Karst topography

Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite.
Due to subterranean drainage, there may be very limited surface water, even to the absence of all rivers and lakes. Many karst regions display distinctive surface features, with sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by a superimposed non-soluble rock strata. Some karst regions include thousands of caves, even though evidence of caves that are big enough for human exploration is not a required characteristic of karst.

Background
The geographer Jovan Cvijić (1865–1927) was born in western Serbia and studied widely in the Dinaric Kras region. His publication of Das Karstphänomen (1893) established that rock dissolution was the key process and that it created most types of dolines, "the diagnostic karst landforms". The Dinaric Kras thus became the type area for dissolutional landforms and aquifers; the regional name kras, Germanicised as "karst", is now applied to modern and paleo-dissolutional phenomena worldwide. Cvijić related the complex behaviour of karstic aquifers to development of solutional conduit networks and linked it to a cycle of landform evolution. He is recognized as "the father of karst geomorphology".
Different terms for karst topography exist in other languages—for example, yanrong in Chinese and tsingy in Malagasy. The international community has settled on karst, the German name for Kras, a region in Slovenia partially extending into Italy, where it is called "Carso" and where the first scientific research of a karst topography was made. The name has a pre-Indo-European origin (from karra meaning "stone"), and in antiquity it was called "Carusardius" in Latin. The Slovene form grast is attested since 1177, and the Croatian kras since 1230

Chemistry

Karst landforms are generally the result of mildly acidic water acting on soluble bedrock such as limestone or dolostone. The carbonic acid that causes these features is formed as rain passes through the atmosphere picking up CO2, which dissolves in the water. Once the rain reaches the ground, it may pass through soil that may provide further CO2 to form a weak carbonic acid solution: H2O + CO2 → H2CO3 (the acid). Recent studies of sulfates, in karst waters, suggests sulfuric acid and hydrosulfuric acid may also play an important role in karst formation.
This mildly acidic water begins to dissolve the surface along with any fractures or bedding planes in the limestone bedrock. Over time, these fractures enlarge as the bedrock continues to dissolve. Openings in the rock increase in size, and an underground drainage system begins to develop, allowing more water to pass through the area, and accelerating the formation of underground karst features.
Somewhat less common than this limestone karst is gypsum karst, where the solubility of the mineral gypsum provides many similar structures to the dissolution and redeposition of calcium carbonate.

Formations

The karstification of a landscape may result in a variety of large or small scale features both on the surface and beneath. On exposed surfaces, small features may include flutes, runnels, clints and grikes, collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes (closed basins), vertical shafts, foibe (inverted funnel shaped sinkholes), disappearing streams, and reappearing springs. Large-scale features may include limestone pavements, poljes and blind valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers or haystack/eggbox landscapes. Beneath the surface, complex underground drainage systems (such as karst aquifers) and extensive caves and cavern systems may form.

Erosion along limestone shores, notably in the tropics, produces karst topography that includes a sharp makatea surface above the normal reach of the sea and undercuts that are mostly the result of biological activity or bioerosion at or a little above mean sea level. Some of the most dramatic of these formations can be seen in Thailand's Phangnga Bay and Halong Bay in Vietnam.
Calcium carbonate dissolved into water may precipitate out where the water discharges some of its dissolved carbon dioxide. Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time. In caves, a variety of features collectively called speleothems are formed by deposition of calcium carbonate and other dissolved minerals.
A karst river may disappear underground a number of times and spring up again in different places, usually under a different name (like Ljubljanica, the river of seven names).
An example of this is the Popo Agie River in Fremont County, Wyoming. Simply named "The Sinks" and Sinks Canyon State Park, the river flows into a cave in a formation known as the Madison Limestone, and then rises again a half-mile down the canyon in a placid pool. When the river was dyed, it took two hours for the dye to reach the rising a short distance away.

Hydrology

Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains.
A karst fenster is where an underground stream emerges onto the surface between layers of rock, cascades some feet, and then disappears back down, often into a sinkhole.
Water supplies from wells in karst topography may be unsafe, as the water may have run unimpeded from a sinkhole in a cattle pasture, through a cave and to the well, bypassing the normal filtering that occurs in a porous aquifer. Karst formations are cavernous and therefore have high rates of permeability, resulting in reduced opportunity for contaminants to be filtered out.
Groundwater in karst areas is just as easily polluted as surface streams. Sinkholes have often been used as farmstead or community trash dumps. Overloaded or malfunctioning septic tanks in karst landscapes may dump raw sewage directly into underground channels.
The karst topography itself also poses difficulties for human inhabitants. Sinkholes can develop gradually as surface openings enlarge, but quite often progressive erosion is unseen and the roof of an underground cavern suddenly collapses. Such events have swallowed homes, cattle, cars, and farm machinery.
The Driftless Area National Wildlife Refuge in Iowa protects Discus macclintocki, a species of ice age snail surviving in air chilled by flowing over buried karst ice formations.

Lithography

Lithography (from Greek λίθος - lithos, 'stone' + γράφω - graphο, 'to write') is a method for printing using a stone (lithographic limestone) or a metal plate with a completely smooth surface. Lithography uses oil or fat and gum arabic to divide the smooth surface into hydrophilic regions which accept the ink, and hydrophobic regions which reject it and thus become the background. By contrast, in intaglio printing a plate is engraved, etched or stippled to make cavities to contain the printing ink, and in woodblock printing and letterpress ink is applied to the raised surfaces of letters or images.
Invented by Bavarian author Alois Senefelder in 1796, lithography can be used to print text or artwork onto paper or another suitable material. Most books, indeed all types of high-volume text, are now printed using offset lithography, the most common form of printing production. The word "lithography" also refers to photolithography, a microfabrication technique used to make integrated circuits and microelectromechanical systems, although those techniques have more in common with etching than with lithography.

The principle of lithography

Lithography uses simple chemical processes to create an image. For instance, the positive part of an image would be a hydrophobic, or "water hating" chemical, while the negative image would be hydrophilic or "water loving". Thus, when the plate is introduced to a compatible printing ink and water mixture, the ink will adhere to the positive image and the water will clean the negative image. This allows a flat print plate to be used, enabling much longer and more detailed print runs than the older physical methods of printing (e.g., intaglio printing, Letterpress printing).

In the early days of lithography, a smooth piece of limestone was used (hence the name "lithography"—"lithos" (λιθος) is the ancient Greek word for stone). After the oil-based image was put on the surface, a solution of gum arabic in water was applied, the gum sticking only to the non-oily surface. During printing, water adhered to the gum arabic surfaces and avoided the oily parts, while the oily ink used for printing did the opposite.

Lithography on limestone

Lithography works because of the mutual repulsion of oil and water. The image is drawn on the surface of the print plate with a fat or oil-based medium (hydrophobic), which may be pigmented to make the drawing visible. A wide range of oil-based media is available, but the durability of the image on the stone depends on the lipid content of the material being used, and its ability to withstand water and acid. Following the drawing of the image, an aqueous solution of gum arabic, weakly acidified with nitric acid HNO3 is applied to the stone. The function of this solution is to create a hydrophilic layer of calcium nitrate salt, Ca(NO3)2, and gum arabic on all non-image surfaces. The gum solution penetrates into the pores of the stone, completely surrounding the original image with a hydrophilic layer that will not accept the printing ink. Using lithographic turpentine, the printer then removes any excess of the greasy drawing material, but a hydrophobic molecular film of it remains tightly bonded to the surface of the stone, rejecting the gum arabic and water, but ready to accept the oily ink.
When printing, the stone is kept wet with water. Naturally the water is attracted to the layer of gum and salt created by the acid wash. Printing ink based on drying oils such as linseed oil and varnish loaded with pigment is then rolled over the surface. The water repels the greasy ink but the hydrophobic areas left by the original drawing material accept it. When the hydrophobic image is loaded with ink, the stone and paper are run through a press which applies even pressure over the surface, transferring the ink to the paper and off the stone.

Senefelder had experimented in the early 1800s with multicolor lithography; in his 1819 book, he predicted that the process would eventually be perfected and used to reproduce paintings. Multi-color printing was introduced through a new process developed by Godefroy Engelmann (France) in 1837 known as Chromolithography. A separate stone was used for each colour, and a print went through the press separately for each stone. The main challenge was of course to keep the images aligned (in register). This method lent itself to images consisting of large areas of flat color, and led to the characteristic poster designs of this period.

The modern lithographic process

The earliest regular use of lithography for text was in countries using Arabic, Turkish and similar scripts, where books, especially the Qu'ran, were sometimes printed by lithography in the nineteenth century, as the links between the characters require compromises when movable type is used which were considered inappropriate for sacred texts.
High-volume lithography is used today to produce posters, maps, books, newspapers, and packaging — just about any smooth, mass-produced item with print and graphics on it. Most books, indeed all types of high-volume text, are now printed using offset lithography.
In offset lithography, which depends on photographic processes, flexible aluminum, polyester, mylar or paper printing plates are used in place of stone tablets. Modern printing plates have a brushed or roughened texture and are covered with a photosensitive emulsion. A photographic negative of the desired image is placed in contact with the emulsion and the plate is exposed to ultraviolet light. After development, the emulsion shows a reverse of the negative image, which is thus a duplicate of the original (positive) image. The image on the plate emulsion can also be created through direct laser imaging in a CTP (Computer-To-Plate) device called a platesetter. The positive image is the emulsion that remains after imaging. For many years, chemicals have been used to remove the non-image emulsion, but now plates are available that do not require chemical processing.

The plate is affixed to a cylinder on a printing press. Dampening rollers apply water, which covers the blank portions of the plate but is repelled by the emulsion of the image area. Ink, which is hydrophobic, is then applied by the inking rollers, which is repelled by the water and only adheres to the emulsion of the image area--such as the type and photographs on a newspaper page.
If this image were directly transferred to paper, it would create a mirror image and the paper would become too wet. Instead, the plate rolls against a cylinder covered with a rubber blanket, which squeezes away the water, picks up the ink and transfers it to the paper with uniform pressure. The paper rolls across the blanket drum and the image is transferred to the paper. Because the image is first transferred, or offset to the rubber drum, this reproduction method is known as offset lithography or offset printing. http://www.compassrose.com/static/Offset.jpg
Many innovations and technical refinements have been made in printing processes and presses over the years, including the development of presses with multiple units (each containing one printing plate) that can print multi-color images in one pass on both sides of the sheet, and presses that accommodate continuous rolls (webs) of paper, known as web presses. Another innovation was the continuous dampening system first introduced by Dahlgren instead of the old method which is still used today on older presses (conventional dampening), which are rollers covered in molleton (cloth) which absorbs the water. This increased control over the water flow to the plate and allowed for better ink and water balance. Current dampening systems include a "delta effect or vario " which slows the roller in contact with the plate, thus creating a sweeping movement over the ink image to clean impurities known as "hickies".
The advent of desktop publishing made it possible for type and images to be manipulated easily on personal computers for eventual printing on desktop or commercial presses. The development of digital imagesetters enabled print shops to produce negatives for platemaking directly from digital input, skipping the intermediate step of photographing an actual page layout. The development of the digital platesetter in the late twentieth century eliminated film negatives altogether by exposing printing plates directly from digital input, a process known as computer to plate printing.

Virtual world

A virtual world is a computer-based simulated environment intended for its users to inhabit and interact via avatars. These avatars are usually depicted as textual, two-dimensional, or three-dimensional graphical representations, although other forms are possible (auditory and touch sensations for example). Some, but not all, virtual worlds allow for multiple users.
The computer accesses a computer-simulated world and presents perceptual stimuli to the user, who in turn can manipulate elements of the modeled world and thus experiences telepresence to a certain degree. Such modeled worlds may appear similar to the real world or instead depict fantasy worlds. The model world may simulate rules based on the real world or some hybrid fantasy world. Example rules are gravity, topography, locomotion, real-time actions, and communication. Communication between users has ranged from text, graphical icons, visual gesture, sound, and rarely, forms using touch, voice command, and balance senses.
Massively multiplayer online games commonly depict a world very similar to the real world, with real world rules and real-time actions, and communication. Players create a character to travel between buildings, towns, and even worlds to carry out business or leisure activities. Communication is usually textual, with real-time voice communication using VOIP also possible.
Virtual worlds are not limited to games but, depending on the degree of immediacy presented, can encompass computer conferencing and text based chatrooms. Sometimes, emoticons or 'smilies' are available, to show feeling or facial expression. Emoticons often have a keyboard shortcut. Edward Castronova is an economist who has argued that "synthetic worlds" is a better term for these cyberspaces, but this term has not been widely adopted.

Virtual world concepts

One perception of virtual worlds requires an online persistent world, active and available 24 hours a day and seven days a week, to qualify as a true virtual world. Although this is possible with smaller virtual worlds, especially those that are not actually online, no massively multiplayer game runs all day, every day. All the online games include downtime for maintenance that is not included as time passing in the virtual world. While the interaction with other participants is done in real-time, time consistency is not always maintained in online virtual worlds. For example, EverQuest time passes faster than real-time despite using the same calendar and time units to present game time.
As virtual world is a fairly vague and inclusive term, the above can generally be divided along a spectrum ranging from:
a) massively multiplayer online role-playing games or MMORPGs where the user playing a specific character is a main feature of the game (World Of Warcraft for example).
b) massively multiplayer online real-life/rogue-like games or MMORLGs, the user can edit and alter their avatar at will, allowing them to play a more dynamic role, or multiple roles.
Some would argue that the MMO versions of RTS and FPS games are also virtual worlds if the world editors allow for open editing of the terrains if the "source file" for the terrain is shared. Emerging concepts include basing the terrain of such games on real satellite photos, such as those available through the Google Maps API or through a simple virtual geocaching of "easter eggs" on WikiMapia or similar mashups, where permitted.

Economy

A virtual economy is the emergent property of the interaction between participants in a virtual world. While the designers have a great deal of control over the economy by the encoded mechanics of trade, it is nonetheless the actions of players that define the economic conditions of a virtual world. The economy arises as a result of the choices that players make under the scarcity of real and virtual resources such as time or currency. Participants have a limited time in the virtual world, as in the real world, which they must divide between task such as collecting resources, practicing trade skills, or engaging in less productive fun play. The choices they make in their interaction with the virtual world, along with the mechanics of trade and wealth acquisition, dictate the relative values of items in the economy. The economy in virtual worlds is typically driven by in-game needs such as equipment, food, or trade goods. Virtual economies like that of Second Life, however, are almost entirely player-produced with very little link to in-game needs.
The value of objects in a virtual economy is usually linked to their usefulness and the difficulty of obtaining them. The investment of real world resources (time, membership fees, etc) in acquisition of wealth in a virtual economy may contribute to the real world value of virtual objects. This real world value is made obvious by the trade of virtual items on online market sites like eBay. Recent legal disputes also acknowledge the value of virtual property, even overriding the mandatory EULA which many software companies use to establish that virtual property has no value and/or that users of the virtual world have no legal claim to property therein.
Some industry analysts have moreover observed that there is a secondary industry growing behind the virtual worlds, made up by social networks, websites and other projects completely devoted to virtual worlds communities and gamers. Special websites as GamerDNA, Koinup and others which serve as social networks for virtual worlds users are facing some crucial issue as the DataPortability of avatars across many virtual worlds and MMORPGs.

Furthermore, economical actors are interested by virtual world like 3D video games, instant messaging, search engines and blogs because these are places where they can display targeted advertising, adapted to the people who will see it. Projects about coming video games planned to include advertisements inside the 3D environment.

Virtual worlds and real life

Some virtual worlds have off-line, real world components and applications. Handipoints, for example, is a children's virtual world that tracks chores via customizable chore charts and lets children get involved in their household duties offline. They complete chores and use the website and virtual world to keep track of their progress and daily tasks.

Application domains

Social

Even though Virtual Worlds are often seen as 3D Games, there are many different kinds: forums, blogs, wikis and chatrooms where communities are born. Places which have their own world, their own rules, topics, jokes, members, etc... Each person who belongs to these kinds of communities can find like-minded people to talk to, whether this be a passion, the wish to share information about or just to meet new people and experience new things. Some users develop a double personality depending on which world they are interacting with. Depending on whether that person is in the real or virtual world can impact on the way they think and act. It is not all about video games and communities, virtual world also plays a part in the social as it can allow people to speak or share knowledge with each other. Best examples are instant messaging and visio-conferences which allow people to create their own virtual world.
Systems that have been designed for a social application include:
a) Active Worlds

b) Second Life
c) Smallworlds

Medical

Virtual worlds can also be used, for instance by the Starlight Children's Foundation, to help hospitalised children (suffering from painful diseases or autism for example) to create a comfortable and safe environment which can expand their situation, experience interactions (when you factor in the involvement of a multiple cultures and players from around the world) they may not have been able to experience without a virtual world, healthy or sick. Virtual worlds also enable them to experience and act beyond the restrictions of their illness and help to relieve stress. Disabled or chronically invalided people of any age can also benefit enormously from experiencing the mental and emotional freedom gained by temporarily leaving their disabilities behind and doing, through the medium of their avatars, things as simple and potentially accessible to able, healthy people as walking, running, dancing, sailing, fishing, swimming, surfing, flying, skiing, gardening, exploring and other physical activities which their illnesses or disabilities prevent them from doing in real life. They may also be able to socialise, form friendships and relationships much more easily and avoid the stigma and other obstacles which would normally be attached to their disabilities. This can be much more constructive, emotionally satisfying and mentally fulfilling than passive pastimes such as television watching, playing computer games, reading or more conventional types of internet use.
Psychologically virtual worlds can help players become more familiar and comfortable with actions they may in real-life feel reluctant or embarrassed. For example, in World of Warcraft, /dance is the emote for a dance move which a player in the virtual world can "emote" quite simply. And a familiarization with said or similar "emotes" or social skills (such as, encouragement, gratitude, problem-solving, and even kissing) in the virtual world via avatar can make the assimilation to similar forms of expression, socialization, interaction in real life smooth. Interaction with humans through avatars in the virtual world has potential to seriously expand the mechanics of one's interaction with real-life interactions.

Cyborg

A cyborg is a cybernetic organism (i.e., an organism that has both artificial and natural systems). The term was coined in 1960 when Manfred Clynes and Nathan Kline used it in an article about the advantages of self-regulating human-machine systems in outer space. D. S. Halacy's Cyborg: Evolution of the Superman in 1965 featured an introduction which spoke of a "new frontier" that was "not merely space, but more profoundly the relationship between 'inner space' to 'outer space' -a bridge...between mind and matter." The cyborg is often seen today merely as an organism that has enhanced abilities due to technology, but this perhaps oversimplifies the category of feedback.
Fictional cyborgs are portrayed as a synthesis of organic and synthetic parts, and frequently pose the question of difference between human and machine as one concerned with morality, free will, and empathy. Fictional cyborgs may be represented as visibly mechanical (e.g. the Cybermen in the Doctor Who franchise or The Borg from Star Trek); or as almost indistinguishable from humans (e.g. the "Human" Cylons from the re-imagining of Battlestar Galactica). The 1970s television series the Six Million Dollar Man featured one of the most famous fictional cyborgs. Cyborgs in fiction often play up a human contempt for over-dependence on technology, particularly when used for war, and when used in ways that seem to threaten free will. Cyborgs are also often portrayed with physical or mental abilities far exceeding a human counterpart (military forms may have inbuilt weapons, among other things).
Real (as opposed to fictional) cyborgs are more frequently people who use cybernetic technology to repair or overcome the physical and mental constraints of their bodies. While cyborgs are commonly thought of as mammals, they can be any kind of organism.

Individual cyborgs
Generally, the term "cyborg" is used to refer to a man or woman with bionic, or robotic, implants.
In current prosthetic applications, the C-Leg system developed by Otto Bock HealthCare is used to replace a human leg that has been amputated because of injury or illness. The use of sensors in the artificial C-Leg aids in walking significantly by attempting to replicate the user's natural gait, as it would be prior to amputation. Prostheses like the C-Leg and the more advanced iLimb are considered by some to be the first real steps towards the next generation of real-world cyborg applications. Additionally cochlear implants and magnetic implants which provide people with a sense that they would not otherwise have had can additionally be thought of as creating cyborgs.
In 2002, under the heading Project Cyborg, a British scientist, Kevin Warwick, had an array of 100 electrodes fired in to his nervous system in order to link his nervous system into the internet. With this in place he successfully carried out a series of experiments including extending his nervous system over the internet to control a robotic hand, a loudspeaker and amplifier. This is a form of extended sensory input and the first direct electronic communication between the nervous systems of two humans.

Cyborg proliferation in society

In medicine

In medicine, there are two important and different types of cyborgs: these are the restorative and the enhanced. Restorative technologies “restore lost function, organs, and limbs”. The key aspect of restorative cyborgization is the repair of broken or missing processes to revert to a healthy or average level of function. There is no enhancement to the original faculties and processes that were lost.
On the contrary, the enhanced cyborg “follows a principle, and it is the principle of optimal performance: maximising output (the information or modifications obtained) and minimising input (the energy expended in the process) ”. Thus, the enhanced cyborg intends to exceed normal processes or even gain new functions that were not originally present.
Although prostheses in general supplement lost or damaged body parts with the integration of a mechanical artifice, bionic implants in medicine allow model organs or body parts to mimic the original function more closely. Michael Chorost wrote a memoir of his experience with cochlear implants, or bionic ear, titled "Rebuilt: How Becoming Part Computer Made Me More Human." Jesse Sullivan became one of the first people to operate a fully robotic limb through a nerve-muscle graft, enabling him a complex range of motions beyond that of previous prosthetics. By 2004, a fully functioning artificial heart was developed. The continued technological development of bionic and nanotechnologies begins to raise the question of enhancement, and of the future possibilities for cyborgs which surpass the original functionality of the biological model. The ethics and desirability of "enhancement prosthetics" have been debated; their proponents include the transhumanist movement, with its belief that new technologies can assist the human race in developing beyond its present, normative limitations such as aging and disease, as well as other, more general incapacities, such as limitations on speed, strength, endurance, and intelligence. Opponents of the concept describe what they believe to be biases which propel the development and acceptance of such technologies; namely, a bias towards functionality and efficiency that may compel assent to a view of human people which de-emphasises as defining characteristics actual manifestations of humanity and personhood, in favour of definition in terms of upgrades, versions, and utility.
One of the more common and accepted forms of temporary modification occurs as a result of prenatal diagnosis technologies. Some modern parents willingly use testing methods such as ultrasounds and amniocentesis to determine the sex or health of the fetus. The discovery of birth defects or other congenital problems by these procedures may lead to neonatal treatment in the form of open fetal surgery or the less invasive fetal intervention.
A brain-computer interface, or BCI, provides a direct path of communication from the brain to an external device, effectively creating a cyborg. Research of Invasive BCIs, which utilize electrodes implanted directly into the grey matter of the brain, has focused on restoring damaged eye sight in the blind and providing functionality to paralysed people, most notably those with severe cases, such as Locked-In syndrome.
Retinal implants are another form of cyborgization in medicine. The theory behind retinal stimulation to restore vision to people suffering from retinitis pigmentosa and vision loss due to aging (conditions in which people have an abnormally low amount of ganglion cells) is that the retinal implant and electrical stimulation would act as a substitute for the missing ganglion cells (cells which connect the eye to the brain).
While work to perfect this technology is still being done, there have already been major advances in the use of electronic stimulation of the retina to allow the eye to sense patterns of light. A specialized camera is worn by the subject (possibly on the side of a their glasses frames) the camera converts the image into a pattern of electrical stimulation. A chip located in the users eye would then electrically stimulate the retina with this pattern and the image appears to the user. Current prototypes have the camera being powered by a hand sized power supply that could be placed in a pocket or on the waist.
Currently the technology has only been tested on human subject for brief amounts of time and the amount of light picked up by the subject has been minimal. However, if technological advances proceed as planned this technology may be used by thousands of blind people and restore vision to most of them. Robot assisted surgery is another way cyborgs are being integrated into medicine

In the military

Military organizations' research has recently focused on the utilization of cyborg animals for inter-species relationships for the purposes of a supposed a tactical advantage. DARPA has announced its interest in developing "cyborg insects" to transmit data from sensors implanted into the insect during the pupal stage. The insect's motion would be controlled from a MEMS, or Micro-Electro-Mechanical System, and would conceivably surveil an environment and detect explosives or gas. Similarly, DARPA is developing a neural implant to remotely control the movement of sharks. The shark's unique senses would be exploited to provide data feedback in relation to enemy ship movement and underwater explosives.

Cloud

A cloud is a visible mass of droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or cloud physics branch of meteorology.
On Earth the condensing substance is typically water vapor, which forms small droplets or ice crystals, typically 0.01 mm in diameter. When surrounded by billions of other droplets or crystals they become visible as clouds. Dense deep clouds exhibit a high reflectance (70% to 95%) throughout the visible range of wavelengths. They thus appear white, at least from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases, hence the gray or even sometimes dark appearance at the cloud base. Thin clouds may appear to have acquired the color of their environment or background and clouds illuminated by non-white light, such as during sunrise or sunset, may appear colored accordingly. Clouds look darker in the near-infrared because water absorbs solar radiation at those wavelengths.

Condensation

As air parcels cool due to expansion of the rising air mass, water vapor begins to condense on condensation nuclei such as dust, ice and salt. This process forms clouds. Sometimes an elevated portion of a frontal zone forces broad areas of lift, which form cloud decks such as altostratus or cirrostratus. Stratus is a large dark low cloud deck that tends to form when a stable cool air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions. Clouds can also be formed due to lifting over mountains and other topography

Cirrostratus cloud

Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals, capable of forming halos. They are usually located above 5.5 km . When thick enough to be seen, they are whitish, usually with no distinguishing features. When covering the whole sky and sometimes so thin as to be hardly discernible, this may indicate a large amount of moisture in the upper atmosphere. Cirrostratus clouds sometimes signal the beginning of a warm front and thus may be signs that precipitation might follow in the next 12 to 24 hours.

Circumhorizontal arc

A circumhorizontal arc is an optical phenomenon, an ice-halo formed by plate shaped ice crystals in high level cirrus clouds.
The current accepted technical names are circumhorizon arc or Lower symmetric 46° plate arc. The term 'fire rainbow' coined recently by a journalist is not recognised. It is misleading as the arc is not a rainbow and is not related to fires.
The complete halo is a huge and beautiful multi-coloured band running parallel to the horizon with its center beneath the sun. The distance below the sun is twice as far as the common 22-degree halo. Red is the uppermost colour. Often, when the halo forming cloud is small or patchy, only fragments of the arc are seen.
There is a myth that the halo is rare. How often it is seen depends on location and in particular latitude. In the United States it is a relatively common halo seen several times each summer in any one place. In contrast, it is rare in mid-latitude and northern Europe.
For the halo to form the sun must be very high in the sky, at an elevation of 58° or more. Cirrus cloud or haze containing relatively large plate-shaped ice crystals must also be present. The sun altitude requirement has the consequence that the halo is impossible to see at locations north of 55°N or south of 55°S (although a lunar circumhorizon arc might be visible). In other latitudes it is visible for a greater or lesser time around the summer solstice. Slots of visibility for different latitudes and locations can be looked up on graph. For example, in London, England the sun is only high enough for 140 hours between mid May and late July. Contrast that with Los Angeles with the sun higher than 58 degrees for 670 hours between late March and late September. When the cloudiness of Europe is also taken into account, the halo becomes more than 10-20X more likely to be seen in the United States.
The halo is formed by sunlight entering horizontally-oriented flat hexagon ice crystals through a vertical side face and leaving through the near horizontal bottom face. There is no requirement that the plates be thick. In principle, Parry oriented column crystals can also produce the arc although this is rare.
The 90° inclination between the ray entrance and exit faces produces the well-separated spectral colours and, if the crystal alignment is just right, makes the entire cirrus cloud appear to shine.
A circumhorizontal arc can be difficult to distiguish from an infralateral arc when the sun is high in the sky. The former is always parallel to the horizon whereas the latter curves upwards at its ends.

Cloud iridescence

Cloud iridescence or irisation is the occurrence of colors in a cloud not dissimilar to those seen in oil films on puddles. It is fairly common. The colors are usually pastel and need searching for but sometimes they can be very vivid. Iridescence is most frequent near to the sun and the glare masks it. It is most easily seen by hiding the sun behind a tree or building. Other aids are dark glasses or observing the sky by its reflection in a convex mirror or in a pool of water.
Iridescent clouds are a diffraction phenomenon. Small water droplets or even small ice crystals in clouds individually scatter light. Large ice crystals produce halos - the latter are refraction phenomena not iridescence. Iridescence should similarly be distinguished from the refraction in larger raindrops that gives a rainbow.
If parts of the clouds have droplets (or crystals) of similar size the cumulative effect is seen as colors. The cloud must be optically thin so that most rays encounter only a single droplet. Iridescence is therefore mostly seen at cloud edges or in semi transparent clouds. Newly forming clouds produce the brightest and most colorful iridescence because their droplets are of the same size. When a thin cloud has droplets of similar size over a large extent the iridescence takes on a structured form to give a corona - a central bright disk around the sun or moon surrounded by one or more colored rings.

Al-Kindi

Abū Yūsuf Yaʻqūb ibn Isḥāq al-Kindī (Arabic: أبو يوسف يعقوب إبن إسحاق الكندي‎) (c. 801–873 CE), also known to the West by the Latinized version of his name Alkindus, was an Arab Iraqi polymath: an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist. Al-Kindi was the first of the Muslim Peripatetic philosophers, and is known for his efforts to introduce Greek and Hellenistic philosophy to the Arab world, and as a pioneer in chemistry, cryptography, medicine, music theory, physics, psychology, and the philosophy of science.
Al-Kindi was a descendant of the Kinda tribe which is a well known Arabic tribe native of Najd (present day Saudi Arabia). He was born and educated in Kufa, before pursuing further studies in Baghdad. Al-Kindi became a prominent figure in the House of Wisdom, and a number of Abbasid Caliphs appointed him to oversee the translation of Greek scientific and philosophical texts into the Arabic language. This contact with "the philosophy of the ancients" (as Greek and Hellenistic philosophy was often referred to by Muslim scholars) had a profound effect on his intellectual development, and led him to write original treatises on subjects ranging from Islamic ethics and metaphysics to Islamic mathematics and pharmacology.

In mathematics, al-Kindi played an important role in introducing Indian numerals to the Islamic and Christian world. He was a pioneer in cryptanalysis and cryptology, and devised new methods of breaking ciphers, including the frequency analysis method. Using his mathematical and medical expertise, he developed a scale to allow doctors to quantify the potency of their medication. He also experimented with music therapy.
The central theme underpinning al-Kindi's philosophical writings is the compatibility between philosophy and other orthodox Islamic sciences, particularly theology.

Accomplishments

Al-Kindi was a master of many different areas of thought. Although he would eventually be eclipsed by names such as al-Farabi and Avicenna, he was held to be one of the greatest Islamic philosophers of his time. The historian Ibn al-Nadim (d. 955), described him as:
The best man of his time, unique in his knowledge of all the ancient sciences. He is called the Philosopher of the Arabs. His books deal with different sciences, such as logic, philosophy, geometry, arithmetic, astronomy etc. We have connected him with the natural philosophers because of his prominence in Science.
The Italian Renaissance scholar Gerolamo Cardano (1501–1575) considered him one of the twelve greatest minds of the Middle Ages. According to Ibn al-Nadim, al-Kindi wrote at least two hundred and sixty books, contributing heavily to geometry (thirty-two books), medicine and philosophy (twenty-two books each), logic (nine books), and physics (twelve books). His influence in the fields of physics, mathematics, medicine, philosophy and music were far-reaching and lasted for several centuries. Although most of his books have been lost over the centuries, a few have survived in the form of Latin translations by Gerard of Cremona, and others have been rediscovered in Arabic manuscripts; most importantly, twenty-four of his lost works were located in the mid-twentieth century in a Turkish library. The Theology of Aristotle, a paraphrase of parts of Plotinus' Six Enneads along with Porphyry's commentary, seems to have been edited by Al-Kindi.

Psychology

As an Islamic psychologist, al-Kindi was a pioneer in experimental psychology. He was the first to use the method of experiment in psychology, which led to his discovery that sensation is proportionate to the stimulus. He was also the earliest to realize the therapeutic value of music and attempted to cure a quadriplegic boy using music therapy.
He also dealt with psychology in several other treatises: On Sleep and Dreams (a treatise on dream interpretation), First Philosophy, and Eradication of Sorrow. In the latter, he described sorrow as "a spiritual (Nafsani) grief caused by loss of loved ones or personal belongings, or by failure in obtaining what one lusts after" and then added: "If causes of pain are discernible, the cures can be found." He recommended that "if we do not tolerate losing or dislike being deprived of what is dear to us, then we should seek after riches in the world of the intellect. In it we should treasure our precious and cherished gains where they can never be dispossessed...for that which is owned by our senses could easily be taken away from us." He also stated that "sorrow is not within us we bring it upon ourselves." He developed cognitive methods to combat depression and discussed the intellectual operations of human beings .

Cryptography and mathematics

Al-Kindi was a pioneer in cryptography, especially cryptanalysis. He gave the first known recorded explanation of cryptanalysis in A Manuscript on Deciphering Cryptographic Messages. In particular, he is credited with developing the frequency analysis method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break ciphers (i.e. cryptanalysis by frequency analysis). This was detailed in a text recently rediscovered in the Ottoman archives in Istanbul, A Manuscript on Deciphering Cryptographic Messages, which also covers methods of cryptanalysis, encipherments, cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic. Al-Kindi also had knowledge of polyalphabetic ciphers centuries before Leon Battista Alberti. Al-Kindi's book also introduced the classification of ciphers, developed Arabic phonetics and syntax, and described the use of several statistical techniques for cryptoanalysis. This book apparently antedates other cryptology references by several centuries, and it also predates writings on probability and statistics by Pascal and Fermat by nearly eight centuries.
Al-Kindi authored works on a number of other important mathematical subjects, including arithmetic, geometry, the Indian numbers, the harmony of numbers, lines and multiplication with numbers, relative quantities, measuring proportion and time, and numerical procedures and cancellation. He also wrote four volumes, On the Use of the Indian Numerals (Ketab fi Isti'mal al-'Adad al-Hindi) which contributed greatly to diffusion of the Indian system of numeration in the Middle East and the West. In geometry, among other works, he wrote on the theory of parallels. Also related to geometry were two works on optics. One of the ways in which he made use of mathematics as a philosopher was to attempt to disprove the eternity of the world by demonstrating that actual infinity is a mathematical and logical absurdity.