Category Archives: Science & Technology


Types of Buses

Since the appearance of motor vehicles, public transportation has been enhanced by greatly. Presently, different means of public transportation has been known such as subways, trolley cars, buses, planes and taxi cabs. Among these different forms of transportation, buses are perhaps the most popular form of public transportation all over the world. Buses can be used in several different ways. There are school buses, public buses, coach buses and even tour buses and all are meant to perform different functions. School buses are the most commonly used vehicles on the roads which are meant to pick and drop the school children from home to school and school to home. Let us have a look at some of the different types of buses and their functions.

Tour Buses: As the name suggests, these buses are meant for tourism where tourists are taken to different places on these buses like New York, Philadelphia, Los Angeles, and so on. For instance, if we talk about Philadelphia, these buses take the tourists to the Constitution Center, the Art Museum, Independence Mall, Betsy Ross’ House and Old City. Tour buses are also common in London. Double decker buses are commonly associated with London and make their way into the United States later at some time. These double deckers are widely used in the cities mentioned earlier.

Coach Buses: Coach Buses are the buses which are there to arrange long term trips across the country. Even these buses are used to take athletic teams from one place to another, from airports to hotels etc. A standard coach bus normally has a bathroom, comfortable seating and even a TV as well. These buses are normally adorned with decals and paint to achieve harmony between the team’s colors and logos.

Public Transit: These are likely to be the most frequent buses which one can see on the roads. Public transit buses are the buses for public which run on different routes within the city to take the people from one place to another, especially from home to offices or schools and vice versa. Other than that these buses normally cover all the major places in the city such as cinemas, shopping malls, sport auditoriums, museums, tourist resorts etc. Public transit buses are usually controlled by the city government such as in Philadelphia, the buses are run by the Southeastern Pennsylvania Transportation Authority (SEPTA).

Tramcars: These are the types of buses which are widely used today. Trams or tramcars are the buses which provide transportation on a short route such as to transport people back and forth in parking lots, airport, or theme parks. However, they can perform the role of public transit buses as well in some countries, though smaller in size than a normal bus, but perform the same function.

These are some of the different types of buses which are used in different parts of the world. The term bus is in fact taken from the word ‘omnibus’ which means ‘for all’. This implies that that bus is something that can be used by everyone. People belongs to different phases of life, ages can make use of this public transportation. It is worth mentioning here that the first bus was used by the French in 1862, but then horses were used to pull those buses.


Types of Metal

The term metal is always hard to define. However, a dictionary definition of metal is, “a substance that is usually hard and shiny and that heat and electricity can travel through.” Metals are found with changing degrees of hardness, malleability, ductility, hardness and density. Malleability is a property of being easily molded into different shapes without breaking or cracking while ductility is property given to the metals that can be made into thin wire. Almost all the metals have a certain melting point and can be combined with other metals by melting to form alloys. It is important to note here that all the metals except mercury are solid at normal temperatures. Following are given some of the different types of metal.


Aluminum is lightweight metal that is commonly used all over the world. In its raw form, it is extremely strong and to make it suitable for use is often alloyed with silicon. Generally 1 percent of silicon of silicon is used with aluminum. However, in case of casting alloys, 12 percent of silicon is used.

Raw aluminum also has a bad tolerance to corrosion, however, the self generating oxide layer enable it to be used in environments more prone to corrosion.

Raw aluminum has poor corrosive resistance, but thanks to a protective self generating oxide layer, the material can be used in corrosive environments. Anodizing process is used to check the quality of oxide layer.

Foamed Aluminum

Where light aluminum structures are required, foamed aluminum is used. The aluminum is foamed by mixing the aluminum with the titanium hydride prior to casting as a result of which hydrogen gas foams the aluminum. Foamed aluminum has a porous surface and an additional layer of solid aluminum is used to cover this. Contrary to honeycombed aluminum compositions, the structures of foamed aluminum are used in the temperature range similar to solid aluminum.


Bismuth is a heavy, fragile and white crystalline trivalent metal with a pink shade. Chemically, bismuth is similar to arsenic and antimony. The chemical symbol for bismuth is ‘Bi’ with an atomic number of 83. Bismuth is also known as the most naturally diamagnetic metal among all others.

Bismuth is widely used in cosmetics and medical procedures. One of the major reasons behind the popularity of bismuth metal is the fact that bismuth is used as a substitute for the lead as lead is highly toxic. Therefore, bismuth has gain considerable commercial value over the last few years.


Brass is a kind of yellow allow usually made of copper and zinc and is widely used in musical instruments, rifle cartridges and cutlery. The alloy of brass which is low in zinc content, i.e. 30 percent of it is considered to have a good formability property and often refer to as cartridge brass. However, the alloy with rich zinc content shows good casting and machining properties.


Bronze is a type of metal which is hard, have good weather tolerance and good casting properties. It is basically a reddish alloy commonly used in church bells, canons, bearings and in casted sculptures. Copper has a major share in the alloying of bronze. Tin and nickel are some of the other alloying elements.


It is chemical element that has its chemical symbol as ‘Cd’ with atomic number 48 in the periodic table. Cadmium is a transition element that is soft, bluish-white and rare. It is believed that cadmium can cause cancer and normally found with the zinc ores. The major use of cadmium can be seen in batteries and pigments like plastic products.


Chromium is a metallic element that is commonly used in chromium plating for the purpose of decoration, corrosion and for wear protection. Chromium is also used as an alloying element in stainless steel. Unlike pure chromium which is ductile and mostly produced in laboratories, the commonly found chromium is hard and delicate at 700°C and above this temperature the element turns ductile. Similarly, chromium shows a good resistant against corrosion and oxidation at temperature of about 1100°C. This is possible because of the presence of resistant film on the surface.


Cobalt is a metallic chemical element that has its symbols as ‘Co’ in the periodic table. This hard, lustrous, silvery-gray metal occurs in variety of ores. Cobalt is normally used to prepare magnetic, wear resistant, high-strength alloys. The compounds of cobalt are used to produce ink, varnishes and paints.


Copper is a good conductor of electricity. It is red, slightly expensive and soft chemical element. It is widely used in the manufacturing of electric wires. Other than that it is also used in water pipes, roof plates, and in some old cooking appliances. In bronze (with tin) and brass (with zinc), copper is an important alloying element.


A yellow colored precious chemical element used in making coins, jewelry, decorative objects etc. In the periodic table, its symbol is Au (derived from Latin Aurum) and its atomic number is 79. For many centuries, this metal has remained in use as money. Gold is commonly found in rocks in the form of nuggets or lumps. It also occurs in veins under the surface of earth and also in alluvial (mud or sand deposits) deposits. It is compact, lustrous and has good properties of being malleable and ductile.

The most interesting fact of gold as metal is, it sets the monetary standards for both the International Monetary Fund (IMF) and the Bank for International Settlements (BIS). XAU is known to be the currency code of gold bullion (or bars).

Gold is both univalent and trivalent if we take it chemically. Although, gold is not known to react with other chemical elements, it still gets affected by chlorine, fluorine, aqua regia and cyanide. It makes mixtures of alloys when dissolves in mercury, but at no place it reacts with it. Unlike silver and base metals, gold is insoluble in nitric acid and that is the reason nitric acid has used for centuries to verify the gold presence in an object. This technique is also called ‘acid test’.

Cast Iron

Cast iron is a term used to refer to the family of alloys (ferrous alloys) made of iron, carbon about 2 to 4.5% and about 3.5% of silicon. Cast iron is available in several varieties.

If we talk about gray cast iron, it has low ductile properties, dampens vibrations and fragile. Carbon is found in the form of graphite flakes in gray cast iron. White cast iron is another variety of cast iron that is hard, possesses good resistant and is fragile. In white cast iron, the carbon is found in extremely hard ceramic particles known as cmentite.

Ductile iron as the name suggests shows good ductile properties. It is also shows good resistant against shocks. Ductile iron is formed by giving a heat treatment to gray cast iron. Malleable iron is another variety which is sturdy, shock resistant and ductile as well.


Lead is a soft, heavy metal mostly used in ship keels and in fishing nets sinkers to add weight. Another important use of lead can be seen where it is used as insulation next to radioactivity. Previously, lead was commonly used in roof windows and in shotguns. But as the poisonous and toxic properties of lead appeared on the scene, the use of lead discarded.


Magnesium is another important light, silver-white metallic chemical element that gives a bright white flame when burned. Magnesium is widely used in place of aluminum with a view to reduce weight. Magnesium is a reactive metal and commonly used in the manufacturing of car wheels and power saws.


Mercury, a poisonous silver liquid metal, widely used in thermometers and is also referred to as quicksilver. In the periodic table, it has its chemical symbol as ‘Hg’ (derived from Latinized Greek ‘hydrargyrum’ which means ‘watery or liquid silver’) and has an atomic number of 80. It is known to be one among other four elements (caesium, francium, and gallium, and the non-metal bromine) that take the liquid form at or near room temperature and pressure.

Other than thermometers, it is also used in barometers and several other scientific apparatus. Because of its toxic properties, its use in thermometers has greatly been reduced and is replaced by alcohol filled, digital and thermistor-based instruments. However, mercury thermometers still have a role to play in several different scientific research applications.

This metallic chemical element is found in deposits all over the world and is harmless in an insoluble form like in mercuric sulfide; however, it becomes toxic in soluble states like those of mercuric chloride or methylmercury.


A chemical element and a silver gray metal that is brittle and used in alloy steels. In the periodic table, it is represented by a symbol ‘Mo’ and has an atomic number 42. Among all the other elements, molybdenum is known to possess sixth highest melting point. This high melting point makes it useful for strong steel alloys. It is present in animals and plants in less amount and excessive presence can be poisonous in few animals. It was in 1778, when Carl Wilhelm Scheele discovered this element. It took three years before it was isolated by Peter Jacob Hjelm in 1781.

On the Pauling scale, it has an electro-negativity of 1.8 and an atomic mass of 59.9 g/mole. It is a transition metal that doesn’t react with oxygen or water, especially at room temperature. On higher temperatures, it forms the molybdenum trioxide by reacting with oxygen, i.e. given by the reaction: 2Mo+ 3O2 = 2MoO3.

It is one of the five elements having a high melting point, i.e. 2623°C. The other elements having high melting points are tantalum, osmium, rhenium and tungsten. It requires a temperature of over 600°C to burn.

By 4 May, 2007, its value was recorded as $65,000 per metric ton (or per tonne). From 1997 to 2007, its value remained $10,000. However, by June, 2005, the value of molybdenum reached $103,000 per metric ton or tonne.


Nickel is a hard silver-white metal that is used in the making of some types of steel or other alloys. Nickel coating is used on the surfaces for several different reasons such as for decorative purposes, erosion and corrosion resistant.

On higher temperatures, nickel alloys shows extremely excellent resistant against corrosion. Chromium, cobalt and molybdenum are some of the most commonly used alloying elements in nickel.

When it comes to nickel, it is strong, showing good resistant against corrosion and erosion and also robust. Nickel is widely used in stainless steel and other than that nickel alloys (superalloys) are commonly used in the preparation of appliances or equipments that work under immense temperatures such as engine components, rockets etc.


It is another chemical element which has its symbol ‘Pt’ in periodic table with atomic number 78. It is a silver-gray precious transition metal that is heavy, malleable and ductile. Platinum has good-resistant against the corrosion. It usually found in nickel and copper ores together with some other native deposits. It is widely used in automobile emission control devices, laboratory equipments, jewelry, dentistry and electrical contacts. ‘XPT’ is an ISO currency code used for platinum.


A chemical element has ‘Pd’ its chemical symbol in the periodic table and atomic number of 46. It is a rare silver-white transition metal that chemically looks like platinum. In 1803, it was discovered in platinum ores. It is given its name after the asteroid Pallas by William Hyde Wollaston.

It occurs as a free metal and afterwards alloyed with metals in platinum group. Palladium is used in different ways such as catalysis in catalytic converters in cars; on carbon it is used in organic chemistry and other similar chemical reactions. It is also used in the making of jewelry. ‘XPD’ is an ISO currency code for palladium.


Silver is a grayish-white precious metal represent by the symbol ‘Ag’ (derived from Latin ‘Agentum’) in periodic table and has an atomic number of 47. Being a metal, it possesses good thermal and electrical conductivity. Silver can be found as a free metal or in several minerals like argentite and chlorargyrite. Majority of the time, silver is obtained as a secondary product of copper, gold, lead, and zinc mining.

Since primitive people to present, silver has been used in one way or another. Being considered as a precious metal, it was used to make coins, currency, jewelry, cooking utensils, and ornaments. ‘XAG’ is an ISO currency code given to silver bullion.


Steel is a strong hard metal that is composed of a mixture of iron and about 2.1% of carbon. In order to make it more strong, the quantity of carbon contents are altered in the alloy, i.e. more the carbon contents in the alloy, stronger will be the metal. There are three standards of steel in respect to carbon, i.e. low carbon steel (having less than 0.3% carbon) is used in the manufacturing of nuts, bolts, sheets and tubes; Medium carbon steel (0.3-0.6% of carbon) is used in automotive and machinery equipments; and High carbon steel (over 0.6% of carbon) is known to be sturdy, tough, and erosion resistant used in the making of cutlery, springs, and cutting tools.

High Tensile Steel

High tensile steel is another metal which is ten times stronger than the tensile strength of wood and twice as stronger than mild steel. By increasing the tensile strength of the metal, the hardiness of metals is lessened. As a safety precaution, for large structures, the amount of acceptable stress is lowered.

Stainless Steel

Stainless steel is a kind of steel that is strong, hard, show good resistant against corrosion and ductile properties. Stainless steel is comprised of 11% of chromium, nickel and some other alloying elements. On exposure to oxygen, a hard thin layer develops on the surface that helps protect it against the corrosion. If you remove this thin layer, it will come back again. The strength of stainless steel depends on the carbon contents. Higher the carbon contents mean more strength, but lower resistant against corrosion.


Tantalum was previously known as tantalium. It is a chemical element that is hard and silver-gray in color. In the periodic table, it is represented as ‘Ta’ and has an atomic number of 73. This shiny transition metal shows good resistant against corrosion and is found in the mineral called tantalite.


It is another chemical element that is found in the sulfide ores. Chemically, it looks similar to tin, and is related to selenium and sulfur. It is lustrous silver-white element which is brittle, having ‘Te’ its symbol in periodic table with an atomic number of 52.


It is a soft silver-white metal that is usually used with other metals or used to cover them to avoid corrosion such as foot tins, casseroles etc. Below the room temperature, pure tin breaks apart into white powder called tin pest. In past, tin was used to make mugs, household plates and canclestics. Bismuth, antimon and lead are some alloying elements for tin.


It is a silver-white metal that is used to make different strong but lightweight materials. It is good against corrosion and keeps intact both in room and higher temperatures. It is for this reason, titanium is widely used in the application like aircrafts, jet-engines, racing cars, chemical and marine parts etc. aluminum, vanadium, and magnesium and molybdenum are some of the different alloying elements.


Among all the other metals, tungsten is known to have the highest melting point, i.e. 3410°C. This makes it a strong and hard metal. However, it is fragile, and shows poor resistant against corrosion. Tungsten along with its alloying elements is used in the applications demanding more than 1650°C of temperature such as nozzle of throat lines in missiles, hottest parts in jet and rocket engines. In incandescent bulbs, the filament wire is also made from pure tungsten using the powder technology.


It is a bluish-white metal which is inexpensive and has good weather proof properties. It is commonly used in the roofs and roof gutters. Before stainless steel, zinc was used to make kitchen utensils. Because of having low melting point and good casting properties, it is often preferred in materials where low strength is enough such as beer openers, door handles. Zinc along with copper is a vital alloying element in brass.


Types of Biotechnology

Since the evolution of primitive people, biotechnology has become much flourished by now. When the first human being realized that they could plant their own and new types of plants, crops, fruits and food, besides it they can breed their own animals with the help of biotechnology technique. With the help of this technique they can ferment the fruit juices into wine and milk could be converted into advance form like cheese or curd, or that beer could be made by fermenting solutions of malt and hops began the study of biotechnology. Once the first bakers got to know that they can make new and tastier food like soft, spongy bread instead of firm thin crackers, they were happy and behaving like amateur biotechnologists.

The term biotechnology raises many questions in the mind such as few think of producing new species of animals. Others might dream of numerous sources of drugs use for the therapy which doctors suggest as prescription of the therapy treatment. Still others think it as the possibility of growing new types of crops that are healthier for human beings. Literally, biotechnology is a term that is used to describe the process of using living organisms or products to alter human heath as well environment.

Artificial Insemination

Artificial insemination (AI) is an insemination process wherein sperm is unnaturally positioned into a woman’s cervix or uterus. During artificial insemination, ovarian kits, ultrasounds and blood tests are used to monitor the menstrual cycles of the woman. For the implantation of semen (liquid) it is washed in the laboratories as a result of which the chances of fertilization are increased during the process of removal of unimportant, potentially damage causing chemicals. The semen is inserted into the woman, and if the procedure is successful, she becomes pregnant.

Genetic Engineering

Genetic engineering is the use of different methods to operate the deoxyribonucleic acid (DNA) of cells to produce the biological products or to change the hereditary traits. Techniques used include using needles to insert DNA into an ovum, hybridomas (hybrid of cancer cells and of the cells that make the desired antibody) and the recombinant DNA, wherein the DNA of a desired gene is inserted into the DNA of bacterium, after that the bacterium multiplies itself, producing more of the desired gene. Other type is polymerase chain reaction (PCR) in which DNA quickly replicate to create a huge analyzable sample. The process makes perfect copies of DNA fragments and is used in DNA fingerprinting.


Cloning is a term used to refer to the creation of offspring by means of asexual reproduction. With the help of cloning, we can make identical copies of animals such as sheep, Dolly. When this technique was introduced scientist made the dolly sheep with the help of cloning in which they replace the nucleus with the other one and in this way we get the identical copies of animal. But it considered as an immoral activity which yet considered unethical for the cloning of human beings. However, there are several plants which have been produced through cloning over centuries.


Types of Ships

Galley:For many people, a ship is anything that is larger than a rowboat. However, in the eyes of sailors and pirates a ship in real sense is a term used for the vessels that fulfills certain criterions.

The ships are classified on the basis of the formation and arrange of the rigging (ropes and chains used to support and work the sails and masts of a ship). In order to qualify as a ship, the vessel should be square-rigged and must possess three masts with minimum of three stages of sails – course, topsail and t’gallant. Anything that doesn’t fulfill these criterions is considered as boat which is identified by its class names such as sloop, brig, xebec etc.

It is not simple to make a list of different types of ships under the same definition as the age of sail is based on four to five centuries including the Golden age of Piracy and the definition of different classes of the ships changed over a period of time. Even some classes of ships become extinct and new classes have taken the place of those old ones. Following are given some of the different types of ships that will help you understand the definition of different types of ships.

Schooner: It is relatively a small class of ships low on arms, i.e. carried only 6 guns. This class of ship used for about 300 years. It is found in both two mast and three mast varieties. Irrespective of the masts, schooners can be fore and/or aft rigged. Schooners are widely used in United States.

Sloop: Sloop is a class of ships with shallow draft which were used by pirates. It was equipped with small number of guns, i.e. 20 guns on one gun deck. Sloops were extremely fast ships which made them apt for the chases or pursuit.

Corvette: These are also referred to as Sloop of War. These were small and lightweight ships carrying a small amount of guns, to say 10 guns per ship. However, there were some Corvette types that were equipped with more guns. These were incredibly fast ships. It is yet not clear if pirates used them or not but it is obvious that these ships were given to privateers for being so fast.

Brig (and Brigantine): These ships were called brig because of the fact that these were used by the pirates or brigands. These were small but fast ships. In initial years, the term brigantine was used for any two-masted vessel that was sailed or rowed. Afterwards, the definition for the brig was refined and the term was restricted for certain type of ships. A brig was a square-rigged on its foremast and upper mainmast while the main sheet was rigged fore and aft on a gaff boom. A brig could carry 10 guns.

Barque (or Bark): The term barque is used for a ship with three or more masts. This term has been used in nautical terminology for quite along time. The term has changed its meaning over a period of time. During the 1400s, 1500s and 1600s, the term barque was used for the smaller merchant vessels. It was in 1700 when the Royal Navy used this term for a vessel that was comparatively different from its old ancestors. It was in 1800 when this term was associated with the ship having three or more masts with a certain rigging arrangement, i.e. square-rigged on fore and upper mainmasts and fore and aft on mizzen (rear mast).

Galleon: It was a ship built by the Spanish people and was commonly used between the 15th and 17th century by Spanish. Galleons served both as merchant ships and warships for many centuries. These are large, heavy ships which having a broad beam and are usually described by high fore and aft multi-deck castles. Apart from these high structures (castles), there were some large fo’c’sles as well which majorly affects the maneuvering abilities of the galleons. To overcome this problem, Spanish modified the design of these fo’c’sles in order to enhance the operating abilities of the galleons. However, they didn’t change the high castles at all.

Fluyt: It is a class of ships which is developed and used by the Dutch. The most distinguishing feature of this ship is its pear-shaped hull cross section which is narrower at the main deck but broadened out incredibly down to the waterline. It is said that at that time the taxes on the merchant ships were imposed on the basis of the area covered by the main deck and this pear shaped design helped reducing the main deck area while increasing the cargo area at the same time. Perhaps, keeping this fact in mind, the design of this ship was finalized. Fluyt were used in the European waters by the Dutch where Dutch East India Company was involved in trading activities.

Galley: Galley is a long flat ship with sails and used by ancient Greeks and Romans in wars. It is also the ship that was popular among the pirates of Mediterranean. Galley based on oars for propulsion. Galleys are more appreciated by the pirates of Mediterranean because of its ability to move faster in the smooth water conditions. It shows some good maneuvering features than the sailing ships as well. Galleys are not suitable for the rough waters such as Atlantic or English Channel. Similarly, Caribbean is also not suitable for the galleys, though they can still manage there but not that effective.

Merchantman: It is another class of ships that was used by pirates. We can found a lot description of these ships. These ships were in fact designed to carry massive cargos. Some varieties of merchantman were equipped with cannons whilst there were varieties without even a single weapon.


Types of Stars

A star is defined as a large ball of burning gas in space that we see as a tiny point of light in the sky at nighttime on the earth. There are numerous numbers of stars in the space which are classified into different types by astronomers. A star may range from a tiny brown dwarf to the supergiant. However, there are several other unusual types of stars found in the space like neutron stars and Wolf-Rayet stars.

What most of the people believe is that stars are the celestial bodies which are fixed and static. However, the great works of astronomers’ show that stars are intended to form, evolve and in the end exhaust their energy resources to become stellar remnant. Stars are actually characterized in terms of life cycle of stars and stellar evolution, though these are not living bodies.

Following are given some of the different types of stars with their brief description in terms of their energy resources:


A potostar is in fact a state prior to the formation of a star. A protostar is basically a group of gases that breakdown from a giant molecular cloud. In the stellar development, this protostar phase persists for over 100,000 years. With the passage of time, both the gravity and the pressure build up, compelling the protostar to breakdown or crash down. Gravitational energy is the sole contributor of heat generated in the protostar. At this stage, nuclear fusion reactions are not operational.

T Tauri Star

The phase before the main sequence star is known as T Tuari start. This stage of star formation and evolution lasts for about 100 million years. This stage arises when the protostar phase ends. Research shows that T Tauri stars don’t possess ample energy, pressure and temperature to initiate the nuclear fusion reactions. These stars normally possess large areas of sunspot coverage, intense X-ray flares and highly influential stellar winds. At this stage, these stars are similar to main sequence stars. Although, the amount of temperature is almost the same as that of main sequence stars, these are huge and brighter as well.

Main Sequence Star

Main sequence star accounts for most of the stars in our galaxy or even in universe. The most obvious example of such star is Sun. The other examples of main sequence stars are Sirius and Alpha Centauri A. Main sequence stars can be of varied size, mass and brightness, but all are performing the same function irrespective of their sizes, masses and brightness, i.e. transforming hydrogen into helium in their cores and le go huge amount of energy.

It is believed that a main sequence star is in a hydrostatic equilibrium position, i.e. the gravitational force drag the star inward while the pressure build up in response to fusion reactions push the star outward. These inward and outward forces balances the effect of each other and the star rests in a hydrostatic equilibrium. These forces help the star to keep its spherical shape intact.

The minimum mass limit of a main sequence stars is 0.08 times the mass of the Sun and 80 times the mass of the Jupiter. This is considered as the minimum amount of gravitational pressure that is essential to initiate the fusion process in the core of the star. Astronomers believe that main sequence star can grow over 100 times the mass of the Sun.

Red Giant Star

Once the stock of hydrogen is used up by the star the fusion reaction halts and the ability to generate an outward pressure weakens as a result of which the star is unable to keep the balance with the inward pressure. However, the crust of hydrogen surrounding the core continues to ignite the life in the star, but in the mean time also results in the drastic change of size. This growing star now takes the form of red giant star which is 100 times bigger than the size of the original main sequence star. After consumption of this hydrogen layer, helium and other elements take part in the ignition of fusion. When no more elements left in its core to initiate the fusion reactions, the red giant star transform into white dwarf star.

White Dwarf Star

Once the all the hydrogen, helium and other elements are eaten up, the red giant star takes the form of white dwarf star because of lessened mass limit. By this time, the fusion reactions completely stopped and the star breaks down inward against its own gravitational force. Although, there are no fusion reactions taking place on the star, it still shines. From now onwards, the white dwarf star begins to cool down and it takes it hundreds of billions years before it cools down. These numbers suggest that there is no white dwarf which is yet cooled down.

Red Dwarf Star

One of the most common types of stars in the universe is red dwarf star. Red dwarf stars are in fact main sequence stars but with relatively smaller in size (low mass) and much cooler as well. The best feature of these stars is their ability to preserve the hydrogen fuel for a longer period of time in their cores. Astronomers are of the view that there are red dwarf stars which can live up to 10 trillion years. According to the reports, the smallest red dwarf stars have 0.075 times the mass of the Sun, i.e. mass half of the mass of the Sun.

Neutron Stars

Astronomers are of the view that when a star is 1.35 and 2.1 times the mass of the Sun, it doesn’t turn into a white dwarf star rather a disastrous supernova explosion results in its destruction. The leftover mass becomes the neutron star. This star is made up of only neutrons and nothing else. Neutron stars come into existence because of the powerful gravity that smashes the protons and electrons to develop neutron. If the mass of the stars are even larger, they transform into black holes rather than becoming neutron stars.

Supergiant Stars

Supergiant stars are known to be the largest stars in the universe. These are gigantic with loads of mass, to say, about dozens of times the mass of the Sun. The Sun is assumed to be a very strong and firm that follows a significant process of hydrogen consumption. While supergiant stats are known to eat up their hydrogen fuel quite quickly and consumed up all of their fuel within few million years. Therefore, it is said that supergiant stars live a busy life and die young.

It often happens that the star has a large mass which even after the consumption of all the hydrogen fuel and other elements the mass leftover surpasses the limit that even neutron decadence couldn’t resist. Hence, the leftover material keeps creaking down inward and eventually gives rise to a black hole.

In black holes, all the mass gathers together at one place which results in massive gravitational force. These are given the name of black holes because even light cannot escape from them when they crossed event horizon. Event horizon is a place where escape velocity becomes equal to speed of light. Astronomers say that black holes are the bodies which cannot discharge light at any waveband and for this very fact they are hard to notice.

Electronic Commerce

Types of Electronic Commerce

Electronic commerce, also known as e-comm, e-commerce, eCommerce or even EC is a phenomenon used to refer to the system of distribution, selling, purchasing, marketing, and conditions for additional information of the products or services through the Internet, especially the World Wide Web. Also, sharing of information between different corporations is often included in e-commerce. E-commerce was first introduced in late 70s when it was merely used for the purpose of sending and receiving electronic documents, i.e. invoices. However, with the passage of time, the scope of e-commerce has now become broader and now it also deals with the buying and selling of goods and services through Internet. A newly coined term e-business is often used interchangeably for e-commerce.

E-commerce is classified into five major types which are given below:

Business to Consumer (B2C)

Business to Consumer or B2C is a type of e-commerce in which business and consumer is involved. In this model of e-commerce, the business sells its products or services to the consumer on Internet.

Business to Consumer is a kind of direct trade between business and consumer where a consumer buy a product or business sell a product directly. For example, whenever you want goods or services, you can buy it from the supplier’s website in a direct manner without being involved with any third party.

Business to Business (B2B)

Business to Business or B2B is a model in which buyer and seller are considered two different entities. It pretty much works like the one where manufacturer supply goods to the wholesaler or retailer. For instance, we all know about Dell that deals with computers and related accessories on the Internet. But there are number of accessories which are not manufactured by the Dell. So, Dell purchases those products from the businesses involved in the production of those accessories.

B2B is considered as one of the most cost effective model in the world of e-commerce.


  • Promotes your business on the Internet
  • Products import and export
  • Determine buyers and suppliers
  • Position trade guides

Consumer to Consumer (C2C)

Consumer to Consumer or C2C is a model that involves consumer to consumer online dealings. In this model a consumer need to use the services of online market dealer however, there are not major business are involved in this type of model. Here you are not dealing with any business firm rather dealing directly to other consumer through online market dealer such as eBay to make your transaction possible.


Mobile Commerce also known as m-commerce or mCommerce is a model that involves the use of mobile for making transactions. In this model, the consumers interact with one another through mobiles and conduct business.

Apart from above mentioned e-commerce models, there are several other e-commerce models as well such as Business to Employee (B2E), Government to Business (G2B) and Government to Citizen (G2C). These models are somehow related to the above mentioned models in several aspects.

Market Research

Types of Market Research

Market research is basically a procedure in which a systematic collection of data about any certain target market is made such as competitors, customers, market trends etc. The main purpose of conducting a market research is to get a detailed understanding of any certain market related subject. One major cause behind conducting a market research is the day by day increasing competition among different associations. Associations either conduct this market research by forming a team or they may take help from any of the market research consultancies or agencies to conduct market research the association’s behalf.

Market research has an important role to play in any type of business firm or organizations, especially for the organizations who are aiming to explore the market trends regarding the demand for their existing products and the products which they are planning to introduced in the market in order to boost their business profits. As market research is always objective oriented, you need to have your objectives and goals well-defined before conducting market research in one or another way.

Types of Market Research

Primary research and Secondary research are the two major ways to carry out the market research. The objectives you defined determine the selection of the type for carrying out a market research.

Primary Research

Primary research is a process in which systemic collection of data is done straight from the source. This means that if an organization is willing to know the demand of its certain product, a research will be conducted where the feedback is collected directly from the customers. Different ways are used to collect the feedback from the customers such as interviews, surveys, or group sessions etc. However, primary research is a time consuming as well as pricey. Primary research is further subcategorized into two different types, i.e. quantitative primary research and qualitative primary research.

Quantitative Primary Research: This type of primary research deals with collecting a numerical data through surveys. Market Research Survey is one of the most widely used quantitative method. Researchers then make an analysis on the basis of collected numerical data. The surveys under quantitative technique normally based on questionnaires. These questionnaires contain close ended questions and the numbers of questions in a questionnaire are fixed. These surveys are not time consuming as customer has to tick the selection of his/her choice on the questionnaire. The answers of the questions are normally excellent, very good, good or satisfactory. Researchers collect the data and analyzed it statistically before giving their conclusions. Different means are used to conduct these surveys, i.e. face to face with customers, through email, telephone, or through post.

Qualitative Primary Research: Qualitative primary research is a technique which focuses on interviews or group sessions for the collection of data. Unlike quantitative technique, this research technique focuses on open ended questions. In this sort of questioning technique, one is not required say yes or no or tick the relevant answer box instead it includes a detailed interviews or group sessions. An experienced executive is assigned a duty to interview one or more respondents. Different questions are asked to the respondents and data is collected that based on likes and dislikes, trends, requirements, emotional motivators of the market and of course feedback – positive or negative it may be. It is not necessary for experienced or trained executive to follow a certain format of questions. He/she can ask the questions in accordance with the situation at the time of interview. Unlike quantitative technique where respondents are only allowed to answer in yes or no, qualitative technique gives the respondents a freedom to express themselves freely.

Secondary Research

Secondary research is a type of market research in which the data collected has already been in compiled and organized form which is used to analyze things. In secondary research, the data is collected from different means such as government publications, libraries, Internet, magazines, chamber of commerce, trade associations etc. The collected data can either be in the form of charts, set of articles, research work, or demographic or statistical data. Different organizations make use of this data to understand the prevailing market conditions and scope of their products and services.

Chambers of Commerce: Organizations can collect information and data from the chambers of commerce regarding local firms and organizations.

Business Information Centers: Business information centers are another great source to gather data in the form of books, videos, publications etc.

Trade Associations: Trade associations are the best source to collect data regarding the industry leaders, trends, competitors etc.

Marketing Departments of Local Colleges: Organizations can also benefit from the research publications prepared by students on different projects.

Wholesalers and Manufacturers: Wholesalers and manufacturers are another great source to collect data based on customer’s likings and disliking, costs, complaints, etc.

Magazines and Newspapers: The best sources of gathering important data are through newspapers and magazines. The data collected from newspapers and magazines gives an important account for the market’s latest trends.

Competitors: Another way to gather crucial data is through conducting research regarding products and services of rival firms such as prices, brochures, marketing techniques used by them etc.

There are numerous other resources from where organizations can collect data easily, e.g. libraries, publications, books on different subjects, banks, real estate companies, and insurance companies. Qualitative research technique is far easier than the primary research technique. Also, qualitative technique is time efficient and cheaper than its counterpart. Apart from these positive points, there are some negative aspects as well with the qualitative research technique. For instance, in qualitative research technique, the data is mostly collected through different sources and one cannot be sure of its accuracy and authenticity because it is collected by other organizations or people in respect to their own demands and requirements. The data may be outdated and don’t serve the purpose for the respective organization or firm.

These are some of the different types of market research. Market research is an integral part of business firms and organizations because without conducting a proper market research, these firms cannot be able to understand the market trends and the customers bend (liking or disliking) towards certain products and services.  It is important of business firms to conduct market research to achieve their objectives.


Types of Adhesives

An adhesive is a substance that causes adhesion. In other words, we can say that an adhesive is a substance whose sole purpose is to provide a strong bond between two or more surfaces. Adhesives can either be structural or non-structural in nature. Structural adhesives are designed to hold up heavy loads while non-structural don’t meant for supporting heavy loads. Adhesives come in many different forms, e.g. they can be liquid, paste, granular, film, or fabric backed. Adhesives are also organic or non-organic.

Adhesives are used to join together different sort of materials. You can use adhesives for bonding plastic, wood, metal, stone, paper, and glass, ceramic and so on. However, an important point which you need to bear in mind is the selection of adhesive. This is really important as different materials require different type of adhesives to provide strong bond. For this reason adhesives are usually formed in a way to suit a particular material.

You will be surprised to know that there are over 10,000 different types of adhesives. Majority of the adhesives are used for household purposes. Adhesives used for residential applications are also of different types. Some are designed for general usage and other are designed for specific usage.

Adhesives become really handy when you are doing some repair work in home such as renovation or remodeling. It is important to have a good idea about different types of adhesives and their uses. Following are given some of the common types of adhesives along with their features and uses.

Acyrlic Adhesives: These are the adhesives which are designed for quick waterproof bonding on glass, metal and other household material. These adhesives come in liquid and powder part which are mixed together to form a paste which is then apply on the two surfaces which are required to be bonded. You can use different means to apply this paste on the surfaces such as brush wood strip, putty knife etc. Some of the popular brand names include Miracle Mender Glue, Devcon Plastic Sealer, 3 Ton Adhesive and Weather Ban Acrylic Sealant. Acetone, 3M Natural Cleaner and a citrus-based cleaner can be used to remove the adhesive.

Bolt-Locking Compound: As the name suggest, this is designed specially for locking bolts and screws threads to avoid leak, corrosion, looseness. Some of the popular brands are Scotch-Weld Epoxy Adhesive, Perma-Lok, Pronto Instant Bond and Loctite. These compounds are normally methacrylate-based liquids used prior to and subsequent to assembly.  You can remove this compound with warm, soapy water before it gets hard. Once it gets harden, you can use acetone.

Casein Glue: It is waterproof glue that is composed of skim milk and common chemicals. Conventionally, this glue is used to bond different parts of furniture together. It is still used to repair the antique furniture. This glue is extremely effective with oil woods such as teak and rosewood. However, this glue is more prone to fungus and mold. You can remove this glue with warm water.

Carpenter’s Glue:Some of the popular brands are Elmer’s Carpenter’s Glue and Titebond. Contrary to traditional white glues, these are yellow in color. The major difference between the white glue and yellow glue lies in their setting up time. Carpenter’s yellow glue set up the bond in one hour time while the white glue takes up to 8 hours to give strong bond. Carpenter’s glue is not waterproof. To have good results leave the surfaces intact for a night.

Cellulose Adhesive: Some of the popular brands include China Weld, Ambroid and Duco Cement. These are highly effective in bonding the pieces of china, glass, wood, model kits, and fabrics. These adhesives are water-resistant and are available in a tube or can form. It sets up the surfaces up to 60% strength within two hours, while maximum strength can be achieved in two days. Acetone or nail polish remove can be used to remove it.

Contact Cement: It is widely used for the surfaces where clamping is not workable such as fixing tiles or for laminated plastic countertop work. The popular brands are 3M Contact Cement, LePage’s Household Cement, Pres-Tite, and Elmer’s SAF-T. A roller or brush is used to apply a coat on the surfaces which need to be bonded. Then, the surfaces are allowed to dry for some time and then pressed against each other tightly. Acetone and 3M Natural Cleaner are good solvent.

Cyanoacrylate: These are water-resistant acrylic resins used to band the surfaces together in quick time. It sets up in just 30 seconds and strengthens in 30 minutes up to 12 hours depending on the nature of the surfaces. The popular brands are Super Glue, Krazy Glue and Wonder Bond Plus. It is effective for rubber, plastic, ceramics, vinyl and wood. It is preferred because of its quick strengthening time. However, care should be taken while using these adhesives as they can cause skin allergy or asthma if come in contact with the skin or inhaled. It can also affect the eyes as well. To remove, acetone is used.

Epoxy Glue: Epoxy glue is a type of adhesive used at surfaces where strong bonds are needed. These adhesives work well for glass, wood, plastics (some types), metal and stone. These are available in different forms, i.e. from flexible to rigid and from fast setting to slow setting. These adhesives are known to have high tolerance against heat and chemical. The most characteristic feature of these adhesives is their ability to bond two different materials together, e.g. aluminum to plexiglass. Epoxy adhesives come in two parts, i.e. epoxide ‘resin’ and polyamine ‘hardener’, which are mixed together to form a paste which is then applied to the surfaces which need to be bonded together. These are water-resistant and acetone is used to remove these adhesives. Some popular brands are Elmer’s Epoxy Glue, Scotch-Weld, Cold Cure Epoxy, and Super Glue Plastic Fusion Epoxy.

Hot Melt Glue: It is a kind of thermoplastic adhesive that is available in solid cylindrical sticks. These sticks are melted in an electric hot glue gun. It works well for leather, fabrics, ceramics tiles, furniture and carpeting. The most popular brands are Thermogrip and 3M Jet Melt. It is quite fast to set, to say in just 5 seconds and strengthen in about 1 minute. Acetone is used to remove this glue.

Liquid Solder: It works well for aluminum, iron, and other metals, especially to repair leakage and bonding sheet metal seams. However, this liquid soldering is not workable for electrical soldering. The major examples of liquid soldering include Permatex, Liquid Steel and Scotch-Seal Metal Sealant. It is available in both tube and can form. To achieve better results, make certain that both the surfaces are free from any dust or corrosion. It will take almost twenty-four hours to give strong bond.

Polyurethane Adhesives: These adhesives are water resistant and work well for both indoor and outdoor repair work. These can be used to bond wood, metal, drywall, concrete, painted surface, brick, fiberglass and ceramics. It is available in the market under the name Gorilla Glue or Excel. Whenever you use this adhesive, make this certain that the surfaces are properly clasped because this adhesive tend to expand during the settling process, eventually filling up the gaps and cracks. It takes six to twenty-four hours before curing up completely.

Polyvinyl Acetate: Commonly known as PVA glue or white glue, is conventional white glue used for residential applications such as ceramics, paper, woodwork etc. Popular brand names are as Elmer’s Glue-All, LePage’s Bondfast, GF Glue, Titebond Original Wood Glue, etc. It takes eight to twenty-four hours before it cures completely.

Resorcinol: This is a type of adhesive which is designed for woodworking. It also comes in two parts which are combined to make an adhesive paste which is then applied to wood surfaces to achieve strong bonds such as wooden boats, outdoor furniture etc. Popular brands are Weldwood Plastic Resin Glue, Scotchgrip Plastic Adhesive or AeroDux 500. It is important to take special care while dealing with such adhesives to avoid injuries.

Unmanned Satellites

Types of Space Vehicles

With the booming technological development in the recent few decades, man has now able to explore the space as well. Many different space vehicles and artificial satellites are invented for this purpose. Some of the different types of space vehicles and artificial satellites which are used by astronomers to explore the celestial bodies are given below:

Unmanned Satellites: Unmanned satellites are the satellites used by astronomers to explore the space are the one which are sent forth into the space and controlled by radio signals from the ground station. Most of the exploration work is carried out by these unmanned satellites. Some of the common examples of unmanned satellites are Vanguard, Voyager and Marine.

Manned Satellites: Unlike unmanned satellite, manned satellites are launched into space with astronauts who collect data and carry out different studies in space. Manned satellites allow the astronauts and cosmonauts to explore the space from space capsule. The Apollo spaceship is one of the most apt examples of this type of spacecrafts.

Space Station: A space station is basically a research centre in the space. Astronauts are taken to space in capsules and docked in the Skylab. Astronauts carry out different experiments and come back to earth leaving behind the Skylab in the orbit. It was in May 14, 1973 when the first Skylab was launched into the space. The three astronauts stayed there and brought back about 300,000 pictures of the sun in addition to the pictures of the comet Kohoutek, Conrad, Kerwin, and Weitz.

Shuttle Vehicles: Shuttle vehicles are the spacecrafts which take off from the earth like any ordinary aircraft and reach the space and stay in the orbit similar to satellites. Some of the popular shutter vehicles used by NASA include Discovery, Columbia and Challenger.

Artificial Satellites

Artificial satellites are divided into different types based on their designs and the purpose for which they are assumed to perform. Some of the different types are:

Scientific Satellites: Scientific satellites are the satellites used to collect data regarding radiations, earth magnetic field, earth shape, temperature in space, micrometeoroids etc. These satellites are equipped with several different instruments and devices which collect the data from the space and send it to the earth. Explorer, Vanguard, Discoverer and Monitor are popular scientific satellites.

Weather Satellites: As the name suggests, these satellites are used to collect information regarding weather. Tiros series is a good example of such satellites.

Communications Satellites: Communication satellites are the satellites used for transmitting radio signals, telecasts, telephone calls, teleprints and telephotos to far-off regions of the world. Some of the popular satellites are Score, Echo, Telstar, West Ford, Relay, Syncom, and Courier.

Navigation Satellites: Navigation satellites such as Transit series are used to broadcast special radio signals to the aircrafts and ships in any sort of weather conditions.

Space Probe Satellites: Space probe satellites are used to collect data from the space. For instance, the Mariner satellites are used to collect data from the Venus and Mars. Some other series include Pioneer series, Surveyor series, and Ranger series.


Types of Tornadoes

The term tornado is defined as a violent storm with very strong winds which move in a circle. Tornadoes are basically a vertical column of air which is narrower at the bottom and wider at the top with dense heavy clouds. A tornado revolves counterclockwise at a very high speed. All the true tornadoes have one characteristic in common that all of them appear to us like a condensed funnels. These funnels are surrounded by clouds of debris or dust. The swirl of a tornado is formed because of immense energy transformations.

Tornadoes are formed in several different shapes and sizes. A tornado can have shapes that range from a rope-like structure to fat cylinders or even in conical or wedge-shaped structures. Following are mentioned some of the different types of true tornadoes along with some cousins of tornadoes including, dust devil, gustnado and firewhirl. These are called cousins of tornadoes because of their structures.

Supercell Tornadoes

Supercell thunderstorms are accountable for giving rise to a number of most tremendous tornadoes. A supercell thunderstorm is normally a long-lasting thunderstorm having a constant spinning updraft of air within itself. These thunderstorms are pretty much capable of producing violent tornadoes with a huge wedge shaped structure. A low-hanging, rotating layer of cloud called wall cloud is produced with supercell thunderstorms. It has been noted that one side of the wall cloud is absolutely free of rain while the other has dense shafts of rain. The updraft air that is seen on the radar is given the name of mesocyclone.

Most of the tornadoes formed from supercell thunderstorms normally remain connected to the ground for fairly longer period of times, i.e. an hour or more. These tornadoes are vicious having winds surpassing 200 mph.


Landspout are the tornadoes which are lesser in their intensity than supercell tornadoes. These types of tornadoes usually do not represented by wall cloud or mesocyclone. Landspout can often be seen under the cumulonimbus or towering cumulus clouds. These are formed in the direction of the leading edge of rain-cooled downdraft air emerged from a thunderstorm called gust front.


Gustnado is a type of tornado which is weaker and usually persists for shorter period of time. They normally form in the direction of the gust front of a thunderstorm and looks like a temporary dust whirl or debris cloud.


These are the tornadoes which are formed over the water that is why these are called waterspout. There can be different factors involve in the formation of waterspout, i.e. some of them are formed from supercell thunderstorms, while other are formed from the weak thunderstorms or rapidly growing cumulus clouds. They are not violent and far less destructive with their fifty yard width. These tornadoes normally appear over the warm tropical ocean waters. Funnel is composed of freshwater droplets.

Following two are the cousins of the tornadoes:

Dust Devils

Dust devils are normally appeared in the hot, dry clear days on the desert or over dry land. Late morning or early afternoon of the hot sunny day often results in dust devils. Light desert breeze is responsible for triggering the whirlwinds with winds exceeding 70 mph. As these are not formed because of the thunderstorm, so they are not categorized as true tornadoes. Most of the dust devils are short lived, i.e. remain for few minutes; however, these can remain for longer periods of time as well. Though harmless at most of the times, they can blow the vehicles off and can harm your eyes by blowing dust into them.


Firewhirls are usually formed as a result of extreme heat produced by major forest fire or volcanic eruptions. These are called firewhirls because of having a tornado-like structure of spinning column of smoke or fire. In firewhirls, the winds normally exceed 100 mph. The other names given to firewhirls are firenadoes, fire, tornadoes, or fire devils.