Physical Chemistry Lab Report Example | Topics and Well Written Essays - 1750 words - 2

Physical Chemistry - Lab Report Example cent concentration is high, Heating of luminescent substance or if it is exposed to infrared radiation or an electric field this results causes the probability of no radiative transitions. This process is usually undesirable and very high requirement are therefore imposed on the purity of luminescents.phosphors which rapid quenching of luminescence occurs when the temperature is raised or when it is exposed to infrared radiation are also used. Varieties of molecular interactions can also result in quenching. Examples include excited-state reactions, molecular rearrangements, energy transfer, ground state complex formation and collisional quenching Quenching can occur due to optical properties of the sample. High optical densities or turbidity can also result in decreased fluorescence intensities. The trivial type of quenching may contain very little molecular information .quenching may occur without any permanent change in the molecules, for example with no photochemical reactions.in static quenching a complex if formed between the fluorophore and the quencher and the complex is nonfloures-cent.numerous application for quenching is as a result of the requirements of molecular contact, for example quenching measurements can reveal the accessibility of fluorophores to the quencher Both static and dynamic quenching requires molecular contact between the fluorophore and the quencher. Collisional quenching, the quencher must diffuse to the fluorophore during lifetime of the excited state. When in contact the fluorophore returns to the ground state, without emitting photons. For a static and dynamic quenching to occur the fluorophore and the quencher must be in contact. Requirement of molecular contact for quenching may result in the numerous applications of quenching. The mechanisms of quenching include: foster resonance energy transfer, exciplex, static quenching.in forster resonance energy transfer ,there are few distinct mechanisms by which energy can be

History of Social Thought Essay Example | Topics and Well Written Essays - 1750 words

History of Social Thought - Essay Example History of Social Thought Karl Marx is one of the most distinguished philosophers and intellectuals the world has ever produced. Social class is the division of groups and individuals living in a social establishment on the basis of political status, financial position, educational background and economic ranking. Having a keen observation and a comparative account of the ancient times civilizations, it appears crystal clear that all human societies, from the most prehistoric ones, belonging to the Paleolithic and Neolithic eras, to the most modern technological societies of contemporary times, have been socially stratified since ever. â€Å"From cradle to grave†, Cuber witnesses, â€Å"position in the stratification hierarchy is one of the most important facts circumscribing the formation of personality and the freedom of action of the person.† (1959: 432) Sociological researches also affirm the evidence of divergent socioeconomic classes in every culture and civilization even during the prehis toric times. â€Å"According to historical and archaeological records†, Tumin observes, â€Å"stratification was present even in the small wandering bands that characterized society in the earliest days of man. In such primitive conditions both age and sex in combination with physical strength must have been important criteria of stratification.†The most prominent aspect of the Marxian Theory of Social Class is the existence of conflict between divergent social classes.