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Acid rain
What is acid rain? "Acid rain" is a term used to express several ways that acids fall out of the atmosphere. This rain containing acidic substances that causes damage to plant life, lakes and aquatic life, crops, buildings and human health. A more precise term is acid deposition, which has two parts: wet (refers to acidic rain, fog, and snow) and dry (refers to acidic gases and particles).

Causes Acid rain is caused by emissions of sulphur dioxide and nitrogen oxides. While natural sources of sulphur oxides and nitrogen oxides do exist, most of the sulphur and the nitrogen emissions occurring are of human origin. These pollutants arise from the use of coal in the production of electricity, from base metal smelting, and from fuel combustion in vehicles. Once released into the atmosphere, they could be converted chemically into other pollutants as nitric acid and sulfuric acid, both of which dissolve easily in water. The consequential acidic water can be carried distances by the winds, returning to Earth as acid rain.

Acid Rain measurement Acid rain is measured using a scale called "pH" goes from 0 to 14. The lower a substance's pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is somewhat acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5. The pH scale is logarithmic which means that the difference between each number is not linear. For instance, a pH of 5 is 10 times more acidic than a pH of 6, and a pH of 4 is 100 times more acidic than a pH of 6 and so on.

Normal rain The only place on earth where pure water is found is in a laboratory. Rain water always contains small amounts of impurities. These impurities come from dust particles or are absorbed from the gases in the air. If pure water is exposed to the air it absorbs carbon dioxide to form carbonic acid and becomes acidic, dropping from pH 7 to pH 5,6. Even in remote, unpopulated areas rain can reach a pH of 4, 5. However, a pH of less than 4,5 in rain is almost certainly caused by pollution.

General Effects Sometimes, the environment can naturally adapt to acid rain. However, in most cases it takes many years for ecosystems to recover from acid deposition. As the acidic water flows, it affects many species of plants and animals. These effects depend on many factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that count on the water. Acid rain has destroyed plant and animal life in lakes, damaged forests and crops, endangered marine life in coastal waters, eroded structures, and contaminated drinking water. In addition, acid rain assist damage the building materials and paints. The acid rain can harm public health and expose wildlife at risk directly and as a result of alterations to food sources and habitats.

Effects of acid rain on plant Acid rain horribly influences the green life in the earth. Both natural vegetation and crops are affected by acid rain. The acidic rainfall damages the roots, causing the growth of the plant to be stunted or most likely its death. Nutrients present in the soil, are damaged by the acidity. Useful micro organisms, which release nutrients from decaying organic matter into the soil, are killed off, resulting in lack of nutrients being provided for the plants. The acid rain, falling on the plants damages the waxy layer on the leaves and makes the plant exposed to diseases. The cumulative effect means that if the plant survives it will be weak and unable to stand climatic conditions like strong winds, heavy rainfall, or dry periods.

Effects of acid rain on aquatic life The acid rain causes harmful elements like mercury and aluminium to be leaked from the rocks and it is then carried into the lakes where aquatic life may be affected. As the water gets more acidic its pH goes down. As the pH reaches 5.5, plankton, certain insects and crustaceans begin to die. At a pH of around 5.0, the fish population begins to die. When the pH drops below 5.0, all the fish have died, and the bottom of the lake lies covered with unresolved objects.

Effects on animals and birds Animals and birds, like waterfowl or beavers, which depended on the water for food sources or as a habitat, also begin to die, as the water is getting acidic. Due to the effects of acid rain, animals, which depended on plants for their food, also begin to suffer. Tree dwelling birds and animals begin to suffer due to loss of habitat.

Effects on humans People who depend on fish and other aquatic life suffer as a result from the acidic rain. Eating fish, which may perhaps have been infected by mercury, can cause health problems. In addition to loss of plant and animal life as food sources, acid rain gets into the food we eat, the water we drink, as well as the air we breathe. The acidic water moving through pipes causes harmful aspects like lead and copper to be leached into the water. Aluminium that dissolves more easily in acid rain as compared to pure rainfall has been linked to Alzheimer’s disease. The treatment of urban water supplies may not include removal of elements like Aluminium, and so is a serious problem in cities too. In addition, acid rain and acidifying pollutants can accelerate corrosion of building materials such as stone, brick, concrete and metal.

CORBA
CORBA is the acronym for Common Object Request Broker Architecture is a standard sponsored by the Object Management Group (OMG), a nonprofit consortium of software vendors. CORBA is an architecture that enables pieces of programs, called objects, to communicate with one another regardless of what programming language they were written in or what operating system they are running on.

CORBA is an Application Programming Interface (API) and system definition specification; it is not a piece of code. It provides mechanism by which objects transparently make requests to and receive responses from other objects on different platforms in heterogeneous distributed environments. For example, a C++ object running on one machine can interact with an object on another machine which is implemented in Common Lisp.

The CORBA specification describes a computer architecture that is object-oriented, distributed, language-independent, and hardware-neutral.

The CORBA’s components
Object Request Broker (ORB)The central component of CORBA is the ORB. It encloses the entire communication infrastructure to identify and locate objects, handle connection management and deliver data.

Interface Definition Language (IDL) The OMG-standard language for defining the interfaces for all CORBA objects. An IDL interface declares a set of operations, exceptions, and attributes. IDL does not include implementations for operations it is only a language for defining interfaces. The purpose of IDL is to separate interface from implementation. This separation makes it possible to: •	Improve the modularity and specification of software components. •	Transparently distribute implementation across process and host boundaries. •	Write language-independent applications.

Dynamic Invocation Interface (DII) This interface allows a client to directly access the basic request mechanisms provided by an ORB. DII is used by a client to dynamically build a request to be sent to a server.

Interface Repository (IFR) An online database that contains the definitions of the interfaces that determine the CORBA contracts between client and server applications and also holds type definitions.

Object Adapters The Object Adapter helps the ORB with delivering requests to the object and with activating the object. More significantly, an object adapter associates object implementations with the ORB and can be specialized to provide support for certain object implementation styles.