Thi thử VSTEP – 10 Bài Reading Test 5 Part 2

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 3
Questions 21-30

Today we know that the mind is a product of the brain, but how exactly does this 1.5-kilo (three-pound)piece of fleshcreate a mind that allows you to think about yourself, experience happiness and anger, or remember events that happened 20 minutes or 20 years ago? This isn’t a new question. Today, however, powerful new techniques for visualizing the sources of thought, emotion, behavior, and memory are transforming the way we understand the brain and the mind it creates.

Have you ever stopped and thought, “What’s wrong with me today? I just don’t feel like myself”? This self-awareness – the ability to think about yourself and how you’re feeling – is an important part of being human. This part of your mind has its origins in the prefrontal cortex – a region of your brain just behind your forehead that extends to about your ears. Before this area began to function (around age two), you didn’t understand that you were a separate entity with your own identity. In time, as this part of your brain developed, you became more aware of yourself and your thoughts and feelings.

Perhaps one of the most important factors involved in shaping our identity is memory. Most scientists define it as a stored pattern of connections between neurons in the brain. Every feeling you remember, every thought you think, alters the connections within the vast network of brain cells, and memories are reinforced, weakened, or newly formed. Most people’s earliest memories reach back to about age three or so. Very few people recall anything before this time because the part of the brain that helps form long-term memories (the hippocampus) was not yet mature, or fully developed. This doesn’t mean earlier memories don’t exist in your mind, though. Some scientists believe highly emotional memories might be stored in another structure in the brain (the amygdala) that may be functional at birth. Though these memories are not accessible to the conscious mind, they might still influence the way we feel and behave, even into adulthood.

But where do our emotions come from, and how do they shape the people we are and the way we perceive the world? Forty years ago, psychologist Paul Ekman demonstrated that facial expressions used to exhibit certain emotions are recognized by people everywhere. Ekman suggested that these emotions and theircorrespondingfacial expressions evolved to help us deal quickly with situations that can affect our welfare. Though humans may share certain emotions and recognize them in others, we don’t all have the same emotional response to every situation. In fact, most emotional responses are learned and stored in our memories. The smell of freshly cut grass, for example, will generate happy feelings in someone who spent enjoyable childhood summers in the countryside, but not in someone who was forced to work long hours on a farm. Once an emotional association like this is made, it is very difficult to reverse it. But we can learn to control our emotions by becoming consciously aware of their underlying causes and by not reacting automatically to things in our environment.

But is it really possible to control our emotions? Researcher Richard Davidson has demonstrated that people who experience negative emotions display activity in the right prefrontal cortex. In those with a more positive perspective, the activity occurs in the left prefrontal cortex. He conducted a study on whether or not people can shift their negative feelings toward a calmer state of mind. In his research, one group of volunteers received eight weeks of training using meditation and relaxation techniques and at the end of the study, they showed a clear shift in brain activity toward the left happier frontal cortex.

For centuries, people have studied the brain, but it is only in recent years that we have really started to learn how it works. Nevertheless, there is still a long way to go before we understand our mind’s many complexities.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.

PASSAGE 4
Questions 31-40

In recent years, the oceans have been seen as a potential source of renewable energy. Some estimates say that during the second decade of this century, ocean energy sources will generate more than 1,000 megawatts of electricity, which is enough to power a million homes in the industrialized world. Several technologies have been developed for exploiting these resources in a practical way, among which ocean thermal energy conversion (OTEC) is one of the most promising. Experimental OTEC plants have been constructed using different operating principles, although as yet no large-scale commerciallyviableplant has been launched.

The basic operation behind this system uses the heat energy stored in the oceans as a source of power. The plant exploits the difference in water temperature between the warm surface waters heated by the sun and the colder waters found at ocean depths. A minimum temperature difference of 20 degrees Celsius between surface and depth is required for efficient operation, and this situation is typically found only in tropical and subtropical regions of the world. There are two basic kinds of OTEC system: the open cycle system and the closed cycle system. In the open cycle system, the warm surface water is converted into steam in a partial vacuum and this steam drives a turbine connected to an electrical generator. In a closed cycle system, the warm surface water is used to boil a fluid, such as ammonia, which has a low boiling point. In both systems cold water pumped up from the ocean depths condenses the vapor. In the open system, the steam is condensed back into a liquid by cold water pumped from deep-ocean water and then discharged. In the closed system, the condensed ammonia is used to repeat the cycle continuously.

The OTEC system is potentially an important source of clean, renewable energy, which could significantly reduce our reliance on fossil fuels and nuclear fission. [A] Unlikeother formsof renewable energy, such as those provided directly by the sun and wind, OTEC plants can generate power all the time. Furthermore, the design of this technology avoids any significant release of carbon dioxide into the atmosphere. [B] Aquaculture is one important spinoff. [C] It may also be economically feasible to extract minerals from the pumped seawater. [D] Freshwater for drinking and irrigation is another by-product, and this will be an important advantage in regions where freshwater is limited.

Some drawbacks to this form of power generation have been noted. Perhaps the biggest drawback at present is the high capital cost of initial construction due mainly to the expense of the large pipeline used to pump water from 1,000 meters below the surface. Furthermore, the conversion of thermal to electrical energy in the OTEC system works at very low efficiency as the output power needed to pump a lot of water for production. There are also potential ecological drawbacks, since the water discharges will change the water temperature and disturb some marine habitats.

The main obstacle created by high initial expenses will have to be met before OTEC competes withconventionalalternatives, and until such time, OTEC will remain restricted to experimental plants. When technology permits lower start-up costs, this technology will make an important contribution to world energy requirements.