than leaving to provide an open coordination site. MLC is also referred to as "metal-ligand bifunctional catalysis." Note that MLC is not to be confused with cooperative binding. |
259_1 | The earliest reported metal-ligand cooperativity was from the Fujiwara group in the 1950s, in which they reported formation of stilbene from styrene and arenes using a palladium chloride catalyst. Shvo's catalyst was developed for one of the earliest uses of ketone hydrogenation by an outer-sphere mechanism. Noyori has developed many chiral catalysts for asymmetric hydrogenation. Transfer hydrogenation, one of the most commonly used applications of MLC, is employed broadly in industry for large scale Noyori-type reductions.
Modes of Metal-Ligand Cooperativity
There are a variety of modes in which this cooperativity has been demonstrated. Four primary modes are generally accepted under MLC: the ligand can (1) act with Lewis acidity, (2) act with Lewis basicity, (3) play a role in aromatization and dearomatization, or (4) be redox non-innocent. |
259_2 | The ligand can act as a Lewis acid and accept electrons from an incoming substrate as it binds to the metal, as in employed in dehydrogenation catalysis. Conversely, the ligand can be Lewis basic and bind the substrate; this Lewis basicity is most frequently seen in hydrogenation catalysis.
The aromatization and dearomatization of a ligand can serve to facilitate a reaction. As shown in the figure, a ligand can be dearomatized by a base and thus activated toward cleaving a C-H or H-H bond and be subsequently rearomatized during substrate bond cleavage. NHC ligands and other pincer ligands are frequently employed in this mode of MLC. In some reports, with bidentate ligands, ligand dearomatization is not observed when the complex is treated with base but rather a complex with a formal metal-carbon bond is observed (that then acts as a Lewis basic ligand). |
259_3 | The ligand can also be redox non-innocent to facilitate reactions that the metal would otherwise be unable to activate. The ligand can act as an electron reservoir, which is enabled when ligands contain frontier orbitals of suitable energy to participate in the redox event themselves, and can accept or donate electrons during the course of the reaction, allowing the metal to modulate its oxidation state. This allows metals which normally only participate in one electron regimes to be used in two electron regimes with a redox non-innocent ligand to store electrons during the reaction. Dithiolate ligands have been used extensively as one electron redox active ligands in metal complexes. For example, dithiolates have been demonstrated to allow for the selective and reversible reduction of ethylene in the presence H2, CO, and H2S. This has applications in the purification of ethylene gas streams, in which ethylene can be reduced electrochemically by a dithiolate, selectively removed from |
259_4 | the impurities in the stream, and then reversibly desaturated. |
259_5 | Electrochemical metal-ligand cooperativity in redox reactions allows for ease of tuning the potential of the ligands to avoid off-target reactivity.
There are a number of other ligand modes of reactivity which are sometimes classified under MLC. This includes reactions in which the ligand accepts or loses a proton, though not directly from or to the substrate. Ligands can also be used to form stabilizing H-bonds, which can be applied in molecular recognition catalysis. Ligands can also be designed to be photoresponsive, with applications in molecular switches. Ligands may also be considered to be involved in MLC while acting only in the second coordination sphere (not directly bound to the metal) but acting as a proton shuttle. Frustrated Lewis pairs, in which an ion pair of the type [R3B-H]−[H-Ar3]+ transfer a hydride and proton are also sometimes classified under MLC. |
259_6 | Mechanism of Hydrogenations with Metal-Ligand Cooperativity |
259_7 | MLC is most frequently used in hydrogenations, with many applications in asymmetric catalysis and in process scale production of chemicals. In a hydrogenation, there is a transfer of a hydride and a hydrogen to a substrate. Typical substrates include aldehydes, ketones, and imines. As this is a common use for MLC, it is instructive in understanding the mechanism of metal-ligand cooperativity. MLC occurs through an outer sphere mechanism. An outer sphere mechanism does not necessitate that the metal undergo oxidative addition or reductive elimination. Thus, H2 is not added across the metal, but rather across the metal and a ligand; alternatively, the metal complexes are preformed to contain a hydride ligand as well as a ligand with a hydrogen alpha to the metal. Thus, the hydride and hydrogen are adjacent to one another, facilitating the transfer to the substrate; this transfer occurs without the substrate ever binding to the metal itself. Though amine is by far the most used ligand in |
259_8 | cooperativity, other actor ligands include alkoxides and thiols. |
259_9 | In contrast, in an inner sphere mechanism, the substrate will be inserted into the metal and reaction with hydrogen will then afford the hydrogenated product. This mechanism does not employ MLC. The differentiation between an outer sphere mechanism relying on MLC and an inner sphere mechanism is exemplified by cobalt hydrogenation with an amine pincer ligand. In the outer sphere mechanism, the hydrogen on the pincer ligand is added into the ketone along with a hydride ligand on the metal. It is worth noting that there is debate over the concertedness of the transition state of this outer sphere hydrogenation step, and different reactions and catalysts may be either concerted or stepwise, and in some scenarios there may be multiple pathways at play. In comparison to the ketone hydrogenation, an olefin undergoes an inner sphere mechanism under the same reaction conditions, in which the olefin inserts directly into the metal. These mechanistic differences between the ketone and olefin |
259_10 | are corroborated by the observation that the ketone hydrogenation will not occur with an N-Me pincer ligand, and the olefin hydrogenation will proceed with the N-Me ligand, suggesting the ketone requires the presence of the N-H bond while the olefin does not. |
259_11 | Common Ligands |
259_12 | MLC is most broadly used with M-NH systems. Nyori and others have developed an extensive library of diamine ligands which serve in hydrogenation reactions, following the general outer sphere mechanism illustrated above. These systems are typically ruthenium complexes containing phosphine ligands as the spectator ligands. Many of these diphosphine ligands, such as BINAP, contain arene rings and impart chirality from atropisomerism; the rigidity of the phosphene ligands can impart chirality on prochiral substrates with high fidelity, allowing for asymmetric hydrogenation. Reactivity of metal complexes used in MLC can be tuned greatly by the use of different diphosphine spectator ligands. |
259_13 | M-OH metal ligand systems have application in MLC. Shvo's catalyst was one of the earliest complexes developed for ketone and aldehyde reductions to alcohols. The ruthenium complex (1), upon heating, dissociates into a 18 electron complex (2) and a 16 electron complex (3), the former of which is catalytically active. The hydroxy group on the cyclopentadienyl is the actor ligand, donating a hydrogen in an outer sphere mechanism. Bäckvall has developed use for Shvo's catalyst in the dynamic kinetic resolution of alcohols with lipases. |
259_14 | Bergman and coworkers developed a sulfur ligand for activation of H-H as well as Si-H bonds. A titanium sulfide complex binds H2 across the titanium and sulfur, yielding a hydride and thiol ligand. A similar mode of reactivity is seen with H-Si bonds, in which the sulfide forms a bond with the silicon, and the titanium accepts the hydride. The use of sulfur ligands in MHC has continued to expand since Bergman's early work in the field. Iridium and rhenium complexes with bridging sulfides have been demonstrated to heterolytically cleave H2.
Metal boron complexes have also been demonstrated to be useful in activating H2. These ligands are less developed for the purpose of MLC, and commonly suffer from off target alkyl and aryl migration from the boron ligand to other ligands or substrates which disrupts the catalytic cycle
References
Hydrogenation |
260_0 | The cuisine of Philadelphia was shaped largely by the city's mixture of ethnicities, available foodstuffs and history. Certain foods have become associated with the city.
Invented in Philadelphia in the 1930s, the cheesesteak is the most well known, and soft pretzels have long been a major part of Philadelphia culture.
The late 19th and early 20th centuries saw the creation of two Philadelphia landmarks, the Reading Terminal Market and Italian Market. After a dismal restaurant scene during the post-war era of the 20th century, the 1970s brought a restaurant renaissance that has continued into the 21st century.
Many foods and drinks associated with Philadelphia can also commonly be linked with the Pennsylvania Dutch cuisine and Italian-American cuisine. |
260_1 | Innovations
Philadelphia's large immigrant population has contributed to a large mixture of tastes to mingle and develop. Many types of foods have been created in or near Philadelphia or have strong associations with the city. In the 20th century, Philadelphia's foods included the cheesesteak, stromboli, hoagie, soft pretzel, water ice and soda.
The cheesesteak is a sandwich traditionally made with sliced beef and melted cheese on an Italian roll. In the 1930s, the phenomenon as a steak sandwich began when hot dog vendor brothers Pat Olivieri and Harry Olivieri put grilled beef on a hot dog bun and gave it to a taxi driver. Later, after Pat and Harry had started selling the sandwich on Italian rolls, the cheesesteak was affixed in the local culture when one of their cooks put melted cheese on the sandwich. |
260_2 | Originally, the cheese was melted in a separate container to accommodate their large clientele who followed kosher rules (thereby not mixing dairy and meat). Today, cheese choices in Philadelphia eateries are virtually limited to American, Provolone, or Cheez Whiz. The latter is especially popular in those places that prominently carry it.
The hoagie is another sandwich that is said to have been invented in Philadelphia, undoubtedly of origin in Italian-American cuisine. It has been asserted that Italians working at the World War I era shipyard in Philadelphia, known as Hog Island where emergency shipping was produced for the war effort, introduced the sandwich, by putting various sliced meats, cheeses, and lettuce between two slices of Italian bread. This became known as the "Hog Island" sandwich; hence, the "hoagie".
Declared the official sandwich of Philadelphia in 1992, the hoagie is a sandwich made of meat and cheese with lettuce, tomatoes, and onions on an Italian roll. |
260_3 | Another Italian roll sandwich popularized in Philadelphia by Italian immigrants is the roast pork Italian, or Italian roast pork sandwich, a variation of the Italian street food dish known as porchetta. The sandwich consists of sliced roast pork with broccoli rabe or spinach and provolone cheese.
Philadelphia Pepper Pot, a soup of tripe, meat, vegetables, is claimed to have been created during the American Revolutionary War and named after the home city of its creator.
Snapper soup, a thick brown turtle soup served with sherry, is a Philadelphia delicacy, generally found in area bars and seafood restaurants. In many places, it is served with oyster crackers (such as OTC Crackers, OTC being an abbreviation for "Original Trenton Cracker") and horseradish. |
260_4 | The snack item commonly associated with Philadelphia, but not invented there, is the soft pretzel. The soft pretzel dates back to 7th-century France and was brought over to the Philadelphia area by the Pennsylvania Dutch. Pretzels were sold in Philadelphia by numerous vendors on street corners. Federal Pretzel Baking Company defined the soft pretzel for most Philadelphians during the 1900s by first applying mass production and distribution to a distinctive baked flavored family recipe.
Another snack associated with Philadelphia is Irish potato candy. The candies have a coconut cream inside (generally made from some blend of coconut, confectioner's sugar, vanilla, and cream or cream cheese) and are rolled in cinnamon on the outside, resulting in an appearance reminiscent of small potatoes. The treats are about the size of a large marble and are especially popular around St. Patrick's Day. |
260_5 | Oh Ryan's of Boothwyn, Pennsylvania, claims to be the largest distributor of Irish Potatoes, shipping about 80,000 pounds to major chains and smaller candy stores, mostly in the Philadelphia area.
Water ice, known as Italian ice in other Northeastern US cities, is similarly associated with Philadelphia, brought to Philadelphia by Italian immigrants. Water ice likely derives from semi-frozen desserts originating in Italy, specifically granita. |
260_6 | The Philadelphia metropolitan area (including Delaware Valley, South Jersey, Southeastern Pennsylvania) is the only region of the United States to refer to the dessert as "water ice"; in other areas, such as New York City, water ice is called "Italian ice". However, despite the overlap and near synonymity between the two terms, water ice has been described as a specific type of Italian ice originating in Philadelphia, or a "variation on the more broadly-accepted Italian ice." Certain stands like South Philadelphia's "Pop's" or "Italiano's" became similar products later franchised into new markets like "Rita's Water Ice".
As with New York City and Chicago, Philadelphia has its own regional variant of hot dog known as the Texas Tommy, originating right outside Philadelphia in Pottstown, Pennsylvania before spreading throughout the Delaware Valley region and South Jersey. The Texas Tommy hot dog is defined by its use of cheese (usually cheddar cheese) and bacon as toppings. |
260_7 | Some variations of the Texas Tommy use other forms of cheese, replacing the cheddar with the Cheez-Whiz found on cheesesteaks. The bacon and cheese are often wrapped around the hot dog, and the hot dog may be cooked using a variety of methods, such as deep frying, barbecuing, or grilling. Condiments such as mustard, ketchup, or relish may be used in addition to the bacon and cheese.
Chili is also sometimes added to the Texas Tommy, making the dish resemble more closely a Texas Wiener or chili dog with bacon and cheese.
Some types of soda that rose to popularity in Philadelphia include Hires Root Beer, Franks Beverages' unique Black Cherry Wishniak or Vanilla Cream, and Levis Champ Cherry.
Restaurants and markets |
260_8 | In early Philadelphia history the city's eating scene was dominated by taverns. By 1752, Philadelphia had 120 licensed taverns and numerous illegal taverns. The taverns ranged for all types of people and class from illegal grog shops on the waterfront that sailors frequented to the upper class taverns that members of city government enjoyed.
Taverns such as the London Coffee House, the Blue Anchor, Tun Tavern and John Biddle's Indian King were regular meeting places for the political and business leaders of the city. The City Tavern is a replica of a historic 18th-century building located at 138 South 2nd Street and is part of Independence National Historical Park. The tavern offers authentic 18th-century recipes, served in seven period dining rooms, three wine cellar rooms and an outdoor garden.
McGillin's Olde Ale House, located on Drury Street in Center City, is the oldest continuously operated tavern in the city, and has become a well-knownplace for celeb-spotting. |
260_9 | Popular restaurants during the early 19th century included the United States Hotel and Parkinson's on Chestnut Street and Joseph Head Mansion's House on Spruce Street. One of the most significant restaurateurs and caterers at this time was M. Latouche, an expert in French cuisine, whose restaurant offered expensive food and choice wine.
Toward the end of the 19th century, the large number of Italian immigrants in South Philadelphia led to the creation of the Italian Market. The market, which runs along part of south 9th Street, includes numerous types of food vendors along with other shops, although today it is mostly made up of non-Italian merchants. |
260_10 | Another market, the Reading Terminal Market, opened in 1892. Created to replace the markets displaced by the construction of the Reading Terminal on Market Street in Center City, Reading Terminal Market has over 80 merchants and is a popular tourist attraction. In 1902, Joseph Horn and Frank Hardart opened the first automat in the U.S. at 818 Chestnut Street, now a retail store. The original Automat is now part of the Smithsonian Institution.
In the 1950s and 1960s, the restaurant scene was in decline. The city saw a large emigration into the suburbs, and fine dining could be found mainly in private clubs and dinner parties. |
260_11 | But as the city started to rebound in the 1970s, Philadelphia saw a restaurant renaissance. For instance, in 1970 Georges Perrier and Peter Von Starck founded French restaurant Le Panetiere. After a year, the two split, with Von Starck taking the Panetiere name to a different location. Perrier opened Le Bec-Fin at 13th & Spruce Street, then later at 1523 Walnut Street, which quickly became one of Philadelphia's most renowned restaurants. Another popular example is H.A Winston & Co., which evolved into a chain of restaurants located throughout the region.
The years following saw many new fine dining places open, including Four Seasons' Fountain Restaurant in 1983. Along with the up-scale restaurants, numerous ethnic and fast-food restaurants opened throughout the city. |
260_12 | The 1970s also saw the rise of street vendors. The vendors, building off the well-established tradition of chestnut and pretzel vendors, began selling numerous foods, especially hot dogs, cheesesteaks, and breakfast sandwiches. By taking up sidewalk space and possibly business, the vendors annoyed established stores which eventually led to numerous legal battles over ordinances which placed restrictions on vendors.
The issue was surrounded by race and class overtones, but vendors have since become commonplace and even nationally renowned for serving quality food.
A wide variety of eateries now thrive in Philadelphia. The city has a growing reputation for culinary excellence, and many of the city's chefs have been honored with nominations for James Beard Awards |
260_13 | Prolific local restaurateurs like Stephen Starr's STARR Restaurants and Iron Chef Jose Garces's Garces Restaurant Group operate restaurants that coexist with small chef-owned BYOBs. Major dining locations include Rittenhouse Square, Old City, Chinatown, Manayunk, East Passyunk Avenue and Fishtown.
A variety of cuisine popular with Philadelphians today include Italian, Mediterranean, Chinese, Japanese, steakhouses, French, gastropub fare, tapas, diners, delis, and pizzerias.
In September 2006, a smoking ban went into effect for Philadelphia bars and restaurants. The ban, which exempts private clubs, hotels, specialty smoking shops, and waiver-eligible bars that serve little food, had a troubled start and went unenforced until January 2007.
Just a month later Philadelphia City Council passed a ban on trans fat in restaurants, effective September 2, 2007. Other health reforms have been introduced by the Get Healthy Philly Initiative.
Other foods with Philadelphia historical roots |
260_14 | Cheese sauce—gooey, orange, dairy condiment carried by many street vendors. In general, Philadelphians often add cheese sauce to inexpensive food items, such as French fries and pretzels. The vast majority of cheese sauce served on Philadelphia foods is the national brand Cheez Whiz.
Funnel cake—associated with the Pennsylvania Dutch, made by pouring batter into hot cooking oil in a circular pattern and deep frying the overlapping mass until golden-brown; extremely popular in the Philadelphia area.
German butter cake—very rich type of pound cake with a buttery, pudding-like center, not to be confused with the traditional butter cake or the St. Louis version. Also called Philadelphia Butter Cake.
Good & Plenty—popular licorice pastille candy created in 1893.
Herr's—Philadelphia-area snack brand, noted for potato chips and other snack foods
Peanut Chews—popular candy produced in Philadelphia since 1917 |
260_15 | Pork roll—although developed and mostly produced in Trenton (on the border between the Philadelphia and New York spheres of influence) and mostly associated with New Jersey culinary traditions, pork roll is widely available in the Philadelphia area and well-incorporated into Philadelphian cuisine.
Roast pork sandwich—usually served on an Italian roll and often with broccoli rabe instead of spinach and most traditionally with sharp provolone; a staple of South Philadelphia cuisine.
Scrapple—processed meat loaf made of pork scraps and trimmings combined with cornmeal and flour, is a Pennsylvanian breakfast food. |
260_16 | Soda—in the early 19th century, Dr. Philip Syng Physick and John Hart of Philadelphia invented carbonated water in an attempt to simulate water from natural springs. In 1807, Philadelphian pharmacist Townsend Speakman sold fruit juice and carbonated water, inventing the first soft drink. In 1875, Charles Elmer Hires invented root beer by mixing sarsaparilla, sassafras, wild cherry, wintergreen, ginger, and alcohol. He sold it at his drug store in Philadelphia.
Whoopie pie—also associated with the Pennsylvania Dutch, it is made of two round mound-shaped pieces of chocolate cake, or sometimes pumpkin or gingerbread cake, with a sweet, creamy filling or frosting sandwiched between them. Also popular in New England.
Spiced wafers—type of cookie traditionally sold in the autumn. |
260_17 | Stromboli—reported to have originated in 1950 in Essington, just outside Philadelphia. It is a type of turnover made with Italian bread dough filled with various kinds of cheese, Italian charcuterie or vegetables. Panzarotti is a trademark for a type of deep-fried stromboli, particularly associated with Philadelphia's South Jersey suburbs.
Tastykake—most well-known snack brand native to Philadelphia. Since 1914, the Tasty Baking Company has provided the region with its line of pre-packaged baked goods; best-known varieties include Krimpets, cupcakes, Kandy Kakes (wafer-sized chocolate and peanut butter cakes), and Tasty Pies.
Tomato pie—essentially a cheeseless pizza two-feet by three-feet in size, with extra oregano. Tomato pie is normally served cold or at room temperature. It is more often found in the Northeast section of Philadelphia and at bakeries in South Philadelphia with variations found in Trenton, New Jersey and other suburban localities. |
260_18 | Texas Tommy—grilled, split hot dog with bacon and cheese; a common hot dog dish in Philadelphia.
Water ice—a version of Italian ice that is popular in Philadelphia and the Delaware Valley. It is sold to order at specific shops and pre-packaged in grocery stores. |
260_19 | Alcoholic beverages
Beer was brewed by English colonial inhabitants of Philadelphia since the city's founding in 1682, and later by German immigrants that settled the city's countryside. Because of this, the city is strongly identified with both English-style beer (particularly porter, a variety that was virtually synonymous with Philadelphia during the American Revolutionary period) and German-style beer (such as lager), which eclipsed the English style near the end of the 19th century.
In the industry's heyday before Prohibition, more than 90 breweries operated in city limits, with another 100 located in the greater metropolitan area. A neighborhood in the city is still called Brewerytown, owing to the concentration of breweries in the area during this time. The last of the city's most successful brewers, such as the Henry F. Ortlieb Brewing Company and the Christian Schmidt Brewing Company, shut down in the 1980s. |
260_20 | The beer most associated with Philadelphia is Yuengling lager, brewed in nearby Pottsville, Pennsylvania and often referred to as simply "Lager" by Philadelphians and people in the Delaware Valley and South Jersey.
Recently, however, a number of highly regarded micro-breweries and brewpubs appeared in and around the city in the 1990s and 2000s, such as Victory, Yards and PBC, reviving the city's dormant brewing industry. (For more information, see Breweries in Philadelphia.) In 2011, Philadelphia was ranked as one of the 14 best beer cities in the world by Frommer's, and the city's annual beer week is among its most popular food-centric civic events.
Other notable Delaware Valley microbreweries and brewpubs include Iron Hill Breweries and the award-winning Sly Fox Brewery.
The distillation of spirits in Philadelphia has a long history, but the industry has sat idle for several decades. |
260_21 | One of the largest manufacturing complexes in the city, spanning 40 acres, was owned by Publicker Industries, which produced chemicals, industrial alcohols and spirits in South Philadelphia. Its Continental Distilling Company arm produced Old Hickory bourbon, Inver House Scotch and Skol vodka, among many other liquors, before the company abandoned the site in 1986.
The oldest producer of cordials and liqueurs in the U.S., Charles Jacquin et Cie, remains in operation in the city's Kensington neighborhood; the company is best known for its Pravda vodka, Jacquin's family of liqueurs and Original Bartenders Cocktails brand, well as its introduction of Chambord (sold to Brown-Forman in 2006), Creme Yvette, St-Germain and Domaine de Canton to the U.S. market. |
260_22 | More recently, Philadelphia Distilling opened in 2005 in the city's Fishtown neighborhood; it is the first craft distillery to open in Pennsylvania since before Prohibition, and produces Bluecoat American Dry Gin, Vieux Carré Absinthe Supérieure, Penn 1681 vodka, XXX Shine corn whiskey and The Bay, a vodka seasoned with Chesapeake Bay seasoning.
See also
Cuisine of the Pennsylvania Dutch
Cuisine of the Thirteen Colonies
Cuisine of New Jersey
Cuisine of Allentown, Pennsylvania
References |
261_0 | A double layer (DL, also called an electrical double layer, EDL) is a structure that appears on the surface of an object when it is exposed to a fluid. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. The DL refers to two parallel layers of charge surrounding the object. The first layer, the surface charge (either positive or negative), consists of ions adsorbed onto the object due to chemical interactions. The second layer is composed of ions attracted to the surface charge via the Coulomb force, electrically screening the first layer. This second layer is loosely associated with the object. It is made of free ions that move in the fluid under the influence of electric attraction and thermal motion rather than being firmly anchored. It is thus called the "diffuse layer". |
261_1 | (-> this description of DL is not right, at least concerning the electrode/electrolyte interface. Here DL refers to charge separation at the interface with the electrode (which typically is a metal) possessing negative charge and the electrolyte positive charge. The two layers (one electronic the other ionic) are separated by some molecular distance. The two layers mentioned in above description are all at the electrolyte side (the Gouy-Chapman model). |
261_2 | Interfacial DLs are most apparent in systems with a large surface area to volume ratio, such as a colloid or porous bodies with particles or pores (respectively) on the scale of micrometres to nanometres. However, DLs are important to other phenomena, such as the electrochemical behaviour of electrodes.
DLs play a fundamental role in many everyday substances. For instance, homogenized milk exists only because fat droplets are covered with a DL that prevents their coagulation into butter. DLs exist in practically all heterogeneous fluid-based systems, such as blood, paint, ink and ceramic and cement slurry.
The DL is closely related to electrokinetic phenomena and electroacoustic phenomena.
Development of the (interfacial) double layer
Helmholtz |
261_3 | When an electronic conductor is brought in contact with a solid or liquid ionic conductor (electrolyte), a common boundary (interface) among the two phases appears. Hermann von Helmholtz was the first to realize that charged electrodes immersed in electrolyte solutions repel the co-ions of the charge while attracting counterions to their surfaces. Two layers of opposite polarity form at the interface between electrode and electrolyte. In 1853 he showed that an electrical double layer (DL) is essentially a molecular dielectric and stores charge electrostatically. Below the electrolyte's decomposition voltage, the stored charge is linearly dependent on the voltage applied.
This early model predicted a constant differential capacitance independent from the charge density depending on the dielectric constant of the electrolyte solvent and the thickness of the double-layer. |
261_4 | This model, with a good foundation for the description of the interface, does not consider important factors including diffusion/mixing of ions in solution, the possibility of adsorption onto the surface, and the interaction between solvent dipole moments and the electrode.
Gouy–Chapman
Louis Georges Gouy in 1910 and David Leonard Chapman in 1913 both observed that capacitance was not a constant and that it depended on the applied potential and the ionic concentration. The "Gouy–Chapman model" made significant improvements by introducing a diffuse model of the DL. In this model, the charge distribution of ions as a function of distance from the metal surface allows Maxwell–Boltzmann statistics to be applied. Thus the electric potential decreases exponentially away from the surface of the fluid bulk. |
261_5 | Stern
The Gouy-Chapman model fails for highly charged DLs. In 1924, Otto Stern suggested combining the Helmholtz model with the Gouy-Chapman model: in Stern's model, some ions adhere to the electrode as suggested by Helmholtz, giving an internal Stern layer, while some form a Gouy-Chapman diffuse layer.
The Stern layer accounts for ions' finite size and consequently an ion's closest approach to the electrode is on the order of the ionic radius. The Stern model has its own limitations, namely that it effectively treats ions as point charges, assumes all significant interactions in the diffuse layer are Coulombic, assumes dielectric permittivity to be constant throughout the double layer, and that fluid viscosity is constant plane. |
261_6 | Grahame
D. C. Grahame modified the Stern model in 1947. He proposed that some ionic or uncharged species can penetrate the Stern layer, although the closest approach to the electrode is normally occupied by solvent molecules. This could occur if ions lose their solvation shell as they approach the electrode. He called ions in direct contact with the electrode "specifically adsorbed ions". This model proposed the existence of three regions. The inner Helmholtz plane (IHP) passes through the centres of the specifically adsorbed ions. The outer Helmholtz plane (OHP) passes through the centres of solvated ions at the distance of their closest approach to the electrode. Finally the diffuse layer is the region beyond the OHP. |
261_7 | Bockris/Devanathan/Müllen (BDM)
In 1963 J. O'M. Bockris, M. A. V. Devanathan and Klaus Müller proposed the BDM model of the double-layer that included the action of the solvent in the interface. They suggested that the attached molecules of the solvent, such as water, would have a fixed alignment to the electrode surface. This first layer of solvent molecules displays a strong orientation to the electric field depending on the charge. This orientation has great influence on the permittivity of the solvent that varies with field strength. The IHP passes through the centers of these molecules. Specifically adsorbed, partially solvated ions appear in this layer. The solvated ions of the electrolyte are outside the IHP. Through the centers of these ions pass the OHP. The diffuse layer is the region beyond the OHP. |
261_8 | Trasatti/Buzzanca
Further research with double layers on ruthenium dioxide films in 1971 by Sergio Trasatti and Giovanni Buzzanca demonstrated that the electrochemical behavior of these electrodes at low voltages with specific adsorbed ions was like that of capacitors. The specific adsorption of the ions in this region of potential could also involve a partial charge transfer between the ion and the electrode. It was the first step towards understanding pseudocapacitance.
Conway
Between 1975 and 1980 Brian Evans Conway conducted extensive fundamental and development work on ruthenium oxide electrochemical capacitors. In 1991 he described the difference between 'Supercapacitor' and 'Battery' behavior in electrochemical energy storage. In 1999 he coined the term supercapacitor to explain the increased capacitance by surface redox reactions with faradaic charge transfer between electrodes and ions. |
261_9 | His "supercapacitor" stored electrical charge partially in the Helmholtz double-layer and partially as the result of faradaic reactions with "pseudocapacitance" charge transfer of electrons and protons between electrode and electrolyte. The working mechanisms of pseudocapacitors are redox reactions, intercalation and electrosorption.
Marcus |
261_10 | The physical and mathematical basics of electron charge transfer absent chemical bonds leading to pseudocapacitance was developed by Rudolph A. Marcus. Marcus Theory explains the rates of electron transfer reactions—the rate at which an electron can move from one chemical species to another. It was originally formulated to address outer sphere electron transfer reactions, in which two chemical species change only in their charge, with an electron jumping. For redox reactions without making or breaking bonds, Marcus theory takes the place of Henry Eyring's transition state theory which was derived for reactions with structural changes. Marcus received the Nobel Prize in Chemistry in 1992 for this theory. |
261_11 | Mathematical description
There are detailed descriptions of the interfacial DL in many books on colloid and interface science and microscale fluid transport. There is also a recent IUPAC technical report on the subject of interfacial double layer and related electrokinetic phenomena. |
261_12 | As stated by Lyklema, "...the reason for the formation of a "relaxed" ("equilibrium") double layer is the non-electric affinity of charge-determining ions for a surface..." This process leads to the buildup of an electric surface charge, expressed usually in C/m2. This surface charge creates an electrostatic field that then affects the ions in the bulk of the liquid. This electrostatic field, in combination with the thermal motion of the ions, creates a counter charge, and thus screens the electric surface charge. The net electric charge in this screening diffuse layer is equal in magnitude to the net surface charge, but has the opposite polarity. As a result, the complete structure is electrically neutral. |
261_13 | The diffuse layer, or at least part of it, can move under the influence of tangential stress. There is a conventionally introduced slipping plane that separates mobile fluid from fluid that remains attached to the surface. Electric potential at this plane is called electrokinetic potential or zeta potential (also denoted as ζ-potential).
The electric potential on the external boundary of the Stern layer versus the bulk electrolyte is referred to as Stern potential. Electric potential difference between the fluid bulk and the surface is called the electric surface potential. |
261_14 | Usually zeta potential is used for estimating the degree of DL charge. A characteristic value of this electric potential in the DL is 25 mV with a maximum value around 100 mV (up to several volts on electrodes). The chemical composition of the sample at which the ζ-potential is 0 is called the point of zero charge or the iso-electric point. It is usually determined by the solution pH value, since protons and hydroxyl ions are the charge-determining ions for most surfaces.
Zeta potential can be measured using electrophoresis, electroacoustic phenomena, streaming potential, and electroosmotic flow.
The characteristic thickness of the DL is the Debye length, κ−1. It is reciprocally proportional to the square root of the ion concentration C. In aqueous solutions it is typically on the scale of a few nanometers and the thickness decreases with increasing concentration of the electrolyte. |
261_15 | The electric field strength inside the DL can be anywhere from zero to over 109 V/m. These steep electric potential gradients are the reason for the importance of the DLs.
The theory for a flat surface and a symmetrical electrolyte is usually referred to as the Gouy-Chapman theory. It yields a simple relationship between electric charge in the diffuse layer σd and the Stern potential Ψd:
There is no general analytical solution for mixed electrolytes, curved surfaces or even spherical particles. There is an asymptotic solution for spherical particles with low charged DLs. In the case when electric potential over DL is less than 25 mV, the so-called Debye-Huckel approximation holds. It yields the following expression for electric potential Ψ in the spherical DL as a function of the distance r from the particle center:
There are several asymptotic models which play important roles in theoretical developments associated with the interfacial DL. |
261_16 | The first one is "thin DL". This model assumes that DL is much thinner than the colloidal particle or capillary radius. This restricts the value of the Debye length and particle radius as following:
This model offers tremendous simplifications for many subsequent applications. Theory of electrophoresis is just one example. The theory of electroacoustic phenomena is another example.
The thin DL model is valid for most aqueous systems because the Debye length is only a few nanometers in such cases. It breaks down only for nano-colloids in solution with ionic strengths close to water.
The opposing "thick DL" model assumes that the Debye length is larger than particle radius:
This model can be useful for some nano-colloids and non-polar fluids, where the Debye length is much larger.
The last model introduces "overlapped DLs". This is important in concentrated dispersions and emulsions when distances between particles become comparable with the Debye length. |
261_17 | Electrical double layers
The electrical double layer (EDL) is the result of the variation of electric potential near a surface, and has a significant influence on the behaviour of colloids and other surfaces in contact with solutions or solid-state fast ion conductors.
The primary difference between a double layer on an electrode and one on an interface is the mechanisms of surface charge formation. With an electrode, it is possible to regulate the surface charge by applying an external electric potential. This application, however, is impossible in colloidal and porous double layers, because for colloidal particles, one does not have access to the interior of the particle to apply a potential difference.
EDLs are analogous to the double layer in plasma.
Differential capacitance
EDLs have an additional parameter defining their characterization: differential capacitance. Differential capacitance, denoted as C, is described by the equation below: |
261_18 | where σ is the surface charge and ψ is the electric surface potential. |
261_19 | Electron transfer in electrical double layer |
261_20 | The formation of electrical double layer (EDL) has been traditionally assumed to be entirely dominated by ion adsorption and redistribution. With considering the fact that the contact electrification between solid-solid is dominated by electron transfer, it is suggested by Wang that the EDL is formed by a two-step process. In the first step, when the molecules in the solution first approach a virgin surface that has no pre-existing surface charges, it may be possible that the atoms/molecules in the solution directly interact with the atoms on the solid surface to form strong overlap of electron clouds. Electron transfer occurs first to make the “neutral” atoms on solid surface become charged, i.e., the formation of ions. In the second step, if there are ions existing in the liquid, such as H+ and OH-, the loosely distributed negative ions in the solution would be attracted to migrate toward the surface bonded ions due to electrostatic interactions, forming an EDL. Both electron |
261_21 | transfer and ion transfer co-exist at liquid-solid interface. |
261_22 | See also
Depletion region (structure of semiconductor junction)
DLVO theory
Electroosmotic pump
Interface and colloid science
Nanofluidics
Poisson-Boltzmann equation
Supercapacitor
References
Further reading
External links
The Electrical Double Layer
Chemical mixtures
Colloidal chemistry
Condensed matter physics
Electrochemistry
Matter
Soft matter |
262_0 | The Immigration Depot (, ISO: Āpravāsī Ghāta) is a building complex located in Port Louis on the Indian Ocean island of Mauritius, the first British colony to receive indentured, or contracted, labour workforce from many countries. From 1849 to 1923, half a million Indian indentured labourers passed through the Immigration Depot, to be transported to plantations throughout the British Empire. The large-scale migration of the labourers left an indelible mark on the societies of many former British colonies, with Indians constituting a substantial proportion of their national populations. In Mauritius alone, 68 percent of the current total population is of Indian ancestry. The Immigration Depot has thus become an important reference point in the history and cultural identity of Mauritius. |
262_1 | Unchecked infrastructural development in the mid-20th century means that only the partial remains of three stone buildings from the entire complex have survived. These are now protected as a national monument, under the Mauritian national heritage legislation. The Immigration Depot's role in social history was recognized by UNESCO when it was declared a World Heritage Site in 2006. The site is under the management of the Aapravasi Ghat Trust Fund. Conservation efforts are underway to restore the fragile buildings back to their 1860s state. It is one of two World Heritage Sites in Mauritius, along with Le Morne Brabant.
Etymology
The word ghat is explained by numerous Dravidian etymons such as Kannada gatta (mountain range) Tamil kattu (side of a mountain, dam, ridge, causeway) and Telugu katta and gattu (dam, embankment). |
262_2 | Ghat, a term used in the Indian subcontinent, depending on the context could either refer to a range of stepped-hill such as Eastern Ghats and Western Ghats; or the series of steps leading down to a body of water or wharf, such bathing or cremation place along the banks of a river or pond, Ghats in Varanasi, Dhoby Ghaut or Aapravasi Ghat. Roads passing through ghats are called Ghat Roads.
Name
The name Aapravasi Ghat, which has been in use since 1987, is a direct Hindi translation of "Immigration Depot". Aapravasi is the Hindi word for "immigrant", while ghat literally means "interface"—factually reflecting the structure's position between the land and sea, and symbolically marking a transition between the old life and the new for the arriving indentured immigrants. Alluding to its function as a pit stop to prospective plantation workers, alternatively called coolies, the Immigration Depot has also been known by an older name, the 'Coolie Ghat'. |
262_3 | The prominent use of the Hindi language in Mauritian naming conventions is based on social and ethnic demographics; over half the national population is of Indian ancestry, a direct result of the Indian labour diaspora that passed through the Immigration Depot. In Bihar and Uttar Pradesh, from where majority of these Indian Labourers where brought,"Ghat" is referred to River Bank which is used for Docking of Boats.
Location
The Immigration Depot was built on the east side of the sheltered bay of Trou Fanfaron in Port Louis, the Mauritian capital. The historic complex currently consists of the partial remains of three stone buildings dating back to the 1860s, built on the spot of an earlier depot site. It consists of the entrance gateway and a hospital block, remnants of immigration sheds, and vestiges of the service quarters. |
262_4 | Subsequent land reclamations as a result of urban development have moved the Immigration Depot's location further inland. The Caudan Waterfront, a marina being developed as an economic and tourist centre, is situated beyond the site.
History
Background
The area where the building complex is situated, Trou Fanfaron, was the landing point for the French East India Company, which took possession of Mauritius in 1721. Slaves were imported from Africa, India and Madagascar to construct defensive walls and a hospital during the early phase of settlement. By the mid-18th century, sugar plantations had been developed on the Island of Mauritius, utilizing slave labour. |
262_5 | In 1810, during the Napoleonic Wars, Mauritius passed to British control, as confirmed in the Treaty of Paris, at a time when the British Empire was expanding its influence in the Indian Ocean region. British commercial interest led to the rise in the production of sugar, which became the most valuable commodity in European trade beginning in the mid-18th century throughout the empire in general, leading to the development of infrastructure for Port Louis as a free port in particular. |
262_6 | The abolition of slavery in European colonies in 1834, however, posed a problem for sugar plantations as their operations were highly dependent on slave labour. There was a demand for cheaper intensive labour, as the now emancipated slaves were negotiating for higher wages and better living conditions. As a result, the British government conceived of a plan to replace the emancipated Africans with labourers from other parts of the world. The first wave of new plantation workers were labourers from the Portuguese island of Madeira, freed African-Americans from the U.S. and impoverished Chinese seeking greener pastures. Even though the ethnicity of the plantation workers had changed, the poor working conditions and low living standards remained. These labourers, in the end, could not withstand the manioc root and subsistence cultivation. |
262_7 | At the time, India had been experiencing a depressed economy. This was further aggravated by the Indian Rebellion of 1857 which devastated the northern part of the subcontinent. The hard-working but indigent Indians seemed suited to agricultural labour on the plantations, able to work hard for low wages, providing a potentially massive source of cheap labour. The 'Great Experiment', as the indentured program came to be known, called for these prospective labourers, under a contract labour scheme, to be transported to plantations across the empire to supply the necessary agricultural manpower. This was a system whereby the prospective labourers agreed to work for a determined period of time in return for their cost of passage, basic accommodation and a small wage. |
262_8 | Indentured laborers in Mauritius
Mauritius became the focus of the Great Experiment, as its plantation economy was still in a state of expansion, hence with room for agricultural flexibility, in contrast to those of the West Indies, which were considered exhausted. The long term planning needed in agriculture meant that plantations were generally unable to respond to the sudden market changes. When the sugar beet proved to be a viable and cheaper alternative to the sugar cane, the established sugar plantations throughout the Caribbean became economic liabilities, while thousands of their contracted workers and slaves were left to wallow. In addition, the island's proximity to India was also an advantage. |
262_9 | From 1834 to 1849, when the first migrations of indentured labourers began, no fixed depot had been established to accommodate the immigrants arriving in Port Louis. The thousands of migrants arriving annually put a stress on the lack of a specialized facility. In 1849, a building dating back to the French administration in the Trou Fanfaron area was chosen as the core of a planned structural complex that would become the permanent depot for immigration. The Immigration Depot, as it came to be known, was continuously enlarged in response to the high number of migrants. This lasted until 1857, when all the available land had been occupied. The adequate space allowed the facility to deal with as much as 1,000 prospective laborers at any one time. Further modifications, for the purpose of service convenience, hygiene and transport, were continuously done. However, the competition from beet sugar caught up with Mauritius's sugar cane estates. The spread of a malaria epidemic in the 1860s |
262_10 | further drove shipping away from the colony, leading to a decline of indentured immigration, culminating in 1923, when it had completely ceased. By then, an estimated 450,000 indentured labourers from India had passed through the Immigration Depot throughout its existence. |
262_11 | State of preservation and protection
The end of indentured immigration meant that the Immigration Depot had served its purpose. After 1923, the buildings were put to other uses. The structures remained extant until the 1970s, when the construction of a bus station and a corresponding motorway led to the demolition of some of the buildings. |
262_12 | A renewed interest on the site's importance in the 1980s was sparked by the visit to the site by the late Indian Prime Minister Indira Gandhi in 1970. This led to the protection of the complex's remains as a national monument in 1987, through the national heritage legislation. A landscape project over a part of the site and a series of restoration works were initiated in the 1990s. The lack of a formal conservation plan or a methodical archaeological approach have call into question the site's historic authenticity. 2001 was a landmark year for the site. The Aapravasi Ghat Trust Fund was established to manage the site directly. Its responsibilities include overseeing the excavations and implementing corrective actions on restorations that were haphazardly done since the 1990s. Among the previous preservation works that are being reversed are the landscape project, the hospital building's roof installation, which unfortunately used modern materials, the use of native lime mortar |
262_13 | technique in the reconstruction and maintenance of the remaining stone walls, and devising an archaeological strategy to document finds and discoveries, as well as to safeguard the existing artifacts. The objective of the conservation efforts is for the site to regain its appearance in the 1860s. The site's name was officially changed to Aapravasi Ghat that same year. The name change was not without controversy. Although it was meant to reflect the Hindu Indian majority of indentured labourers, the use of the Hindi translation swept away the myriad of other ethnic and religious populations that also passed through the Immigration Depot. |
262_14 | Facilities
The uncontrolled urban development after the abolition of the indentured system and the late initiative to conserve the site in late 20th century meant that only the partial remains of the place have survived. From the complex founded in 1849, experts estimate that only about 15% still authentically exists today. However, records of the building plan and photographs, as well as recent archaeological evidence, allow for the precise reconstruction of the complex. |
262_15 | Immigrants arriving via the "coolie ships" on the wharf of Trou Fanfaron were led to the Immigration Depot via a series of 14 stone steps, which are presently intact. The walls protecting the wharf along the waterfront are made from a mosaic of dressed stones, as a result of continuous reconstruction over a long period of time. Land reclamations carried out over time to develop the Trou Fanfaron harbor have rendered the historic wharf unusable. The stone steps' direct access to the sea, the first parts of the Immigration Depot seen by arriving migrants, has become part of history. |
262_16 | Beyond the stone steps is the building complex, which was centred on a yard. The buildings had characteristic French clay tile roofing, the better to provide insulation and ventilation, and bitumen flooring. Continuous site improvements to accommodate the high number of migrants were carried out, including the installation of planked walls as room dividers by the late 1850s. By 1865, transportation needs led to the construction of a railway, cutting the Immigration Depot into two. Walls were constructed along the track. |
262_17 | The still standing stone-arched gateway, also constructed in 1865, greeted the migrants when they entered the complex. Adjoining the structure is a hospital building, consisting of seven rooms that accommodated the staff, including a guard's room, kitchen, surgery room and staff privies. Of these, only the gatekeeper's office and surgery room have survived, while archaeological remains of the kitchen and privies have been found. The remnant of the hospital building received a new roof installation in 2000. The use of modern materials however has been questioned by preservation groups. |
262_18 | The migrants also had an immigration shed, where they stayed for up to three days after arrival before being distributed to the respective local sugar estates or being transported to other colonies. The quarter includes a kitchen, while the immigrants' privies are located on a separate service quarter, together with the bathing area. A standing stone wall provides the only mute testimony to the existence of the immigrant shed.
Legacy
Mauritius's sugar industry
Mauritius's local sugar plantations, economically devastated by the emancipation of the slaves, were given a new lifeline with the establishment of the Immigration Depot. The high number of indentured labourers passing through the facility, to be transported to the various territories of the British Empire, proved to be an endless supply stream of cheap labour. In the period of 1834–60, 290,000 Indian labourers arrived. |
262_19 | The pool of labour proved to be so large that, for the next 67 years, indentured contracts were limited to only one year. This sugar revolution led to an increase in volume production, making Mauritius the most important sugar-producing British colony, its sugar export accounting for 7.4 percent of the world's total production by the 1850s. |
262_20 | Mauritius's dependence on its sugar estates to sustain its economy continued into the early 20th century. The economy prospered during World War I, when supply shortages led to the rise in the market price of sugar. The eventual fall in the price of sugar in the 1930s due to the Depression, the mono-crop agricultural industry and the abolition of the indentured labor system have made the Mauritian economy vulnerable, which culminated in labour unrests in 1937. World War II further aggravated the situation. Hence, economic reforms were carried out to diversify agricultural production and develop other industries beginning in 1945. In the mid-1990s, the agricultural sector only accounted for one-eighth of the country's gross national product, although sugar production still generates one-third of Mauritius's export earnings, and occupies about 80 percent of the total arable land.
The global system of indentured laborers |
262_21 | Mauritius was not the pioneering site for the use of indentured labour. In the 17th century, substantial numbers of indentured servants, of European origin, arrived in America, in what were then the Thirteen Colonies. By the 18th century, it has been estimated that over half of the population of white immigrants in the British colonies of North America may have been indentured servants. However, the scale of the system that was put into operation in Mauritius was unprecedented. It immediately spread throughout the colonies of the British Empire, and was imitated by other European powers, while the Indian labor force was also employed beyond the sugarcane fields, in such workplaces as mines and even railways. |
262_22 | The global system of indentured labourers was abolished in 1918, although in Mauritius, the Immigration Depot still continued operating until 1923. By then, the Great Experiment had seen the transportation of an estimated two million people throughout the world, with Mauritius welcoming the largest contingent of indentured labourers, reaching nearly half a million Indian immigrants. In total, 1.2 million Indian migrants were handled by emigration depots worldwide, becoming the global working class of the British Empire. On a larger picture, the migration of indentured labourers is but a small portion of the Indian diaspora, which has continued through the 20th century to contemporary times. It is estimated that up to 20 million Indians have emigrated from their homeland, making it the largest diaspora in modern times. |
262_23 | Thus, the Immigration Depot is considered to be the site where the modern, large-scale indentured labour diaspora began—the system didn't only sustain the plantation economies of the British Empire, but also resulted in the transplantation of cultures and shaping of the national identity of former colonies. Countries from the Caribbean to southern Africa to the Pacific currently have substantial Indian populations.
The Mauritian and French poet Khal Torabully, in exploring the mosaic of cultures brought about by the indentured labourers, coined the term "coolitude," re-defining the migration of laborers not just as part of the historical past, but the entanglement of experiences and mosaic imaginaries: |
262_24 | The indentured system also left a sizeable documentary heritage. A comprehensive record was kept of immigrants, from the contracts signed, their photographs, the transportation cost, the accommodation spending and the final destination of labourers. These registers are currently being managed by the Indian Immigration Archives, which is directly administered by the Mahatma Gandhi Institute, an educational institution established in Mauritius, in cooperation with India.
UNESCO, the international organization responsible for the preservation and protection the world's cultural and natural heritage, has recognized the 1,640 m2 site of the Immigration Depot for its outstanding universal importance. It was proclaimed as a World Heritage Site in 2006, citing the buildings as among the earliest explicit manifestations of what was to become a global economic system and one of the greatest migrations in history.
The Mauritian society |
262_25 | The majority of Indian workers arriving at the Immigration Depot came from the northern part of the subcontinent, corresponding to the present states of Bihar and Uttar Pradesh. The region was then in turmoil following the Indian Rebellion of 1857. Smaller numbers of migrants came from Maharashtra and Tamil Nadu. The Indian migrants that passed through the island have left a distinct mark on the Mauritian society. In 1835, a year after the Great Experiment was implemented, Indians constituted less than four percent of Mauritius's population. However, the steady trickle of labourers changed the demographic face of the colony so that, by 1860, Indians made up more than 66 percent of the population. The colony received such a high proportion of the Indian diaspora that historians have noted the dramatic way the local demography had been altered over such a short period of time, more than in any other sugar-producing British territories. No other indentured migration has so definitely |
262_26 | shaped the future of a nation as the movement of Indian workers to Mauritius, with the result of around half a million Indians settling on the island. Today, up to 1.22 million Mauritians, or 68 percent of the national population, have Indian ancestry, called Indo-Mauritians. This Indian heritage, however, had been extant even before the indentured system began, with merchants from the subcontinent, together with Chinese counterparts, settling on the island. In 1806, when Mauritius was still under the French administration, official statistics showed that there were already 6,162 Indians living on the island, in the eastern suburb of Port Louis, known as Camp des Malabars. |
262_27 | Beginning in the 1840s, the emancipated labourers, or those with concluded contracts, were able to save money and buy their own lands, mostly outside the rural sugar estates, permanently settling in Mauritius. The increasing number of these freed labourers preferring to stay in the colony gave rise to a new class of rural Indian peasantry. Their limited skills meant that they engaged in small-scale crop cultivation to earn a living, while others were able to work as traders or hawkers. The class of rural Indians gained in importance as the sugar industry moved into the 20th century. The struggling sugar barons sold portions of their properties to the Indian merchants in what became known as the Great Morcellement Movement. Thus, the Indians, or Indo-Mauritians, became the first non-whites to own lands in the colony. |
262_28 | By the 1920s, the properties of Indo-Mauritians had already accounted for 40 percent of Mauritius's arable lands. They eventually took control of a substantial part of the agricultural economy, leading to the growth of rural villages and giving rise to a bourgeoisie that would continue to influence to island's post-colonial politics.
Meanwhile, the second-generation Indian immigrants, who were exposed to the cultures of foreign land and were more attuned to British policies, were able to work beyond the agricultural sector. These Western-educated skilled professionals were employed by the British in the Colonial Service. In the British territories bordering the Indian Ocean, they took up a large share of the clerical positions in the bureaucracy. Slowly making their way up, many had achieved respectable positions by the beginning of the 20th century. |
262_29 | Beyond politics, the settlement of Indian migrants on the island resulted in a melting pot of culture, intermixing with African, Chinese, Creole, and European influences. The celebration of Hindu festivals has become part of the Mauritian calendar. A religious Hindu ceremony is held annually on the second day of November, a national holiday to commemorate the arrival of indentured laborers at the Immigration Depot to honor the (Hindi for "ship-mates", or "ship-brother") spirits. The lake of Grand Bassin, also known as Ganga Talao, located in the center of the island has become an object of sacred pilgrimage by the Indo-Mauritians professing their Hindu faith. The Mauritian style of architecture, using lime mortar, consisting of a mixture of yogurt, egg white, butter and sesame oil, as a binding material for stone structures, also has an Indian origin. This same method of construction is being utilized by the Aapravasi Ghat Trust Fund to conserve the remnants of the Immigration Depot |
262_30 | complex. |
262_31 | See also
History of Mauritius
Culture of Mauritius
Non-resident Indian and Person of Indian Origin
Indentured servants
Coolies
References
External links
Aapravasi Ghat World Heritage Site
Coolitude and the symbolism of the Aapravasi ghat
The aapravasi ghat (in French)
En ce cinquième anniversare du Ghat, une belle expérience de l'humanisme du Divers
World Heritage Sites in Mauritius
History of Mauritius
Government buildings in Mauritius
Government buildings completed in 1849
Human migration
Indian diaspora in Mauritius
1849 establishments in the British Empire
Buildings and structures in Port Louis |
263_0 | One of the major depositional strata in the Himalaya is the Lesser Himalayan Strata from the Paleozoic to Mesozoic eras. It had a quite different marine succession during the Paleozoic, as most parts of it are sparsely fossiliferous or even devoid of any well-defined fossils. Moreover, it consists of many varied lithofacies, making correlation work more difficult. This article describes the major formations of the Paleozoic – Mesozoic Lesser Himalayan Strata, including the Tal Formation, Gondwana Strata, Singtali Formation and Subathu Formation. |
263_1 | Geological background
The Himalayan mountain chain is a fold and thrust belt that can be divided into four units bounded by thrusts from south to north: the Sub-Himalaya, Lesser Himalaya, Greater Himalaya and Tethyan Himalaya. The Lesser Himalayan Zone has a lower relief and elevation of the mountains compared to Greater Himalaya. The Lesser Himalaya Sequence (LHS) is bounded by two main thrusts: the Main Central Thrust (MCT) in the north and the Main Boundary Thrust (MBT) in the south. |
263_2 | The main layers of the LHS includes non-fossiliferous, low-grade, metasedimentary rocks, metavolcanic strata and augen gneiss. These have been dated as an age ranging from 1870 Ma to 520 Ma (i.e. Proterozoic to Cambrian). Near the end of the Early Cambrian, there was a regional diastrophism (i.e. deformation of the Earth's crust) or crustal movement that heaved up the Indian subcontinent, interrupting the sedimentation in the Lesser Himalaya and causing a widespread unconformity in Nepal. This is known as the Great Lesser Himalayan Unconformity, which separates the older LHS from the overlying younger LHS that has an age of Permian to Middle Eocene. |
263_3 | During the Paleozoic and Mesozoic, the LHS starts from the basal Tal Formation, which is part of the Outer Lesser Himalayan sequence in the Garhwal Himalaya. The Tal was deposited between the period of the Late Proterozoic to Palaeozoic Cambrian. After that, there was a great hiatus between the Middle Proterozoic rocks and the overlying Palaeocene-Eocene strata. This indicates that the LHS experienced a long period of denudation or non-deposition in the Western Himalaya (e.g. in the Jumla area), resulting in missing Gondwana Strata in Jumla during the Mesozoic (see more in the table of "Gondwana Strata of LHS in Western and Central Nepal"). In the Central and Eastern Himalaya, Gondwana strata from the Permian to Paleocene were preserved unconformably onto the older LHS. The next succession of the LHS in the Garhwal Himalaya comes to the Singtali Formation, which was deposited from the Late Cretaceous to Palaeocene, followed by the Subathu Formation, which was deposited from the Late |
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