MRI (Classical theory Magnetic resonance) Essay

MRI (Classical theory Magnetic resonance) - Essay Example n electromagnetic laws a nucleus spining around its own axis with an electric charge will cause a small magnetic moment (composed of spin and charge) (Donald W et al. 2010). The rotation (spin) of the nucleus is perpendicular to the axis of the nucleus magnetic field. In short, vector (Figure 1) is used to describe the magnitude (amplitude) and the direction of the magnetic moment (Westbrook, Roth & Talbot 2005). When the atomic mass number is odd an example is Na 23. Another example is 7Li. It has seven atomic mass number 3 protons and 4 neutrons and thus will give rise to an MR signal. The spin (I) for 23Na and 7Li will be 23⠁„2 and 3/2, respectively. For example, 14N has seven protons and seven neutrons (Z=7 and A=14). The spin (I) for 14N will be However, if the atomic number and atomic mass number are even, then there is no magnetic moment and thus no MR signal (for instance, 114Cd is composed of 48 protons plus 66 neutrons, Z=48 and A=114) (BROWN & SEMELKA 1999; Donald W et al. 2010). It is important to know that the vectors of the MR active nuclei in the absence of the main magnetic field will spin randomly; thus, the random directions of the nuclei will affect the magnitude of the net magnetic moment. The probability of the net magnetic moment approaching zero is when there are many nuclei aligned in different directions If RF pulse is applied at the resonance, then the protons can absorb that energy at the quantum level, a single proton jumps to higher energy state. At the macro or classical level, to an observer in the external laboratory frame of reference, the magnetization vector spiral down towards the xy plane. Now to see the behavior of the rotating frame when a RF pulse is applied from external source ,we keep this thing in minds that pulses are often labeled by their tip angle which can be any value of angle but most of the times the 90o and 180o. The tip angle is dependent on both the magnitude of the externally applied magnetic field and

Micro case Study Example | Topics and Well Written Essays - 500 words

Micro - Case Study Example Monopolies are given the rights to be the only firms in operation as a result of various barriers to entry into the industry. The major barriers are permits or licenses, ownership of key resources, copyrights and patents, high start up cost and being offered subsidies. Monopolies may also come across barriers in going out of the market, whereby they are restricted from exit from the market if they are responsible for producing an important product. (Musgrave et al, 41). If a government concludes that products manufactured or provided by such firms are indispensable for the benefit of citizens then such monopoly could be halted from exiting because it improves the living standards of people. Monopolies are also characterized by being in charge of technological knowhow used in production or information, which is not available to potential competitors. In addition to this, monopolistic enterprises might have some information or technology, which is not known to others. The technology or information may or may not be solely owned and it could even be a secret formula, which could be a unique way of producing the distinctive product, which will leave other firms in no position to produce the same The key source of a monopoly are the hurdles to entry, which originate from sources such as ownership of key resources and patents, whereby the government may give individual firms the exclusive rights to produce some products. Therefore, production costs will make the only producer more proficient compared to a large group of producers, which will be forced to go out of the market (Musgrave et al, 21). The government can regulate a monopoly so as to prevent heightened prices in a market, and this is achieved by setting the average price of products. The main drawback is that at times the regulated prices are below average the total costs incurred, which means that prices are lower than the producer’s average total costs, and in such cases, a firm