Microcontroller Based DC Motor Speed Controller

Microcontroller Based DC Motor Speed Controller In this report I present a microcontroller based DC motor speed controller. DC motors play a vital role in most of the industrial areas. They are mainly used for the mechanical movements of physical applications such as media drives, power plants, lifts, elevators, conveyers, belt driven loads (printing press) etc. The controller implements the control strategy governing the load and motor characteristics. To match the load and motor, the input to the microcontroller is manipulated by the controller. The purpose of a motor speed controller is to capture a signal representing the demanded speed, and to drive the motor at that speed. The controller may or may not actually measure the speed of the motor. If it does, it is called a Feedback Speed Controller or Closed Loop Speed Controller, if not it is called an Open Loop Speed Controller. Feedback speed control is better, but more complicated, and may not be required for a simple circuit design. The former (closed loop) is implemented in the presented controller design. The subject arrangement consisted of a tachometer attached to the shaft of the motor. A controller design cannot be more accurate than methods aimed at measuring actual motor speed. This is readily attained by coupling the motor shaft with a tachometer. The tachometer output signal is converted to a dc voltage signal acceptable to the microcontroller. The microcontroller is programmed to drive the motor accomplishing the load requirement. The operation of dc motor was studied. Several types of motors and various control types were investigated. The project also intends to familiarize us with the efficiency of PIC in control systems. To evaluate the effectiveness of the controller, analysis will be conducted driving variable load while maintaining constant speed of the motor. The advantages of using microcontrollers to control dc motor were studied. INTRODUCTION 1.1 MOTOR An electric motor is an electromechanical device that converts electrical energy to mechanical energy. The mechanical energy can be used to perform work such as rotating a pump impeller, fan, blower, driving a compressor, lifting materials etc. It is estimated that about 70% of the total electrical load is accounted by motors only. 1.2 CLASSIFICATION OF MOTORS Electric Motors Alternating Current (AC) Motors Direct Current (DC) Motors Synchronous Induction Three-Phase Single-Phase Self Excited Separately Excited Series Shunt Compound FIG-1.1 classification of motors 1.3 AC MOTORS An AC motor is a motor that is driven by an alternating current. It consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field. 1.3.1 TYPES OF AC MOTORS There are two types of AC motors, depending on the type of rotor used. The first is the synchronous motor, which rotates exactly at the supply frequency or a sub multiple of the supply frequency. The magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet. The second type is the induction motor, which turns slightly slower than the supply frequency. The magnetic field on the rotor of this motor is created by an induced current. 1.3.2 TYPES OF INDUCTION MOTORS Squirrel-Cage Induction Motors The most simple and reliable of all electric motors. It is essentially a constant speed machine, which is adaptable for users under all but the most severe starting conditions. Requires little attention as there are no commutator or slip rings, yet operates with good efficiency. Wound-Rotor (Slip Ring) Induction motor It is used for constant speed-service requiring a heavier starting torque than is obtainable with squirrel cage type. Because of its lower starting current, this type is frequently used instead of the squirrel-cage type in larger sizes. These motors are also used for varying-speed-service. Speed varies with this load, so that they should not be used where constant speed at each adjustment is required, as for machine tools. Single Phase Induction Motors This motor is used mostly in small sizes, where polyphase current is not available. Characteristics are not as good as the polyphase motor and for size larger than 10 HP, the line disturbance is likely to be objectionable. These motors are commonly used for light starting and for running loads up to 1/3 HP Capacitor and repulsion types provide greater torque and are built in sizes up to 10 HP. Synchronous Motors Run at constant speed fixed by frequency of the system. Require direct current for excitation and have low starting torque. For large motor-generators sets, frequency changes, air compressors and similar apparatus which permits starting under a light load, for which they are generally used. These motors are used with considerable advantage, particularly on large power systems, because of their inherent ability to improve the power factor of the system. 1.4 DC MOTOR Direct-Current motors, as the name implies, use a direct-unidirectional current. A DC motor has three main components: Field pole. The interaction of two magnetic fields causes the rotation in a DC motor. The DC motor has field poles that are stationary and an armature that turns on bearings in the space between the field poles. A simple DC motor has two field poles: a north pole and a south pole. The magnetic lines of force extend across the opening between the poles from north to south. Armature. When current goes through the armature, it becomes an electromagnet. The armature, cylindrical in shape, is linked to a drive shaft in order to drive the load. The armature rotates in the magnetic field established by the poles, until the north and south poles of the magnets change location with respect to the armature. Once this happens, the current is reversed to switch the south and north poles of the armature. Commutator. This component is found mainly in DC motors. Its purpose is to overturn the direction of the electric current in the armature. The commutator also helps in the transmission of current between the armature and the power source. 1.4.1 OPERATION OF A DC MOTOR: When a dc motor is subject to dc voltage, the current flows through the armature coil. A wire carrying current also has a magnetic field around it. This magnetic field distorts the parallel magnetic field of stator to produce a force which causes the armature coil to turn. FIG-1.2 operation of motor Each coil of the armature is not only connected to the brushes but the brushes are connected first to one end and then to the other end of the coil. This commutating action is necessary to maintain the same direction of the current flow in the armature coils relative to the magnetic field lines in the field poles. The motor would never turn without commutation. FIG-1.3 cross section diagram of a motor 1.4.2 Types of Excitations There are two basic elements in a DC motor. The way in which these are connected results in various types of DC motors. SHUNT WOUND: The construction and principle of operation of a shunt motor is similar to any DC motor. This type of motor is called shunt because the field is in parallel or shunts the armature. The shunt field is directly connected in parallel with the armature circuit. Shunt windings require large number of turns to produce a strong magnetic field. SERIES WOUND: In a series wound motor, the field is connected in series with the armature. In this type, the speed tends to increase until the back EMF equals the impressed voltage. The EMF also decreases the current in the field and armature. As the field weakens more speed is required to maintain the counter EMF. Thus a series motor is used only where the load is attached e.g. A lift truck, an electric crane. Etc. COMPOUND WOUND: A compound motor has two field windings, the shunt field and series field. The shunt connected in parallel with the armature and the series field connected in series with the armature. The combination of both fields gives double advantages. It has a greater torque than the shunt motor due to the series field and fairly constant speed due to the series field winding. The compound motor has both shunt and series motor characteristics. These will be discussed along with their control techniques in the next chapter. 1.5 TACHOMETER A tachometer is an instrument that measures the rotational speed of the shaft of the motor. It functions in a similar fashion as compared to a speedometer on a car. It tells you the speed of the car. Similarly the tachometer is used to measure the motor speed. In a closed loop control system the information about the instantaneous state of the output is fed back and compared with the input and difference is used to modify the output in such manner as to achieve a desired condition. Similarly a tachometer is coupled to the shaft of the motor. Thus a signal representing the speed of the motor is produced. This signal is fed back to the input where it is compared to the speed command voltage. The error produced is actuated by the speed of the motor. In my designed controller the error actuating and motor control is achieved by programming the microcontroller. It is used to control the rotation of the motor. It senses the input and process it using the program burned in it and gives the required PWM output on the required port pins. This output controls the on/off time of the mosfet and thus controls the motor. This technique and mosfets will be discussed in the next chapter. As long as the speed command voltage is held constant, the motor will run at a proportional constant speed regardless of the mechanical load. The set speed control gives a dc voltage input, for example 12 volts for maximum speed and zero for stationary. This could be a potentiometer providing any voltage in a range from zero to +12 volts. The microcontroller (PIC) amplifies the difference between the two input voltages (tachometer and potentiometer) and the error is actuated. 1.6 MICROCONTROLLER (PIC) The name PIC initially referred to Programmable Interface Controller. Advantages of using PIC over other controlling devices for controlling the DC motor are given below: SPEED The execution of an instruction in PIC IC is very fast (in micro seconds) and can be changed by changing the oscillator frequency. One instruction generally takes 0.2 microseconds. COMPACT: The PIC IC will make the hardware circuitry compact. RISC PROCESSOR The instruction set consists of only 35 instructions. EPROM PROGRAM MEMORY Program can be modified and rewritten very easily. INBUILT HARDWARE SUPPORT Since PIC IC has inbuilt programmable timers, ports and interrupts, no extra hardware is needed. POWERFUL OUTPUT PIN CONTROL Output pins can be driven to high state, using a single instruction. The output pin can drive a load up to 25mA. INBUILT I/O PORTS EXPANSIONS This reduces the extra ICs which are needed for port expansion and port can be expanded very easily. INTEGRATION OF OPERATIONAL FEATURES Power on reset and brown/out protection ensures that the chip operates only when the supply voltage is within specification. A watchdog timer resets PIC if the chip ever malfunctions and deviates from its normal operation. The speed of motor is directly proportional to the DC voltage applied across its terminals. Hence, if we control the voltage applied across its terminal we actually control its speed. A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor i.e. The duty cycle of the wave controls motor speed. This wave is generated by the PIC. . CHAPTER 2. 2.1 DC SHUNT MOTOR FIG -2.3 Shunt windings require large number of turns to produce a strong magnetic field. This is because a small gauge wire cannot handle heavy currents. As a result, when voltage is applied, very little current flows through the shunt coil. The interaction of the magnetic fields between the one from armature and the one from shunt coil causes the motor to rotate. The speed can be controlled by varying the field strength or armature voltage. Current is supplied from the stationary housing to the rotating armature through commutator brushes arrangement. As the stator is stationary, power is applied directly to it. 2.1.2 SPEED CONTROL OF A DC SHUNT MOTOR This type of motor runs at a constant speed practically, regardless of the load. It is the type generally used in commercial practice. Speed of the shunt wound motors may be varied in two ways: First, by inserting resistance in series with the armature, thus decreasing speed (FIG ) And second, by inserting resistance in the field circuit. In this case the speed will vary with each change in load. This normally works with any controller setting i.e. it maintains constant speed despite variable load. Therefore, a shunt motor has proved its efficiency in adjustable speed service and loads requiring a low starting torque. 2.2 DC SERIES MOTOR In a series motor, the field winding (shunt field) is connected in series with the armature winding (A) as shown in the figure. The field current is therefore equal to the armature current. Speed is restricted to 5000 RPM It must be avoided to run a series motor with no load because the motor will accelerate uncontrollably. FIG-2.5 V = Supply voltage E = Generated e.m.f I = Supply current RA = Armature resistance RF = Field resistance 2.2.2 SPEED CONTROL OF A DC SERIES MOTOR The speed of a series motor depends almost entirely on the flux. The stronger the field flux, the lower the speed. Likewise, decrease in load current and therefore in field current and field flux causes an increase in speed. This can be achieved by adding a resistor in parallel with the series field winding. This causes the field current to decrease and the flux drops accordingly. This causes the motor speed to increase. The speed can be decreased by adding an external resistor in series with the armature and the field winding. This would cause a reduction in the armature supply voltage causing the motor speed to decrease. 2.3 DC COMPOUND MOTOR A DC compound motor is a combination of shunt and series motor. In a compound motor, the field winding (shunt field) is connected in parallel in series with the armature winding (A). For this reason this motor has a good starting torque and a stable speed. The higher the percentage of compounding (i.e. percentage of field winding connected in series), the higher the starting torque this motor can handle. For example, compounding of 40-50% makes the motor suitable for hoists and cranes, but standard compound motors (12%) are not. There are 2 major types of compound motors. These are given below: Cumulative compound motors Differential compound motors FIF-2.6 CUMULATIVE COMPOUND MOTOR FIG-2.7 DIFFERENTIAL COMPOUND MOTOR 2.3.2 SPEED CONTROL OF A COMPOUND MOTOR The speed of a compound motor can easily be controlled by changing the voltage supply to the motor. A solid state AC variable frequency motor drive can also be used to vary the speed of an AC motor. 2.4 PWM (PULSE WIDTH MODULATION) PWM, or Pulse Width Modulation, is a method of controlling the amount of power to a load without having to dissipate any power in the load driver. Imagine a 10W light bulb load supplied from a battery. In this case the battery supplies 10W of power, and the light bulb converts this 10W into light and heat. No power is lost anywhere else in the circuit. If we wanted to dim the light bulb, so it only absorbed 5W of power, we could place a resistor in series which absorbed 5W and then the light bulb could absorb the other 5W. This would work, but the power dissipated in the resistor not only makes it get very hot, but is wasted. The battery is still supplying 10W. An alternative way is to switch the light bulb on and off very quickly so that it is only on for half of the time. Then the average power taken by the light bulb is still only 5W, and the average power supplied by the battery is only supplying 5W also. If we wanted the bulb to take 6W, we could leave the switch on for a little longer than the time it was off, then a little more average power will be delivered to the bulb. This on-off switching is called PWM. The amount of power delivered to the load is proportional to the percentage of time that the load is switched on. Pulse-width modulation (PWM) or duty cycle variations are commonly used in speed control of dc motor. The duty cycle is defined as the percentage of digital high to digital low and digital high pulse-width during a PWM period. Thus by varying the pulse width, we can vary the average voltage across a DC motor and hence its speed In my presented controller design the PWM (Pulse Width Modulation) function of PIC is used for the electric current control to drive a motor. PWM can change the duty of the pulse to output into CCP1 by the data. The duty of the pulse of CCP1 is controlled in the voltage (the control voltage). When the control voltage is higher than the regulation value, the H level time of the CCP1 pulse is made long and the number of rotations of the motor is lowered. When the control voltage is lower than the regulation value, the H level time of the CCP1 pulse is made short and the number of rotations of the motor is raised. This mechanism will be discussed and elaborated in the next chapter. 2.5 MOSFETS The speed controller works by varying the average voltage sent to the motor. Imagine a light bulb with a switch. When you close the switch, the bulb goes on and is at full brightness, say 100 Watts. When you open the switch it goes off (0 Watts). Now if you close the switch for a fraction of a second, and then open it for the same amount of time, the filament wont have time to cool down and heat up, and you will just get an average glow of 50 Watts. This is how lamp dimmers work, and the same principle is used by speed controllers to drive a motor. When the switch is closed, the motor sees 12 Volts, and when it is open it sees 0 Volts. If the switch is open for the same amount of time as it is closed, the motor will see an average of 6 Volts, and will run more slowly accordingly. As the amount of time that the voltage is on increases compared with the amount of time that it is off, the average speed of the motor increases. This on-off switching is performed by power MOSFETs. A MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is a device that can turn very large currents on and off under the control of a low signal level voltage 2.5.1 TYPES OF MOSFETS. There are NPN type and PNP type as the semiconductor part. When no voltage is applied no electric current flows between the drain and the source. NPN type is called N-channel and PNP type is called P channel. An oxide film is put to the semiconductor of NPN or PNP and metal is put onto it as the gate. In case of NPN, the part of N is a source pole and a drain pole. In case of PNP, the part of P is the polar side. When positive voltage is applied to the gate of the N-channel MOS FET, the electrons of N-channel of source and drain are attracted to the gate and go into the P-channel semiconductor among both. With the movement of these electrons, it conditions itself like spans a bridge for electrons between drain and source. The size of this bridge is controlled by the voltage to apply to the gate. . This type (N CHANNEL) of mosfet is used in the presented controller. FIG 2.8 In case of P-channel MOS FET, the voltage is opposite but does similar operation. When negative voltage is applied to the gate of P-channel MOS FET, the holes of P-channel of source and drain are attracted to the gate and go into the N-channel semiconductor among both. With the movement of these holes, a bridge for holes is spanned and the electric current flows between drain and source. Transistor controls an output current by the input current. However, in case of FET, it controls an output current by input voltage (Electric field). The input current doesnt flow. To handle a MOS FET, needs attention because the oxidation insulation film is thin. This film is prone to the high voltage of the static electricity and so on. CHAPTER 3 The highlighted part in the figure represents the shaft which links the motor and the tachometer. The speed of the motor is directly proportional to the frequency of the tachometer. The dc voltage input is provided by the potentiometer. The microcontroller operates on a dc voltage. The output from the tachometer is a sine wave which has to be rectified in order to operate the pic. This is achieved using an F/V converter. The converter releases a dc logic signal which operates the pic. CIRCUIT EXPLANATION: The input voltage to the main motor is controlled by a potentiometer. This variable resistor could be adjusted manually to provide a 0-12 v input. This voltage sets the number of rotations of the main motor. The input voltage of PIC becomes low when bringing VR1 close to the side 1 and PIC increases the drive electric current of the motor. That is, the revolution of the motor rises. The input voltage of PIC becomes high when bringing VR1 close to the side 3 and PIC reduces the drive electric current of the motor. That is, the revolution of the motor slows down. Control voltage is defined as the feedback signal which is produced to rectify the error between the desired and controlled speed. This is provided by the tachometer in our case. The output from the tachometer is a sine wave which cannot operate the microcontroller to perform the programmed functions. This is converted to a dc voltage signal compatible with the pic microcontroller. This changed voltage is used to enable the CCP feature of the PIC resulting in motor drive. The CCP feature will be discussed in detail later in the chapter. The control voltage to PIC is thus governed by the fluctuations of the main motor. This control voltage (feedback signal) is directly proportional to the rotational speed of the motor. The PIC microcontroller is the brain of the circuit controlling all actions to be done and the output. PIC controls the electric drive current for the control voltage to become a regulation value. When the revolution of the motor slows down, i.e. control voltage goes down, the drive electric current of the motor is increased and number of rotations is raised. When the control voltage reaches a regulation value, a drive electric current at the point is held. When the number of rotations of the motor is high, i.e. the control voltage is high, the drive electric current of the motor is reduced and number of rotations is lowered D1 is used to protect PIC when the voltage of the detection motor is high. The voltage which is applied to the terminal of PIC is a maximum of +5V. This zener diode prevents the destruction of PIC when the speed detection voltage of the motor exceeds 5V. CCP FEATURE Capture, Compare and Pulse Width Modulation feature is abbreviated to form CCP. Capture This is the function to capture the 16 bits value of timer1 register when an event occurs on pin RC2/CCP1. This can be used for the measurement of the period time of the signal like the frequency counter and so on Compare Generate an interrupt, or change on output pin, when Timer 1 matches a pre-set comparison value PWM Create a re-configurable steady duty cycle square wave output at a user set frequency. The timer resource of the capture and compare is timer1 and the timer resource of PWM is timer2. The following steps should be taken when configuring the CCP module for PWM operation: Set the PWM period by writing to the PR2 register. PWM Period equals [(PR2+1)]*4Tosc*(timer 2 prescale value), and the resultant PWM frequency equals 1/ PWM_Period. Tosc stands for time period of the oscillations. Set the PWM duty cycle by writing to the CCPR1L register and CCP1X and CCP1Y bits of CCP1CON register. Duty Cycle is based on CCPRxL, most significant byte, and CCPxCON, least significant two bits. CCPRxL functions as a comparative value with timer 2 and a scaling factor to determine the number of counts of CCPx. PWM logic remains high, without considering CCPxCON. The two least significant bits, CCPxCON, determine the percentage of the maximum resolution the PWM duty cycle is extended. Make the CCP1 pin an output by clearing the TRISC. Set the TMR2 prescale value and enable Timer2 by writing to T2CON register. Configure the CCP1 module for PWM operation. PWM can change the duty of the pulse to output into CCP1 by the data. When the time period of the H level of the pulse of CCP1 is short, the time of ON (the L level) becomes long in TR2 which implies that the drive electric current of the motor increases. Oppositely, when the H level time of the pulse of CCP1 is long, the ON time of TR2 becomes short and the drive electric current of the motor decreases. The duty of the pulse of CCP1 is controlled by the control voltage (feedback signal) which was taken in with input circuit. When the control voltage is higher than the regulation value, the H level time of the CCP1 pulse is made long and the number of rotations of the motor is lowered. When the control voltage is lower than the regulation value, the H level time of the CCP1 pulse is made short and the number of rotations of the motor is raised. A three terminal regulator is used for getting the operate voltage for pic. PARTS PIC16F873 3 Terminal regulator ( 7805) Transistor for MOS FET drive ( 2SC1815 ) Power MOS FET ( 2SK3142 ) Zener diode ( RD5A ) IC socket Resonator Variable resistor for motor speed setting Resistors Capacitors Printed board VFC 320 (F/V CONV) Bipolar transistor 2N222 FURURE WORK: Dec: complete circuit design and order components. January: software design and circuit assembly February: Simulation and preparation of final report and presentation March: review and appendices April: submission.

Nursing Informatics Article Review

Article Review Number Two NRSG 115 October, 31, 2012 Article Review Number Two This article briefly summarizes informatics providing definitions for confusing terminology and what it means for the nursing profession. Nursing informatics is described as the union of nursing science, computer science, and information science. As advances in technology continue, nursing informatics increasingly plays a larger role in patient care and nursing practice (Manal, Shaben, & Allen, 2012).By encouraging proficiency in informatics, the authors believe that nurses can improve their knowledge base and confidence in their practice. This competency can lead to a higher quality of care and a safer work environment in the nursing profession (Manal et al. , 2012). Quote â€Å"However, choosing to ignore the technology does not address the challenges. On the contrary, nurses need to think about technology beyond skills mastery and critically examine how it impacts patient care and nursing practice† (Manal et al. , 2012, p. 14). You can read also Coronary Artery Disease Nursing Care PlanParaphrase Nurses should view technology as another tool that is important for the profession and patient care (Manal et al. , 2012, p. 14). Evaluation All three authors are registered nurses. Kelib is a candidate for a PhD and holds two masters; one in business administration and the other in nursing. The remaining authors, Allen and Shaben, both hold masters in nursing. As nurses, they understand the increasingly complex world of technology that is changing the nursing profession, and why it is important for nurses to be competent in it.Two of the nurses provided their email addresses in the article for those interested in being a part of the Informatics Specialty Practice Group for Alberta nurses, which leads me to believe that they are very involved and obviously up-to-date in the world of nursing informatics. This article was published in spring of 2012. I believe it is one of the most current articles on the subject. It doesn’t dive into the specifics of informatics which is a constantly evolving field. Instead it focuses on the importance of understanding what informatics is and why it is important in nursing practice.Since it is such a quick and generalized overview, I believe it is as relevant as it was 6 months ago. This article was geared towards registered nurses, particularly those that work in Canada. I also believe that this article is applicable to anyone in the nursing profession. I do think that this information is relevant to me as a student. It is a very simple article that presents to the reader a brief description of informatics in language I understand. This information provides me insight into the importance and impact that the evolving world of technology has on nursing.The authors quote a professional opinion from one reference and cite references throughout the text to support their conclusions. The first section of the article defines health informatics and terminology related to literacy. All the definitions and facts are cited and referenced. The second half of the article provides an expert opinion as to why informatics is important to nursing. This article uses eight references. Four of the references were published within the past 6 years and the other half dates back from 1996-2003.I do consider this bibliography useful because this article is such a brief overview of informatics and I would like to learn more. I realize how important informatics is to nursing practice and the reference list provides great resources to expand my knowledge on the subject. This article was found on the CINAHL database provided by the Renne Library website. I went under advanced search options and narrowed the search by selecting the box, first author is a nurse, and limited the date of publication to no later than five years ago.I entered informatics into the find box. I think this is an expert opinion article because it is not peer reviewed. It does not incl ude the required abstract, introduction, methods, results, and discussion section that research articles have. It does cite other research articles and papers related to informatics to provide evidence for their opinion. References Kleib, M. , Shaben, T. , & Allen, D. (2012). Lost in translation. Alberta RN, 68(1), 12-14. Retrieved from

Why Are We Ticklish The Scientific Explanation

The phenomenon of ticklishness has puzzled scientists and philosophers for decades. From social bonding to survival, researchers have offered a wide range of theories to explain this peculiar bodily quirk. Opposing Theories Charles Darwin  argued that the mechanism behind ticklishness is similar to the way we laugh in response to a funny joke. In both cases, he contended, one must be â€Å"light† state of mind in order to respond with laughter. Sir Francis Bacon made an opposing claim when he said on the subject of tickling,  Ã¢â‚¬Å"...[W]e see that men even in a grieved state of mind, yet cannot sometimes forbear laughing. The opposing theories of Darwin and Bacon reflect some of the contemporary conflicts that exist in research on tickling today. Tickling as Social Bonding Tickling may function as a form of social bonding, especially for a parent and child. University of Maryland neuroscientist Robert Provine, who considers ticklishness to be â€Å"one of the broadest and deepest subjects in science,†Ã‚  says that the laughter response to being tickled is activated within the first few months of life and that tickling as a form of play helps newborns connect with parents.   Its also possible that the horseplay and other games involving tickling help us hone our ability to defend ourselves — a kind of casual combat training. This view is supported by the fact that the regions of the body that happen to be most ticklish, such as the armpits, ribs, and inner thighs, are also areas that are particularly vulnerable to attack. Tickling as a Reflex Research into the physical response to tickling has led to conclusions that conflict with the social bonding hypothesis. The social bonding hypothesis really starts to fall apart when one considers those who find the experience of being tickled unpleasant. A study conducted by psychologists at the University of California in San Diego found that subjects can experience an equal degree of ticklishness regardless of whether they believe they are being tickled by a machine or a human. From these findings,  the authors drew the conclusion that being ticklish is more likely a reflex than anything else. If ticklishness is  a reflex, why can’t we tickle ourselves? Even Aristotle asked himself this question. Neuroscientists at  University College London used brain mapping  to study the impossibility of self-tickling. They determined that the region of the brain responsible for coordinating movements, known as the cerebellum, can read your intentions and even predict exactly where on the body an attempt to self-tickle will occur. This mental process prevents out the intended tickle effect. Types of Ticklishness Just as there is wide variation to where and the degree in which a person is ticklish, there are more than one type of tickle. Knismesis is the light, gentle tickling felt when someone runs a feather across the surface of the skin. It does not typically induce laughter and can be described as irritating and slightly itchy. Conversely, gargalesis is a more intense sensation triggered by aggressive tickling and usually provokes audible laughter and squirming. Gargalesis is the type of tickling used for play and other social interactions. Scientists speculate  that each type of tickle produces markedly different sensations because the signals are sent through separate nerve pathways. Ticklish Animals Humans are not the only animals with a tickle response. Experiments in rats  have shown that tickling rodents can trigger inaudible vocalizations that are akin to laughter. A closer measurement of their brain activity using electrodes even revealed where the rats are most ticklish: along the belly and the bottoms of the feet. However, the researchers found that the rats who were put in a stressful situation did not have the same response to being tickled, which suggests that Darwins light state of mind theory might not be totally off base. For the human population, the explanation for the tickle response remains elusive, tickling away at our curiosity.  Ã‚   Key Takeaways The phenomenon of ticklishness has not yet been conclusively explained. Multiple theories to explain the phenomenon exist, and research is ongoing.The social bonding theory suggests the tickle response developed to facilitate social bonding between parents and newborns. A similar theory posits that ticklishness is a self-defense instinct.The reflex theory states that the tickle response is a reflex that is not affected by identity of the tickler.There are two different types of tickle sensations: knismesis and gargalesis.  Other animals experience the tickle response, too. Scientists have found that rats emit an inaudible vocalization akin to laughter when they are tickled. Sources Bacon, Francis, and Basil Montagu.  The Works Of Francis Bacon, Lord Chancellor Of England. Murphy, 1887. Harris, Christine R., and Nicholas Christenfeld. Humour, Tickle, And The Darwin-Hecker Hypothesis.  Cognition Emotion, vol 11, no. 1, 1997, pp. 103-110. Harris, Christine. The Mystery Of Ticklish Laughter.  American Scientist, vol 87, no. 4, 1999, p. 344. Holmes, Bob.  Science: It’S The Tickle Not The Tickler.  New Scientist, 1997, https://www.newscientist.com/article/mg15320712-300-science-its-the-tickle-not-the-tickler/. Osterath,  Brigitte.  Playful rats reveal brain region that drives ticklishness.  Nature News, 2016. ​Provine, Robert R. Laughing, Tickling, And The Evolution Of Speech And Self.  Current Directions In Psychological Science, vol 13, no. 6, 2004, pp. 215-218.

Unhealthy Sport

Unhealthy Sport It is universally known that going in for sports is an important component of healthy life. Almost all the people who want to feel good and look attractive go in for this or that kind of sports. Apart from positive influence on physical state, sport activities also provoke the secretion of endorphin – hormone responsible for happiness. Thus, sport is healthy both physically and emotionally. Unfortunately, when going in for sport, some people start taking steroids – the hormones that are actually produced by our organism to fight stress and promote growth and muscles’ development. There are two main reasons why people make up their mind to do that. They either want to improve their sport performance or make their muscles look bigger, thus making their appearance more attractive. Actually, from the medical point of view, the ability of steroids to improve physical performance is quite questionable. Yes, they increase endurance and promote the growth of muscle mass, but is it really the main reason of success in sport? Steroids will not give you neither skills, nor experience or agility, so necessary for a good sportsman. Their positive effect on the appearance is more than doubtful as well. Very often instead of well shaped body steroids promote acne, greasy hair, red spots all over the body and bad breath. All the bad influence steroids have on a human body is worth a separate report. The least we can mention is heart and hormonal problems as well as persistent problems in the intimate sphere. Taking steroids can neutralize positive effects from going in for sports and destroy your body.

Primary Education Of Upper Class Children - 872 Words

Primary education of upper-class children in colonial days included reading, writing, basic math, poems, and prayers. Education was provided for white students only and was privately taught: the purpose was to prepare children for their eventual roles in plantation life. During this time while males studied advanced academic subjects, the females learned to assume the role of the mistress of a plantation. It was not until the 1840s that an organized system existed. Education reformers like Thomas Jefferson with the common school, John Dewey with progressive education and E.D Hirsch with cultural literacy, who with their contributions helped shape the educational system we have today. Thomas Jefferson, the â€Å"Man of the People,† is best known for drafting the Declaration of Independence, but he also wrote prolifically and prophetically about education. â€Å"If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be,† he wrote in a letter to a friend. Common school advocates like Jefferson worked to establish a free elementary education accessible to everyone and financed by public funds. Jefferson understood that freedom depends on self-government and that education contributes to both the knowledge and virtues that form a self-governing citizen. Jefferson sought to teach â€Å"all children of the state reading, writing, and common arithmetic.† Jefferson viewed this basic education as instrumental in securing â€Å"life, liberty, andShow MoreRelatedRace and Social Inequality in Education1382 Words   |  6 PagesMajor social institutions affect society, humanity, and prosperity in different ways. 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Tsunami and Love Canal Free Essays

A  tsunami  (‘harbor wave’) or  tidal wave  is a series of water waves (called a  tsunami wave train) caused by the displacement of a large volume of a body of water, usually an ocean, but can occur in  large lakes. Tsunamis are a frequent occurrence in Japan; approximately 195 events have been recorded. Due to the immense volumes of water and energy involved, tsunamis can devastate coastal regions. We will write a custom essay sample on Tsunami and Love Canal or any similar topic only for you Order Now Earthquakes,  volcanic eruptions  and other  underwater explosions  (including detonations of underwater  nuclear devices), landslides  and other  mass movements,  meteorite ocean impacts or similar impact events, and other disturbances above or below water all have the potential to generate a tsunami. The  Greek  historian  Thucydides  was the first to relate tsunami to  submarine earthquakes,  but understanding of tsunami’s nature remained slim until the 20th century and is the subject of ongoing research. Many early  geological,  geographical, and oceanographic  texts refer to tsunamis as â€Å"seismic sea waves. CHARACTERISTICS: While everyday  wind waves  have a  wavelength  (from crest to crest) of about 100  meters (330 ft) and a height of roughly 2  meters (6. 6 ft), a tsunami in the deep ocean has a wavelength of about 200  kilometers (120 mi). Such a wave travels at well over 800  kilometers per hour (500 mph), but d ue to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has amplitude of only about 1  meter (3. 3 ft). This makes tsunamis difficult to detect over deep water. Ships rarely notice their passage. As the tsunami approaches the coast and the waters become shallow,  wave shoaling  compresses the wave and its velocity slows below 80  kilometers per hour (50 mph). Its wavelength diminishes to less than 20  kilometers (12 mi) and its amplitude grows enormously, producing a distinctly visible wave. Since the wave still has such a long wavelength, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not break (like a  surf break), but rather appears like a fast moving  tidal bore. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami’s wave peak reaches the shore, the resulting temporary rise in sea level is termed ‘run up’. Run up is measured in meters above a reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run up. About 80% of tsunamis occur in the Pacific Ocean, but are possible wherever there are large bodies of water, including lakes. They are caused by earthquakes, landslides, volcanic explosions, and  bolides. GENERATION MECHANISMS: The principal generation mechanism (or cause) of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually attributed to earthquakes, landslides, volcanic eruptions, or more rarely by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity. It is important to note that  tides  do not play any part in the generation of tsunamis; hence referring to tsunamis as ‘tidal waves’ is inaccurate. Seismicity generated tsunamis Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when  thrust faults  associated with  convergent  or destructive  plate boundaries  move abruptly, resulting in water displacement, due to the vertical component of movement involved. Movement on normal faults will also cause displacement of the seabed, but the size of the largest of such events is normally too small to give rise to a significant tsunami. |[pic] |[pic] |[pic] |[pic] | |Drawing of  tectonic plate |Overriding plate bulges under |Plate slips, causing |The energy released produces | |boundary  before earthquake. |strain, causing tectonic uplift. |subsidence  and releasing energy |tsunami waves. | | | |into water. | Tsunamis have a small  amplitude  (wave height) offshore, and a very long  wavelength  (often hundreds of kilometers long), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300  millimeters (12 in) above the normal sea surface. They grow in height when they reach shallower water, in a  wave shoaling  process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, a magnitude-7. 8 (Richter scale)  earthqu ake  occurred near the  Aleutian Islands,  Alaska. It generated a tsunami which inundated  Hilo  on the island of Hawaii’s with a 14  meters (46 ft) high surge. The area where the  earthquake  occurred is where the  Pacific Ocean  floor is  subducting  (or being pushed downwards) under  Alaska. Examples of tsunami at locations away from  convergent boundaries  include  Storegga  about 8,000 years ago,  Grand Banks  1929,  Papua New Guinea  1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilized sediments, causing them to flow into the ocean and generate a tsunami. They dissipated before traveling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc. ) The  1960 Valdivia earthquake  (Mw  9. 5) (19:11 hrs UTC),  1964 Alaska earthquake  (Mw  9. 2), and  2004 Indian Ocean earthquake  (Mw  9. 2) (00:58:53 UTC) are recent examples of powerful mega thrust  earthquakes that generated tsunamis (known as  teletsunamis) that can cross entire oceans. Smaller (Mw  4. 2) earthquakes in Japan can trigger tsunamis (called  local  and regional tsunamis) that can only devastate nearby coasts, but can do so in only a few minutes. In the 1950s, it was discovered that larger tsunamis than had previously been believed possible could be caused by giant  landslides. These phenomena rapidly displace large water volumes, as energy from falling debris or expansion transfers to the water at a rate faster than the water can absorb. Their existence was confirmed in 1958, when a giant landslide in Lituya Bay,  Alaska, caused the highest wave ever recorded, which had a height of 524 meters (over 1700 feet). The wave didn’t travel far, as it struck land almost immediately. Two people fishing in the bay were killed, but another boat amazingly managed to ride the wave. Scientists named these waves  mega tsunami. Scientists discovered that extremely large landslides from volcanic island collapses can generate  mega tsunami that can travel trans-oceanic distances. SCALES OF INTENSITY AND MAGNITUDE: As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events. Intensity scales The first scales used routinely to measure the intensity of tsunami were the  Sieberg-Ambraseys scale, used in the  Mediterranean Sea  and the  Imamura-Iida intensity scale, used in the Pacific Ocean. The latter scale was modified by Soloviev, who calculated the Tsunami intensity  I  according to the formula [pic] Where  Hav  is the average wave height along the nearest coast. This scale, known as the  Soloviev-Imamura tsunami intensity scale, is used in the global tsunami catalogues compiled by the  NGDC/NOAA  and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. Magnitude scales The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty Loomis based on the potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the  tsunami magnitude scale  Mt, calculated from, [pic] where  h  is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance  R  from the epicenter,  a,  b  Ã‚  D  are constants used to make the Mt  scale match as closely as possible with the moment magnitude scale. WARNINGS AND PREDICTIONS: Drawbacks can serve as a brief warning. People who observe drawback (many survivors report an accompanying sucking sound), can survive only if they immediately run for high ground or seek the upper floors of nearby buildings. In 2004, ten-year old  Tilly Smith  of  Surrey,  England, was on  Maikhao beach  in  Phuket,  Thailand  with her parents and sister, and having learned about tsunamis recently in school, told her family that a tsunami might be imminent. Her parents warned others minutes before the wave arrived, saving dozens of lives. She credited her geography teacher, Andrew Kearney. In the  2004 Indian Ocean tsunami  drawback was not reported on the African coast or any other eastern coasts it reached. This was because the wave moved downwards on the eastern side of the fault line and upwards on the western side. The western pulse hit coastal Africa and other western areas. A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known. Geologists,  oceanographers, and seismologists  analyze each earthquake and based on many factors may or may not issue a tsunami warning. However, there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors that are attached to buoys. The sensors constantly monitor the pressure of the overlying water column. This is deduced through the calculation: [pic] Where, P  = the overlying  pressure  in Newton per meter square, ? = the  density  of the  seawater = 1. 1 x 103  kg/m3, g  = the  acceleration due to gravity = 9. 8 m/s2  and h  = the height of the water column in meters. Hence for a water column of 5,000 m depth the overlying pressure is equal to [pic] Or about 5500  tonnes-force  per square meter. Regions with a high tsunami risk typically use  tsunami warning systems  to warn the population before the wave reaches land. On the west coast of the United States, which is prone to Pacific Ocean tsunami, warning signs indicate evacuation routes. In Japan, the community is well-educated about earthquakes and tsunamis, and along the Japanese shorelines the tsunami warning signs are reminders of the natural hazards together with a network of warning sirens, typically at the top of the cliff of surroundings hills. The  Pacific Tsunami Warning System  is based in  Honolulu,  Hawaii. It monitors Pacific Ocean seismic activity. A sufficiently large earthquake magnitude and other information trigger a tsunami warning. While the seduction zones around the Pacific are seismically active, not all earthquakes generate tsunami. Computers assist in analyzing the tsunami risk of every earthquake that occurs in the Pacific Ocean and the adjoining land masses. |[pic] |[pic] |[pic] |[pic] | |Tsunami hazard sign |A tsunami warning sign on |The monument to the victims of |Tsunami memorial | |atBamfield,  British Columbia |a  seawall  in  Kamakura, Japan, |tsunami at Laupahoehoe,  Hawaii |inKanyakumari  beach | | |2004. | | | As a direct result of the Indian Ocean tsunami, a re-appraisal of the tsunami threat for all coastal areas is being undertaken by national governments and the United Nations Disaster Mitigation Committee. A tsunami warning system is being installed in the Indian Ocean. Computer models can predict tsunami arrival, usually within minutes of the arrival time. Bottom pressure sensors relay information in real time. Based on these pressure readings and other seismic information and the seafloor’s shape and coastal  topography, the models estimate the amplitude and surge height of the approaching tsunami. All Pacific Rim countries collaborate in the Tsunami Warning System and most regularly practice evacuation and other procedures. In Japan, such preparation is mandatory for government, local authorities, emergency services and the population. Some zoologists hypothesize that some animal species have an ability to sense subsonic  Rayleigh waves  from an earthquake or a tsunami. If correct, monitoring their behavior could provide advance warning of earthquakes, tsunami etc. However, the evidence is controversial and is not widely accepted. There are unsubstantiated claims about the Lisbon quake that some animals escaped to higher ground, while many other animals in the same areas drowned. The phenomenon was also noted by media sources in  Sri Lanka  in the  2004 Indian Ocean earthquake. [21][22]  It is possible that certain animals (e. g. ,  elephants) may have heard the sounds of the tsunami as it approached the coast. The elephants’ reaction was to move away from the approaching noise. By contrast, some humans went to the shore to investigate and many drowned as a result. It is not possible to prevent a tsunami. However, in some tsunami-prone countries some  earthquake engineering  measures have been taken to reduce the damage caused on shore. Japan  built many tsunami walls of up to 4. 5  metres (15 ft) to protect populated coastal areas. Other localities have built  floodgates  and channels to redirect the water from incoming tsunami. However, their effectiveness has been questioned, as tsunami often overtop the barriers. For instance, the  Okushiri, Hokkaido tsunami  which struck  Okushiri Island  of  Hokkaido  within two to five minutes of the  earthquake on July 12, 1993  created waves as much as 30  metres (100 ft) tall—as high as a 10-story building. The port town of Aonae was completely surrounded by a tsunami wall, but the waves washed right over the wall and destroyed all the wood-framed structures in the area. The wall may have succeeded in slowing down and moderating the height of the tsunami, but it did not prevent major destruction and loss of life. [23] Natural factors such as shoreline tree cover can mitigate tsunami effects. Some locations in the path of the 2004 Indian Ocean tsunami escaped almost unscathed because trees such as  coconut palms  and  mangroves  absorbed the tsunami’s energy. In one striking example, the village of  Naluvedapathy  in India’s  Tamil Nadu  region suffered only minimal damage and few deaths because the wave broke against a forest of 80,244 trees planted along the shoreline in 2002 in a bid to enter the  Guinness Book of Records. [24]  Environmentalists have suggested tree planting along tsunami-prone seacoasts. Trees require years to grow to a useful size, but such plantations could offer a much cheaper and longer-lasting means of tsunami mitigation than artificial barriers. The Love Canal chemical waste dump In 1920 Hooker Chemical had turned an area in Niagara Falls into a municipal and chemical disposal site. In 1953 the site was filled and relatively modern methods were applied to cover it. A thick layer of impermeable red clay sealed the dump, preventing chemicals from leaking out of the landfill. A city near the dumpsite wanted to buy it for urban expansion. Despite the warnings of Hooker the city eventually bought the site for the meager amount of 1 dollar. Hooker could not sell for more, because they did not want to earn money off a project so clearly unwise. The city began to dig to develop a sewer, damaging the red clay cap that covered the dumpsite below. Blocks of homes and a school were built and the neighborhood was named Love Canal. Love Canal seemed like a regular neighborhood. The only thing that distinguished this neighborhood from other was the strange odors that often hung in the air and an unusual seepage noticed by inhabitants in their basements and yards. Children in the neighborhood often fell ill. Love Canal families regularly experienced miscarriages and birth defects. Lois Gibbs, an activist, noticed the high occurrence of illness and birth defects in the area and started documenting it. In 1978 newspapers revealed the existence of the chemical waste dump in the Love Canal area and Lois Gibbs started petitioning for closing the school. In August 1978, the claim succeeded and the NYS Health Department ordered closing of the school when a child suffered from chemical poisoning. When Love Canal was researched over 130 pounds of the highly toxic carcinogenic TCDD, a form of dioxin, was discovered. The total of 20. 00 tons of waste present in the landfill appeared to contain more than 248 different species of chemicals. The waste mainly consisted of pesticide residues and chemical weapons research refuse. The chemicals had entered homes, sewers, yards and creeks and Gibbs decided it was time for the more than 900 families to be moved away from the location. Eventually President Carter provided funds to move all the families to a safer area. Hooker†™s parent company was sued and settled for 20 million dollars. Despite protests by Gibbs’s organization some of the houses in Love Canal went up for sale some 20 years later. The majority of the houses are on the market now and the neighborhood may become inhabited again after 20 years of abandonment. The houses in Love Canal are hard to sell, despite a renaming of the neighborhood. It suffered such a bad reputation after the incident that banks refused mortgages on the houses. None of the chemicals have been removed from the dumpsite. It has been resealed and the surrounding area was cleaned and declared safe. Hooker’s mother company paid an additional 230 million dollars to finance this cleanup. They are now responsible for the management of the dumpsite. Today, the Love Canal dumpsite is known as one of the major environmental disasters of the century. **** Love Canal is an abandoned canal in Niagara County, New York, where a huge amount of toxic waste was buried. The waste was composed of at least 300 different chemicals, totaling an estimated 20,000 metric tons. The existence of the waste was discovered in the 1970s when families living in homes subsequently built next to the site found chemical wastes seeping up through the ground into their basements, forcing them to eventually abandon their homes. Love Canal was used from the 1940s through the 1950s by the Hooker Chemical Company and the city of Niagara Falls, among others, to dispose of their hazardous and municipal wastes and other refuse. The canal was surrounded by clay and was thought at the time to be a safe place for disposal—and, in fact, burying chemicals in the canal was probably safer than many other methods and sites used for chemical disposal at the time. In 1953, the Niagara Falls Board of Education bought the land-fill for $1 and constructed an elementary school with playing fields on the site. Roads and sewer lines were added and, in the early 1970s, single-family homes were built adjacent to the site. Following a couple of heavy rains in the mid-1970s, the canal flooded and chemicals were observed on the surface of the site and in the basements of houses abutting the site. Newspaper coverage, investigations by the State of New York and by the U. S. Environmental Protection Agency, combined with pressure from the district’s U. S. congressional representative and outrage on the part of local residents, led to the declaration of a health emergency involving â€Å"great and imminent peril to the health of the general public. Ultimately, in August, 1978, a decision was made by Governor Hugh Carey, supported by the White House, to evacuate the residents and purchase 240 homes surrounding the site. Shortly thereafter, the residents of nearby homes that did not immediately abut the site also became concerned about their health and conducted a health survey that purported to show an increase in the occurrence of various diseases and problems such as birth defects and miscarriages, which were attributed to chemical exposures. A great controversy ensued over whether the observations were real or reflected normal rates of such problems, and whether chemical exposures had, in fact, occurred. Eventually, political pressure resulted in families being given an opportunity to leave and have their homes purchased by the State. About 70 homes remained occupied in 1989 by families who chose not to move. The controversy at Love Canal followed on the heels of the heightened awareness that occurred in the 1960s about environmental contamination, and it contributed to public and regulatory concern about hazardous wastes, waste disposal, and disclosure of such practices. Such concerns led Congress to pass the Resource Conservation and Recovery Act (RCRA) and the Toxic Substances Control Act (TSCA) in 1976, and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as the Superfund bill, in 1980. When CERCLA was passed, few were aware of the extent of the problem potentially created by years of inappropriate or inadequate hazardous waste disposal practices. Since implementing CERCLA, the U. S. Environmental Protection Agency has identified more than 40,000 potentially contaminated â€Å"Superfund† sites. The Gulf War In August 1990 Iraqi forces invaded Kuwait, starting the Gulf War in which an allegiance of 34 nations worldwide was involved. In January  1991  of the Gulf War, Iraqi forces committed two environmental disasters. The first was a major oil spill 16 kilometers off the shore of Kuwait by dumping oil from several tankers and opening the valves of an offshore terminal. The second was the setting fire to 650 oil wells in Kuwait. The apparent strategic goal of the action was to prevent a potential landing by US Marines. American air strikes on January 26 destroyed pipelines to prevent further spillage into the Gulf. This however seemed to make little difference. Approximately one million tons of crude oil was already lost to the environment, making this the largest oil spill of human history. In the spring of 1991, as many as 500 oil wells were still burning and the last oil well was not extinguished until a few months later, in November. The oil spills did considerable damage to life in the Persian Gulf (see picture). Several months after the spill, the poisoned waters killed 20. 000 seabirds and had caused severe damage to local marine flora and fauna. The fires in the oil wells caused immense amounts of soot and toxic fumes to enter the atmosphere. This had great effects on the health of the local population and biota for several years. The pollution also had a possible impact on local weather patterns. How to cite Tsunami and Love Canal, Papers Tsunami and Love Canal Free Essays A  tsunami  (‘harbor wave’) or  tidal wave  is a series of water waves (called a  tsunami wave train) caused by the displacement of a large volume of a body of water, usually an ocean, but can occur in  large lakes. Tsunamis are a frequent occurrence in Japan; approximately 195 events have been recorded. Due to the immense volumes of water and energy involved, tsunamis can devastate coastal regions. We will write a custom essay sample on Tsunami and Love Canal or any similar topic only for you Order Now Earthquakes,  volcanic eruptions  and other  underwater explosions  (including detonations of underwater  nuclear devices), landslides  and other  mass movements,  meteorite ocean impacts or similar impact events, and other disturbances above or below water all have the potential to generate a tsunami. The  Greek  historian  Thucydides  was the first to relate tsunami to  submarine earthquakes,  but understanding of tsunami’s nature remained slim until the 20th century and is the subject of ongoing research. Many early  geological,  geographical, and oceanographic  texts refer to tsunamis as â€Å"seismic sea waves. CHARACTERISTICS: While everyday  wind waves  have a  wavelength  (from crest to crest) of about 100  meters (330 ft) and a height of roughly 2  meters (6. 6 ft), a tsunami in the deep ocean has a wavelength of about 200  kilometers (120 mi). Such a wave travels at well over 800  kilometers per hour (500 mph), but d ue to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has amplitude of only about 1  meter (3. 3 ft). This makes tsunamis difficult to detect over deep water. Ships rarely notice their passage. As the tsunami approaches the coast and the waters become shallow,  wave shoaling  compresses the wave and its velocity slows below 80  kilometers per hour (50 mph). Its wavelength diminishes to less than 20  kilometers (12 mi) and its amplitude grows enormously, producing a distinctly visible wave. Since the wave still has such a long wavelength, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not break (like a  surf break), but rather appears like a fast moving  tidal bore. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami’s wave peak reaches the shore, the resulting temporary rise in sea level is termed ‘run up’. Run up is measured in meters above a reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run up. About 80% of tsunamis occur in the Pacific Ocean, but are possible wherever there are large bodies of water, including lakes. They are caused by earthquakes, landslides, volcanic explosions, and  bolides. GENERATION MECHANISMS: The principal generation mechanism (or cause) of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually attributed to earthquakes, landslides, volcanic eruptions, or more rarely by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity. It is important to note that  tides  do not play any part in the generation of tsunamis; hence referring to tsunamis as ‘tidal waves’ is inaccurate. Seismicity generated tsunamis Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when  thrust faults  associated with  convergent  or destructive  plate boundaries  move abruptly, resulting in water displacement, due to the vertical component of movement involved. Movement on normal faults will also cause displacement of the seabed, but the size of the largest of such events is normally too small to give rise to a significant tsunami. |[pic] |[pic] |[pic] |[pic] | |Drawing of  tectonic plate |Overriding plate bulges under |Plate slips, causing |The energy released produces | |boundary  before earthquake. |strain, causing tectonic uplift. |subsidence  and releasing energy |tsunami waves. | | | |into water. | Tsunamis have a small  amplitude  (wave height) offshore, and a very long  wavelength  (often hundreds of kilometers long), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300  millimeters (12 in) above the normal sea surface. They grow in height when they reach shallower water, in a  wave shoaling  process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, a magnitude-7. 8 (Richter scale)  earthqu ake  occurred near the  Aleutian Islands,  Alaska. It generated a tsunami which inundated  Hilo  on the island of Hawaii’s with a 14  meters (46 ft) high surge. The area where the  earthquake  occurred is where the  Pacific Ocean  floor is  subducting  (or being pushed downwards) under  Alaska. Examples of tsunami at locations away from  convergent boundaries  include  Storegga  about 8,000 years ago,  Grand Banks  1929,  Papua New Guinea  1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilized sediments, causing them to flow into the ocean and generate a tsunami. They dissipated before traveling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc. ) The  1960 Valdivia earthquake  (Mw  9. 5) (19:11 hrs UTC),  1964 Alaska earthquake  (Mw  9. 2), and  2004 Indian Ocean earthquake  (Mw  9. 2) (00:58:53 UTC) are recent examples of powerful mega thrust  earthquakes that generated tsunamis (known as  teletsunamis) that can cross entire oceans. Smaller (Mw  4. 2) earthquakes in Japan can trigger tsunamis (called  local  and regional tsunamis) that can only devastate nearby coasts, but can do so in only a few minutes. In the 1950s, it was discovered that larger tsunamis than had previously been believed possible could be caused by giant  landslides. These phenomena rapidly displace large water volumes, as energy from falling debris or expansion transfers to the water at a rate faster than the water can absorb. Their existence was confirmed in 1958, when a giant landslide in Lituya Bay,  Alaska, caused the highest wave ever recorded, which had a height of 524 meters (over 1700 feet). The wave didn’t travel far, as it struck land almost immediately. Two people fishing in the bay were killed, but another boat amazingly managed to ride the wave. Scientists named these waves  mega tsunami. Scientists discovered that extremely large landslides from volcanic island collapses can generate  mega tsunami that can travel trans-oceanic distances. SCALES OF INTENSITY AND MAGNITUDE: As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events. Intensity scales The first scales used routinely to measure the intensity of tsunami were the  Sieberg-Ambraseys scale, used in the  Mediterranean Sea  and the  Imamura-Iida intensity scale, used in the Pacific Ocean. The latter scale was modified by Soloviev, who calculated the Tsunami intensity  I  according to the formula [pic] Where  Hav  is the average wave height along the nearest coast. This scale, known as the  Soloviev-Imamura tsunami intensity scale, is used in the global tsunami catalogues compiled by the  NGDC/NOAA  and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. Magnitude scales The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty Loomis based on the potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the  tsunami magnitude scale  Mt, calculated from, [pic] where  h  is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance  R  from the epicenter,  a,  b  Ã‚  D  are constants used to make the Mt  scale match as closely as possible with the moment magnitude scale. WARNINGS AND PREDICTIONS: Drawbacks can serve as a brief warning. People who observe drawback (many survivors report an accompanying sucking sound), can survive only if they immediately run for high ground or seek the upper floors of nearby buildings. In 2004, ten-year old  Tilly Smith  of  Surrey,  England, was on  Maikhao beach  in  Phuket,  Thailand  with her parents and sister, and having learned about tsunamis recently in school, told her family that a tsunami might be imminent. Her parents warned others minutes before the wave arrived, saving dozens of lives. She credited her geography teacher, Andrew Kearney. In the  2004 Indian Ocean tsunami  drawback was not reported on the African coast or any other eastern coasts it reached. This was because the wave moved downwards on the eastern side of the fault line and upwards on the western side. The western pulse hit coastal Africa and other western areas. A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known. Geologists,  oceanographers, and seismologists  analyze each earthquake and based on many factors may or may not issue a tsunami warning. However, there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors that are attached to buoys. The sensors constantly monitor the pressure of the overlying water column. This is deduced through the calculation: [pic] Where, P  = the overlying  pressure  in Newton per meter square, ? = the  density  of the  seawater = 1. 1 x 103  kg/m3, g  = the  acceleration due to gravity = 9. 8 m/s2  and h  = the height of the water column in meters. Hence for a water column of 5,000 m depth the overlying pressure is equal to [pic] Or about 5500  tonnes-force  per square meter. Regions with a high tsunami risk typically use  tsunami warning systems  to warn the population before the wave reaches land. On the west coast of the United States, which is prone to Pacific Ocean tsunami, warning signs indicate evacuation routes. In Japan, the community is well-educated about earthquakes and tsunamis, and along the Japanese shorelines the tsunami warning signs are reminders of the natural hazards together with a network of warning sirens, typically at the top of the cliff of surroundings hills. The  Pacific Tsunami Warning System  is based in  Honolulu,  Hawaii. It monitors Pacific Ocean seismic activity. A sufficiently large earthquake magnitude and other information trigger a tsunami warning. While the seduction zones around the Pacific are seismically active, not all earthquakes generate tsunami. Computers assist in analyzing the tsunami risk of every earthquake that occurs in the Pacific Ocean and the adjoining land masses. |[pic] |[pic] |[pic] |[pic] | |Tsunami hazard sign |A tsunami warning sign on |The monument to the victims of |Tsunami memorial | |atBamfield,  British Columbia |a  seawall  in  Kamakura, Japan, |tsunami at Laupahoehoe,  Hawaii |inKanyakumari  beach | | |2004. | | | As a direct result of the Indian Ocean tsunami, a re-appraisal of the tsunami threat for all coastal areas is being undertaken by national governments and the United Nations Disaster Mitigation Committee. A tsunami warning system is being installed in the Indian Ocean. Computer models can predict tsunami arrival, usually within minutes of the arrival time. Bottom pressure sensors relay information in real time. Based on these pressure readings and other seismic information and the seafloor’s shape and coastal  topography, the models estimate the amplitude and surge height of the approaching tsunami. All Pacific Rim countries collaborate in the Tsunami Warning System and most regularly practice evacuation and other procedures. In Japan, such preparation is mandatory for government, local authorities, emergency services and the population. Some zoologists hypothesize that some animal species have an ability to sense subsonic  Rayleigh waves  from an earthquake or a tsunami. If correct, monitoring their behavior could provide advance warning of earthquakes, tsunami etc. However, the evidence is controversial and is not widely accepted. There are unsubstantiated claims about the Lisbon quake that some animals escaped to higher ground, while many other animals in the same areas drowned. The phenomenon was also noted by media sources in  Sri Lanka  in the  2004 Indian Ocean earthquake. [21][22]  It is possible that certain animals (e. g. ,  elephants) may have heard the sounds of the tsunami as it approached the coast. The elephants’ reaction was to move away from the approaching noise. By contrast, some humans went to the shore to investigate and many drowned as a result. It is not possible to prevent a tsunami. However, in some tsunami-prone countries some  earthquake engineering  measures have been taken to reduce the damage caused on shore. Japan  built many tsunami walls of up to 4. 5  metres (15 ft) to protect populated coastal areas. Other localities have built  floodgates  and channels to redirect the water from incoming tsunami. However, their effectiveness has been questioned, as tsunami often overtop the barriers. For instance, the  Okushiri, Hokkaido tsunami  which struck  Okushiri Island  of  Hokkaido  within two to five minutes of the  earthquake on July 12, 1993  created waves as much as 30  metres (100 ft) tall—as high as a 10-story building. The port town of Aonae was completely surrounded by a tsunami wall, but the waves washed right over the wall and destroyed all the wood-framed structures in the area. The wall may have succeeded in slowing down and moderating the height of the tsunami, but it did not prevent major destruction and loss of life. [23] Natural factors such as shoreline tree cover can mitigate tsunami effects. Some locations in the path of the 2004 Indian Ocean tsunami escaped almost unscathed because trees such as  coconut palms  and  mangroves  absorbed the tsunami’s energy. In one striking example, the village of  Naluvedapathy  in India’s  Tamil Nadu  region suffered only minimal damage and few deaths because the wave broke against a forest of 80,244 trees planted along the shoreline in 2002 in a bid to enter the  Guinness Book of Records. [24]  Environmentalists have suggested tree planting along tsunami-prone seacoasts. Trees require years to grow to a useful size, but such plantations could offer a much cheaper and longer-lasting means of tsunami mitigation than artificial barriers. The Love Canal chemical waste dump In 1920 Hooker Chemical had turned an area in Niagara Falls into a municipal and chemical disposal site. In 1953 the site was filled and relatively modern methods were applied to cover it. A thick layer of impermeable red clay sealed the dump, preventing chemicals from leaking out of the landfill. A city near the dumpsite wanted to buy it for urban expansion. Despite the warnings of Hooker the city eventually bought the site for the meager amount of 1 dollar. Hooker could not sell for more, because they did not want to earn money off a project so clearly unwise. The city began to dig to develop a sewer, damaging the red clay cap that covered the dumpsite below. Blocks of homes and a school were built and the neighborhood was named Love Canal. Love Canal seemed like a regular neighborhood. The only thing that distinguished this neighborhood from other was the strange odors that often hung in the air and an unusual seepage noticed by inhabitants in their basements and yards. Children in the neighborhood often fell ill. Love Canal families regularly experienced miscarriages and birth defects. Lois Gibbs, an activist, noticed the high occurrence of illness and birth defects in the area and started documenting it. In 1978 newspapers revealed the existence of the chemical waste dump in the Love Canal area and Lois Gibbs started petitioning for closing the school. In August 1978, the claim succeeded and the NYS Health Department ordered closing of the school when a child suffered from chemical poisoning. When Love Canal was researched over 130 pounds of the highly toxic carcinogenic TCDD, a form of dioxin, was discovered. The total of 20. 00 tons of waste present in the landfill appeared to contain more than 248 different species of chemicals. The waste mainly consisted of pesticide residues and chemical weapons research refuse. The chemicals had entered homes, sewers, yards and creeks and Gibbs decided it was time for the more than 900 families to be moved away from the location. Eventually President Carter provided funds to move all the families to a safer area. Hooker†™s parent company was sued and settled for 20 million dollars. Despite protests by Gibbs’s organization some of the houses in Love Canal went up for sale some 20 years later. The majority of the houses are on the market now and the neighborhood may become inhabited again after 20 years of abandonment. The houses in Love Canal are hard to sell, despite a renaming of the neighborhood. It suffered such a bad reputation after the incident that banks refused mortgages on the houses. None of the chemicals have been removed from the dumpsite. It has been resealed and the surrounding area was cleaned and declared safe. Hooker’s mother company paid an additional 230 million dollars to finance this cleanup. They are now responsible for the management of the dumpsite. Today, the Love Canal dumpsite is known as one of the major environmental disasters of the century. **** Love Canal is an abandoned canal in Niagara County, New York, where a huge amount of toxic waste was buried. The waste was composed of at least 300 different chemicals, totaling an estimated 20,000 metric tons. The existence of the waste was discovered in the 1970s when families living in homes subsequently built next to the site found chemical wastes seeping up through the ground into their basements, forcing them to eventually abandon their homes. Love Canal was used from the 1940s through the 1950s by the Hooker Chemical Company and the city of Niagara Falls, among others, to dispose of their hazardous and municipal wastes and other refuse. The canal was surrounded by clay and was thought at the time to be a safe place for disposal—and, in fact, burying chemicals in the canal was probably safer than many other methods and sites used for chemical disposal at the time. In 1953, the Niagara Falls Board of Education bought the land-fill for $1 and constructed an elementary school with playing fields on the site. Roads and sewer lines were added and, in the early 1970s, single-family homes were built adjacent to the site. Following a couple of heavy rains in the mid-1970s, the canal flooded and chemicals were observed on the surface of the site and in the basements of houses abutting the site. Newspaper coverage, investigations by the State of New York and by the U. S. Environmental Protection Agency, combined with pressure from the district’s U. S. congressional representative and outrage on the part of local residents, led to the declaration of a health emergency involving â€Å"great and imminent peril to the health of the general public. Ultimately, in August, 1978, a decision was made by Governor Hugh Carey, supported by the White House, to evacuate the residents and purchase 240 homes surrounding the site. Shortly thereafter, the residents of nearby homes that did not immediately abut the site also became concerned about their health and conducted a health survey that purported to show an increase in the occurrence of various diseases and problems such as birth defects and miscarriages, which were attributed to chemical exposures. A great controversy ensued over whether the observations were real or reflected normal rates of such problems, and whether chemical exposures had, in fact, occurred. Eventually, political pressure resulted in families being given an opportunity to leave and have their homes purchased by the State. About 70 homes remained occupied in 1989 by families who chose not to move. The controversy at Love Canal followed on the heels of the heightened awareness that occurred in the 1960s about environmental contamination, and it contributed to public and regulatory concern about hazardous wastes, waste disposal, and disclosure of such practices. Such concerns led Congress to pass the Resource Conservation and Recovery Act (RCRA) and the Toxic Substances Control Act (TSCA) in 1976, and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as the Superfund bill, in 1980. When CERCLA was passed, few were aware of the extent of the problem potentially created by years of inappropriate or inadequate hazardous waste disposal practices. Since implementing CERCLA, the U. S. Environmental Protection Agency has identified more than 40,000 potentially contaminated â€Å"Superfund† sites. The Gulf War In August 1990 Iraqi forces invaded Kuwait, starting the Gulf War in which an allegiance of 34 nations worldwide was involved. In January  1991  of the Gulf War, Iraqi forces committed two environmental disasters. The first was a major oil spill 16 kilometers off the shore of Kuwait by dumping oil from several tankers and opening the valves of an offshore terminal. The second was the setting fire to 650 oil wells in Kuwait. The apparent strategic goal of the action was to prevent a potential landing by US Marines. American air strikes on January 26 destroyed pipelines to prevent further spillage into the Gulf. This however seemed to make little difference. Approximately one million tons of crude oil was already lost to the environment, making this the largest oil spill of human history. In the spring of 1991, as many as 500 oil wells were still burning and the last oil well was not extinguished until a few months later, in November. The oil spills did considerable damage to life in the Persian Gulf (see picture). Several months after the spill, the poisoned waters killed 20. 000 seabirds and had caused severe damage to local marine flora and fauna. The fires in the oil wells caused immense amounts of soot and toxic fumes to enter the atmosphere. This had great effects on the health of the local population and biota for several years. The pollution also had a possible impact on local weather patterns. How to cite Tsunami and Love Canal, Papers

Dancing at Lughnasa Essay Example For Students

Dancing at Lughnasa Essay Dancing at Lughnasa, a play written by Brian Frier, is a depiction of a mans memory of his childhood. The narrator, Michael, takes us back to the warm harvest days of August 1936, when he was a seven-year-old boy being brought up by his unmarried mother Chris and her four sisters. The play, through Michaels narration, touches on different aspects of life of the characters by exploring the occurrence of simple events which contribute an impact to their relationships. However, Michael, as a chorus figure, plays the most significant role which affects our perception of the events which unfold. The play opens up with Michaels first speech. When I cast back my mind to that summer of 1936- We see an apparent reflection of the memory through his language. This phrase is repeatedly mentioned in his first speech which reinforces the notion of reminiscing the past. On the other hand, we see as well how Frier distances Michael from the past events through a careful use of words. The word cast in his the first phrase gives an impression that he is trying to detach his memory from him and when he say cast back, it implies how he retraces back his memory without taking part in the past events. He is recollecting the past but not re-living it. This is evidently conveyed by the author for his main purpose of using Michael is as an observer of the present who oversees and judges the lives of the characters from the past. Therefore we see a sort of detachment and distancing of this personage from the events that he is recollecting. Through this technique, Michael appears like an omniscient narrator (although he is not) and this gives an impression that we are discovering the characters and the events at the same as the narrator. Although Michael is involved in these events, the narrative point of view could be qualified as a third-person limited. Frier doesnt really give him an access to the characters thoughts or to what they do in private since he only re-tells a story that he witnessed when he was a child. This method is important because it allows the narrator to assess the events in an adults point of view and this is one of his main functions as a chorus-figure which we will explore later on. Another remarkable linguistic aspect of this speech is that it is characterised by a lyrical tone. The choice of this tonality is important in order to remind us of the notion of musicality and the idea of dance. The tone is very comforting but at the same time it creates a nostalgic atmosphere and the tone itself seems to distance us from the characters being introduced. Frier applies the flashback technique by using Michaels memory to simply separate two elements of his character he detaches the adult Michael from Michael the boy. This explains why the whole play has no plot at all. The narrator relates a story of what he witnessed when he was seven therefore he is relating his memory in an objective manner which simply imply that during that summer of 1936, he did not really have a complete and a deeper understanding of those events. He is narrating a story according to how things had happened exteriorly. This explains as well his absence throughout the play for the reason that he hides and observe everybody as if it is his main preoccupation. for the first time in my life I had a chance to observe him(his father), It had fallen out of Aunt Kates prayer book and she snatched it from me before I could study it in detail. Since the play echoes Michaels memory as a boy, this answers the flatness of the plot. There is no climax in the play and it almost lacks colour and other ingredients that could make the story attractive. This parallels to the boys innocence which is a barrier that separates him from the interior side of the characters. There is nothing spectacular that happens in the play and all the events are stagnant. The childish memory shows us the slow and constant rhythm of their everyday life. We see how theyre engaged to simple things like making tea, knitting gloves, picking blackberries or feeding their pets. There is no apparent development of the characters. Romeo and Juliet - Act 3 Scene 1 EssayHowever, having a complete knowledge of the play, the image of these women dancing and catching hands make our sympathy increase for them.. We see them like a chain which will later on disintegrate into small pieces. There are also symbolism that Frier evokes in the play. Michael narrates this one particular moment because it is the final celebration of these women dancing before it changed forever. It was the moment of a new beginning for him as a boy for it was in this summer that he discovered events and felt something for the first time. In his speech, he uses words like, first wireless, August was about to begin, my Uncle Jack, came home from Africa for the first time, I recall my first shock at Jacks appearance, I remember my first delight and for the first time of my life I had a chance to observe him (his father). However, this particular moment represent as well the path leading to their fate the disintegration one be one of the characters. In one part, the play ends with all the characters similar to their position in the beginning of the play. This tableau image signifies how Michael sees his family as he casts back his mind in that summer of 1936. Since for him, it was the beginning and the end, he tries to preserve these freeze characters in his memory. The kite in the play symbolically represents Michael. He is the outsider trapped in a world of women when he was seven. He even distances himself as he narrates this story. However, like a kite, although he is detached from the whole events that occurred, there is still something that attaches him to this particular moment. His memory is comparable to the chord of the kite that connects him to the past. On the other hand, the swaying of this kite reminds us again of the notion of dancing which symbolises the escape for the five women. It is their only way out to release the tensions and pressures imposed by religion and duty. Frier uses Michael to symbolically give a spirit and a life to this plotless play. The lack of plot is supported by the intervals between monologues and dialogues. It is actually through Michaels speech that we feel for the characters. His words are almost representing an explosion of emotions for it is through his speeches that we begin to feel something. It is through him that we discover what happened to Rose and Agnes and that he has a half-brother. However, there is an existing metaphoric symbolism of Michaels role and the other characters representation in the play. The play could symbolise the dance without a melody and Michael, by remembering the past and assessing the whole events through his analytical point of view, gives the rhythm and the harmonious melody to this dance. We observe how the play is almost like a pantomime because the actual text of the play seems to be lacking paralleling the lack of plot. Frier wants to show that words arent really the voice of the truth and that the actions speak louder than words. dancing as if language no longer existed because words were no longer necessary. But we could also view this symbolism in a different way. The whole book is almost like a song that convey several themes. The relationship between the five sisters and the male characters, Jack and Jerry, symbolise seven different notes (do re mi fa sol la ti) that are interrelated to each other creating a melodious harmony. However, to give a spirit to this melody, Michael symbolises the lyrics which gives the life to this song. This is reflected on his liyrical tone. Like the words of a song, he intervenes and overlaps on some of the scene just as how lyrics overlaps on some of the part of a song. And as the characters disappear one by one at the end, the song loses its notes and melodious elements which imply the disintegration of the sisters. Now fade in very softly, just audible, the music It is time to say Goodnight.