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The heart is a myogenic muscular organ found in all animals with a circulatory system (including all vertebrates ), that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology ) means "related to the heart" and comes from the Greek καρδιά, kardia , for "heart". The vertebrate heart is composed of cardiac muscle , which is an involuntary striated muscle tissue found only in this organ, and connective tissue . The average human heart , beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males. [ 1 ] In invertebrates that possess a circulatory system, the heart is typically a tube or small sac and pumps fluid that contains water and nutrients such as proteins , fats , and sugars . In insects , the "heart&quo

From Wikipedia, the free encyclopedia This article is about audible acoustic waves. For other uses, see  Sound (disambiguation) . In a  drum  sound is produced when its membrane vibrates Sound  is a  mechanical wave  that is an  oscillation  of  pressure  transmitted through a  solid ,  liquid , or  gas , composed of  frequencies  within the range of hearing and of a  level sufficiently strong  to be heard, or the sensation stimulated in organs of hearing by such vibrations. [ 1 ] Contents   [ hide ] 1   Propagation of sound 2   Perception of sound 3   Physics of sound 3.1   Longitudinal and transverse waves 3.2   Sound wave properties and characteristics 3.3   Speed of sound 3.4   Acoustics 3.5   Noise 4   Sound pressure level 5   Equipment for dealing with sound 6   Sound measurement 7   See also 8   References 9   External links Propagation of sound Sound is a sequence of waves of pressure that propagates through compressible media such as

Project Tiger  is a wildlife conservation movement initiated in  India  in 1973 to protect  tigers . The project aims at tiger conservation in specially constituted  tiger reserves  representative of various regions throughout India and strives to maintain viable populations of Bengal tigers in their natural environment. In 2008 there were more than 40 Project Tiger reserves covering an area over 37,761 km 2  (14,580 sq mi). Project Tiger helped to increase the population of these tigers from 1,200 in the 1970s to 3,500 in 1990s. However, a 2008 census held by the Government of India revealed that the tiger population had dropped to 1,411. Since then the government has pledged US$153 million to further fund the project, set-up a Tiger Protection Force to combat  poachers , and fund the relocation of up to 200,000 villagers to minimize human-tiger conflicts. The number of tigers in India's wild has gone up by 20%, according to the latest(2011) tiger census, which has surveyed

In 1909,  Soreson  devised a scale known as p H  scale on which the strength of acid solutions as well as basic solutions could be represented by making use of hydrogen ion concentration. Sorenson linked the hydrogen ion concentrations of acid and base solutions to the simple numbers 0 to 14 on the pH scale. pH of a solution is defined as the negative logarithm of the hydrogen ion concentration in moles per litre. Mathematically: pH = log 10 In pure water [H + ] = 1.0 x 10 -7 \ pH of pure (neutral) water = - log (10 -7 ) = 7 Thus, the pH value of pure water is equal to 7. Acid Solutions We know that all acidic solutions have H +  ion concentration greater than 1.0 x 10 -7 . The H +  ion concentration in an acidic solution may be 10 -5  , 10 -6 , 10 -4 , etc. Consider an acidic solution whose H +  ion concentration = 10 -6 \ Its pH = - log (H + ) = - log(10 -6 ) = 6 Clearly, pH values of all acidic solutions will be less than 7. Basic Solutions All basic solution

1.    What is an acid? Solution: An acid is a hydrogen-containing chemical compound which, when dissolved in water, gives hydrogen ion (H + ) or hydrated hydrogen ion (H 2 O. H + ) or hydronium ion (H 3 O + ).   2.    What are bases and alkalies? Solution: Oxides and hydroxides of metals and metal like radicals (e.g., NH4 +  ions) are called bases. Bases ionise to give OH -  ions in aqueous solution. Bases may be soluble or insoluble in water. The soluble bases are called alkalies. Thus all alkalies are bases but all bases are not alkalies. Examples NaOH and Cu (OH) 2  both are bases, but, since NaOH is soluble in water, it is an alkali. On the other hand, since Cu (OH) 2  is insoluble in water, it is not an alkali. Other examples of alkalies are KOH, Ca (OH) 2  and NH 4 OH.   3.    Define pH. Solution: pH of a given solution is the negative logarithm to the base 10 of the hydrogen ion concentration, [H + ] expressed in g ions/lit or moles/lit. Thus pH=- log1- [H + ].