Optic Flow Essay Example for Free

Optic Flow Essay The study of optic flow becomes much more complicated when the movement of an observer towards a surface or object is not straight on. In fact, even in the more straightforward condition of straight ahead condition, Gibsons mathematical analysis was wrong. In situations when, for example, we are walking or driving, it is commonly necessary to estimate the chances of collision with an object or surface towards which we are moving obliquely. Similarly, we dont always look straight ahead when moving. The resulting oblique relationships between angle of gaze, direction of movement, and converging paths are much more difficult to analyze. Cutting (1996; Cutting et al. , 1999), has made major contributions to the study of perception during motion by enriching knowledge of the complexities of optic flow. Sensory stimulation is a chemical process which occurs between the human body and brain. When we experience sensation, body is exposed to some type of sensory stimulation. The sensory receptors then receive this information, and transmit it to the brain using neural impulses, or neurotransmitters. There it is interpreted into the correct sensation. Sensations are the basic building blocks of perception. Perception is the process of organizing and making sense of sensory input. Perception allows us to better interpret the information sensory receptors receive, and form images of the world around us. Transduction is what happens when the receptors transform the energies they receive into a form that can be interpreted and utilized by the nervous system. Human beings are able to experience various sensations because the nervous system encodes the messages we are receiving and interpreting. In his doctrine of specific nerve energies, Johannes Muller theorizes that different sensory modes exist because the information received by sensory receptors stimulates different synapses when traveling back to the brain. This is known as anatomical encoding. This type of encoding determines which sensory organ is activated by a certain type of stimulation, according to which specific neural pathway it travels. (Wade, Tavris, 2006). Anatomical Encoding and Sensory Modalities Anatomical encoding does not totally explain how or why different sensory modalities exist independently. Scientists found it difficult to link specific skin senses to individual neural pathways; neither does the doctrine of specific nerve energies explain variations of stimulus within a certain sensory experience, i. . the softness of an animals fur versus the coarseness of sandpaper, or the distinction between the colors light blue and dark blue. A second type of encoding, called functional encoding, is therefore required to make sense of these differentials in sensory perception. According to Wade and Tavris, functional codes rely on the fact that sensory receptors and neurons fire, or are inhibited from firing, only in the presence of specific sorts of stimuli (2006). This means that any given time, some neurons are firing, and some are not. The information regarding the rate of, number of, and patterning of each cells firing is what forms a particular functional code. Sensory adaptation occurs when continual exposure to the same sensory stimulus results in decreased sensitivity to the presented stimulus. Basically this means that given enough time, senses learn to become accustomed to the stimulation receptors gather. The sensory system brings information regarding environment to brains. They help us to interact with environment. The sensory system is made up of five senses, which correspond to five sense organs. The five senses are vision, hearing, taste, touch, and smell. These correspond with the eyes, ears, tongue, skin, and nose. Each of these contains sensory neurons, which transmit impulses to the central nervous system. The information is processed and from that we receive a perception which we interpret and which may change behavior accordingly. This is called Transduction which is the process of the receptors changed the information they receive into a form which the nervous system can utilize. Spatial Projection and The Surface Of The Body Up To The Cortex The visual, auditory, and somatic systemsindeed, all the sensesseem to maintain a spatial projection from the surface of the body up to the cortex. Moreover, connections in each system must be very precise for the signals from the various receptors to be kept straight as they pass up the system. The precision of arrangement is remarkable. (Lappe, M. 2000) It should be in order to ask how such an arrangement came about. What factors are at work as the organism develops to make all the connections come out right? To this question we now have an answer. First, Weiss, then L. S. Stone, and more recently Sperry have gone through a series of ingenious experiments to pin down the factors that control how connections are formed in the nervous system. Sperry, for example, has crossed the sensory and motor nerves in the legs of the rat, and from that has picked up some clues. He has also cut the optic nerve, rotated the eyeballs in various degrees, allowed the nerves to regenerate and then tested animals for the return of spatial vision. There are many details to his experiments, and they prove somewhat confusing, but the upshot of them all is this: Nerve fibers grow back to make the same connections that they made in the first place. To put the matter in another way, the nerve cells along the sensory pathways have some sort of biochemical tags that keep them straight when connections are being laid down. One might say that each nerve cell has a name and that other nerve cells know what that name is. It is still a mystery what these names are and how the cells know each others names and that will be a subject for future research. At any rate, nerves can be badly cut, mangled, and twisted, but somehow or other nerve fibers get back where they belong. For us, it is interesting to know that biochemical factors are at work in laying out the spatial arrangements of the nervous pathways. Lateral dominance has also been a serious problem in getting at the anatomical basis of cognition. That one of hands or feet or eyes is the major one and the other the minor one is a fact not easily disputed. We know, too, that in some affairs one side of the brain is dominant; that is to say, it plays a major role in perception or action, while the other side is minor. Although people have often argued about how important lateral dominance is and how many of the worlds ills it accounts for, few deny altogether that it exists. We must, in fact, believe that some parts of the brain, like the speech area, show very strong one-sidedness and that, in the case of others, the sides share about equally in the functions that concern them. If that be true, how can we tell where to look for a particular function? If one kind of cognition belongs to one side of the brain and we make a lesion in the other side, we will completely miss the point. Or if a type of cognition shares equally corresponding areas on both sides, it takes a perfect bilateral lesion in the areas to make the localization known. We ought to consider, too, the matter of individual differences. We find it natural to say that people are different in the measurements of personality, intelligence, or some other aspect of behavior, but we often seem to assume that brains are standard products turned out on an assembly line so that they look as much alike as new cars. The fact is that brains vary a lot in their size and shape. Lashley has been going into that matter lately, and he assures us that there are individual differences in brain anatomy. It appears that any speculation in this respect is restricted by conditions which are inherent in research experiments. According to observations, only objects or patterns cause any demonstrable satiation. Hence, we must find a process which accompanies object or pattern vision rather than the perception of homogeneous surfaces. The alpha rhythm of the human brain is much more seriously disturbed by visual objects or patterns than it is by a bright homogeneous field. Adrian suggests that it is attention to which the alpha rhythm is so sensitive. But there remains the other possibility that, quite apart from this factor, the rhythm is strongly disturbed by a visual process which accompanies the perception of objects or patterns. Vision Optic Flow and Perception It seems safe to say that, in terms of stimulation, an object is an area (or a volume) which differs from its environment either as a whole or along its boundary. We see things of any kind only when a relation of inequality obtains between the stimulation in one area and that in another, surrounding, and area. Thus it seems plausible to assume that the process which goes with object or pattern vision is a relationally determined process, and that satiation is established in regions in which this process takes place for some time. Relational determination is not a familiar term. Relationally determined processes are extremely common in physics. For instance, if temperatures differ in two parts of a system, a current of heat energy is established which tends to equalize the temperatures. The direction of the flow depends upon the direction of the difference, and in the absence of any difference there is no flow. Merchant, H. , Battaglia-Mayer, A. , Georgopoulos, A. P. 2001) Similarly, if a solution which contains certain molecules is surrounded by a second solution which contains these molecules in a different concentration, a current of diffusion will be observed, unless the solutions are separated by an impermeable barrier. The current flows as long as the concentrations differ. Thus, it is again a relation of inequality between the two parts of the system which maintains the process. Incidentally, examples exhibit relational determination in more than one sense. As the currents of heat or diffusion spread, their distribution in space depends upon the shape of the boundary at which the parts of the systems are in contact. This shape is defined in terms of geometrical relations among parts rather than of merely local conditions, and the distribution of the flow adapts itself to such relations. Therefore, not only the flow as such is relationally determined, but the same holds also for its pattern in space. Some such processes cause obstructions in the medium in which they occur, and that in this fashion after-effects are established when later further processes spread in the same medium. The relationally determined process which underlies pattern vision is a direct electric current and that such a current flow when conditions of excitation in one part of the visual cortex differ from those in an adjacent part. An attempt was also made to explain how the electromotive forces originate which drive the current from one part to the other, and back again to the former. The explanation involved no hypothesis which is at odds with available knowledge of nerve impulses and their influence upon cortical tissue. Vaina, L. M. , Rushton, S. K. 2000) Rather, those forces were derived from concepts which play a great role in present neurophysiological discussions. Nevertheless, this particular part of the theory need not now be described, because there may be various ways of deriving electromotive forces which would drive a direct current through the tissue. It seems that, whatever choice may be, the distribution of the flow as such would always be about the same. It is this flow which we will now consider. The flow would spread through the tissue as a volume conductor, which is to say that, in this connection, the brain must be regarded as a continuous medium to which principles of continuity physics apply. In this respect, there is a possibility which is implicit in present neurophysiology, even though its consequences have, until recently, not been explicitly considered. Surely, if the potentials of the alpha rhythm as well as those of on and off effects can spread through the skull, there is nothing in the brain to prevent such potentials from spreading through this medium as a continuum. As a result, it can hardly be a disturbing thesis that a steadier flow would do the same. (Sherk, H. , Fowler, G. A. 2001) In flowing through a continuum, a direct current assumes a distribution which is relationally determined by the shape of given boundaries. In object or pattern vision, the boundaries in question would be those between cortical areas in which retinal stimulation establishes different kinds or degrees of excitation. It will suffice if we consider a fact which concerns only the distribution of the current as such, and is quite independent of further theorizing. If excitation within a circumscribed cortical area differs from that in its environment, the resulting current must circle around the boundary at which the two areas are in contact. Moreover, unless the surrounded area is very large, the current must be denser in this area than it is in the environment in which it can spread widely. This is true whether or not local excitation is higher in the circumscribed area. Thus, if a black object is shown on a white background, the density of the flow must be maximal within the area of the black object, just as it is maximal within the area of a white object surrounded by black. Satiation and Proximal Energy We can now turn to the problem of satiation. The present theory has no difficulty in solving this problem. Any direct currents which flow through the nervous system polarize the surfaces of cells, and also change their polarizability. Generally speaking, this effect, the so-called electrotonus, has the character of an obstruction. Further currents which afterwards flow through the same medium are weakened. At the same time, they suffer changes of their distribution in space. We are not introducing a special hypothesis if we assume that the currents of theory are also electrotonically active, and that the resulting obstructions follow the same rules as hold for electrotonus in general. For instance, the degree to which the various parts of the medium are electrotonically affected is directly related to the density of the current in those parts. Now we know that the density of the currents postulated in theory must be maximal within the area of a circumscribed object, still great in adjacent parts, and progressively lower at greater distances. Perception is treated throughout as the representation to the individual of real, physical states of affairs of both the external environment and of the self. The former include objects, persons, scenery events, and extended terrain and spaces. States of the self include postures, movements, and activities such as reaching, standing, running, and speaking. Although it is obvious that own physical states are represented to uswe readily and immediately perceive what we are doingthis aspect of perception is usually overlooked in the theoretical treatments, with notable exceptions (Gibson, 1979) Physical states of both the environment and the individual give rise to patterns of energy at the sensory receptors. These patterns, which usually vary over time as well as space, are the proximal stimuli that initiate the chain of neural activity and culminate in a perceptual representation. Certain features of these proximal energy patterns correlate with particular properties or attributes of a physical state of affairs. For example, both the size of the retinal image and the degree of convergence of the eyes correlate with the size of an external object. Likewise, a pattern of stimulation in the joints, tendons, and muscles of an arm correlates with its position. A point to be emphasized is that the features of the proximal stimulus pattern are not simply replicas or necessarily even rough copies of the physical properties that give rise to them. Rather they correlate with them. For example, binocular disparity is in no sense a replica of observer-object distance; it is a correlate of it. This view was first adumbrated clearly by Gibson (1950, 1959) and is emphasized here.

Our Practitioner Article :: Essays Papers

Our Practitioner Article There is always some bandwagon that education seems to jump onto. Unfortunately, sometimes when the majority is in support of the same system, there is a loss of objectivity. They are unable to see both the good and the bad because they are anxious to have developed the "perfect" system. You don’t have to be an educator, but simply a citizen who reads the newspaper or watches the news, to realize that the newest bandwagon is high-stakes testing. In fact those who are parents or have some involvement in a child’s life are most likely seeing the change occurring in the school they are involved with. Some people may argue that testing has always been done. So what is different now? The difference is that now testing (in the form of "high-stakes" testing) is leaving dangerous aftereffects. The end result that may come leaves one even more wary. So, what exactly is high-stakes testing? Is there an exact definition? Personally we believe that one may describe what high-stakes testing is. But, it is more important and more effective to emphasize the unfair strategies high-stakes testing utilizes as well as the disturbing effects it is causing. High-stakes testing is an assessment of students, which carries serious consequences for students or educators. If the student passes, they proceed. If they do not pass, they must repeat the level they are currently at. Why do some people think high-stakes testing is the answer? What are the effects of high-stakes testing? Are there alternatives to high-stakes testing? Fortunately, these are some of the questions we have addressed in this article. High-stakes testing has been implemented in order to "raise the bar for all students and add accountability for academic performance" (Tennessee Department of Education). Many states implement the tests so that they can gather information about student achievement over time. Policy makers have good intentions in that they believe that these tests will improve education. The major goal and hope is that setting high standards of achievement will inspire greater effort on the part of students, teachers, and educational administrators (AERA position statement). As stated previously, many policy makers have good intentions when they implement high-stakes testing. We are not pointing fingers at who is bad and who is good. We are simply pointing out the fact that perhaps the policy makers and society as a whole need to reevaluate what we want from our education system.

Prison Writings: My Life Is My Sun Dance Essay

Leonard Peltier’s Prison Writings: My Life Is My Sun Dance takes into account the disgusting of righteousness in the American justice system and the longings of the Native Americans for evenhandedness, equality and fairplay. Peltier postulate in the story that American socio-cultural life still suffers from the dilemma of racial disparity against many claims that the long tradition of racism in the United States ended with the Civil Rights Movement of the 1960s.This phenomenon still haunts the American society at various levels. But its prevalence in the criminal justice system is more troubling as it harms the cherished ideals off equality, fraternity and freedom of American democracy. So he opines that oppression of American Indians is not unconscious but institutional. The gross foulness in the Justice System is skillfully described in a single line; â€Å"This is the twenty-third year of my imprisonment for a crime I didn’t commit.† On the surface level, it describe the story of killing of two CIA’s agent but on a deeper level Peltier’s has described certain preplanned events that undermine the unalienable human rights clause of the American Constitution. For example he said that Government â€Å"†¦had been gathering in the area for a preplanned paramilitary assault on the Pine Ridge reservation,† (p.129) in 1975. His views are neither a subjective description of personal pathos and miseries, nor it is distortion of the facts but he takes into consideration the national dilemma of treatment of Native Indians and provides verified and verifiable documented proof in favor of his arguments. Another Theme of these personal memoirs is the sun dance that implies the spiritual attainment he had from unbearable agonizing experience in prison. From a warrior to a spiritual leader, the journey is wonderful but is littered with horrible memories of sufferings.

Film Opinion Essay

When I decide to drive to the movie theater or to sit down and enjoy a film, several factors play in my choice of movie. Most of the time, it depends on the mood that I am in. Am I in the mood for something light and funny? Or do I want to submerge myself into a detail-oriented film such as Inception? I take into consideration whether I have enjoyed the actors in previous films, and if I think they will provide the entertainment I am looking for. Has the trailer engaged me long enough to make me interested in the film? Or has the advertising flooded me with information that makes me feel as though the film will be another flop and not worth my time? These are all questions I ask myself when I start to think about watching a movie. Generally, I don’t take movie critic reviews into consideration because I have been disappointed several times in the past, but I will listen to what friends have to say about their experience with the movie. I enjoy most films across all genres. I enjoy when the stories are detailed, and provide a history of the characters, whether through flashbacks or dialogue. I prefer comedies to be humorously dark, sarcastic, or dry. With dramas or action flicks, I prefer for the protagonist to have some tragic faults that lead to their outcome or victory to be sweeter or to justify a better cause than them. I enjoy dialogue-heavy films with actors who can portray the character in a way that makes me believe in them. The recent run of comic-based movies is thoroughly enjoyable to me, due to the rich storytelling and deep backstories from the comic books that the movies accompany. Seeing those characters given life by actors that pull off the mannerisms and attitudes helps ensnare new fans into the world of comics. Science fiction films draw me in because I have always been intrigued by the idea that our technological advancement will eventually cause issues that could lead to humanity’s downfall. When I can watch movies over and over again and find new, interesting subplots or Easter eggs, it makes the experience more rewarding. I do not enjoy films with plotlines that do not make sense, create a story too difficult for the medium to translate properly for the audience, or when movies start plotlines but do not see them through. When watching horror films, slasher films do not pique my interest as much as psychological or religious horror films do. I try to stay away from the general run of the mill action films that come out every summer, that tend to have the same formula as a lot of other action movies. In rare instances, the soundtrack of a film will turn me away if it does not fit the mood and movement of the film. This makes them very predictable and unenjoyable to me. I also find it difficult to watch movies that are based on books but take too many liberties and do not follow the book’s storyline. All in all, I enjoy watching movies and do so several times a week if I have the time. Whether it be new films or favorites that I have watched many times, it is always good to escape from reality for a short time and to relax. Movies have always been a good conversation piece for my circle of friends, and are usually what we choose to do when we get together. I find that I have no problem sitting down and starting any movie at home to see if it will capture my interest, but when it comes to paying for a ticket, I am more picky because I do not want to feel as though I wasted my money.

man versus nature essays

man versus nature essays So God created man in His own image And God saw every thing that He had made, And, behold, it was very good. From the beginning of time, writers and philosophers alike have been setting Man apart from beast, but what is it that makes this partition factual? It is widely believed that Man, by nature, has the capability of consciously contemplating a situation and determining whether the outcome is right or wrong, that Man reacts to a situation by ruling of outlook rather than stimuli, and that Man has more priorities than self-fulfillment; such as religious obligation, parental duties, and cooperative behavior amongst his own kind through social contract. Though these positive characteristics that separate us from our other earthly inhabitants seem superior, these same characteristics may lead us to our own destruction, as well as that of our own planet. Author Mary Shelley discusses the issue of Mans nature through her greatly renowned novel Frankenstein, in which a knowledge crazed scientist is determined to put himself on the scientific map by creating a human-like creature of enormo us strength but with a less than human state of mind. Another author who approaches this idealistic matter is John Locke, who makes clear of this issue in his Political Writings, particularly in Chapter Two: Of the State of Nature. Through the examination of these well-respected minds as well as my personal experience, it is made clear that certain unique characteristics separate Man from animal. As one observes a pet, it is obvious that there are tremendous differences between the observer and the animal. My seven-year-old obese beagle, Muggsy, has no value of right and wrong. He holds no respect towards those who supply him with the necessities of living or the requirements of comfort. For example, Muggsy tends to steal objects around the house and refuses to giveback the item. He...

Using the Spanish Verb Haber

Using the Spanish Verb Haber Haber is one of the most common verbs in Spanish, used most of the time as an auxiliary or helping verb. Although haber is similar in form to have and is often translated that way, it is unrelated to the English verb. Haber has three main uses as seen below. Haber as an Auxiliary Verb in Compound Tenses When used as an auxiliary verb, haber is the equivalent of the English auxiliary to have (which is much different than the English to have when it means to possess). Haber is used to form what is known as the perfect tenses because they refer to actions that have been or will be completed. (Completed used to be a common meaning of perfect.) As in English, the perfect tenses are formed by following a form of haber with a past participle. He comprado un coche. (I have bought a car.) ¿Has estudiado? (Have you studied?)Han salido. (They have left.)Habr salido. (She will have left.)Habrà ­a hablado. (I would have spoken.) In English, it is very common to insert an adverb or another word between the two parts of a compound verb, such as in the sentence he has always gone. But in Spanish (except perhaps in poetry), the two verb parts arent separated. As a beginner, you dont need to learn all the tenses using haber now, but you should be able to recognize haber when it is used. You should also be aware that while the perfect tenses in Spanish and English are quite similar in form, they arent always used in exactly the same way. Haber for There Is or There Are One peculiarity of haber is that it has a unique conjugated form, hay (pronounced basically the same as the English eye) that means there is or there are. Hay una silla en la cocina. (There is one chair in the kitchen.)Hay dos sillas en la cocina. (There are two chairs in the kitchen.) Note that in the above examples, the English there isnt referring to location, but to mere existence. The most common word for there in terms of location is allà ­. Example: Hay una silla allà ­. There is a chair there. Haber can be used in this way in tenses other than the present, although not as commonly. In formal Spanish, as in the second example above, the singular form of the verb is used even when it refers to more than one person or thing. Haber  in Idioms Haber can be used in a number of idioms, which are phrases that have a meaning apart from the meanings of the words in them. The one youll run into most often as a beginner is haber que, which means to be necessary when followed by an infinitive. When used this way in the present tense, the hay form of haber is used. Hay que saltar. (It is necessary to jump.)Hay que conocerlo para comprenderlo. (It is necessary to know him in order to understand him.)Habr que salir a las dos. (It will be necessary to leave at 2 oclock.) Conjugating Haber As is the case with most other common verbs, haber is conjugated irregularly. Here is the conjugation for its present indicative tense, the one used most often. yo (I) he I have tà º (informal singular you) has you have usted (formal singular you), à ©l (he), ella (she) ha (sometimes hay) you have, he has, she has nosotros, nosotras (we) hemos we have vosotros, vosotras (informal plural you) habà ©is you have ustedes (formal plural you), ellos, ellas (they) han (sometimes hay) you have, they have

NUTRITION RELATED DISEASE Assignment Example | Topics and Well Written Essays - 1750 words

NUTRITION RELATED DISEASE - Assignment Example If proper precautions are not taken during processing then there are chances that they may contaminated. Keeping food in open for over 2 hours at room temperature may cause bacterial growth in food and consuming such food may cause illness (Medicine Plus, 2014). Certain kinds of illnesses cause due to lack of nutrients in food. For example, vitamin D deficiency causes cardiovascular disease, asthma, cancer, or rickets. Iron deficiency many lead to anemia in the body. Lack of vitamin C affects immune system and lead to decreased metabolism. Vitamin A is necessary for maintaining good vision and prevents several eye related ailments. Vitamin D is essential for keeping bones and teeth strong preventing its decay (MedicineNet.com, 2014). Safe food is extremely critical to keep body free of diseases. Food gets contaminated through several means that include improper storage, inadequate cooking temperatures, cross-contamination from animal waste, improper or insufficient hand washing. Microbes get transferred from utensils, common knife and cutleries when not washed properly in between uses. Meat and poultry gets contaminated during slaughter; even fruits and vegetables get contaminated by infected water during wash. Insufficient cooking may not eliminate pathogens completely if already present (Minnesota Department of Health, 2013). Water, soil, plants are the sources of this pathogen. They are also present in intestinal tracts of fish and animals. They do not require oxygen to survive. Canned foods including vacuum-packaged may contain these bacteria. Incubation time for this pathogen has been found between 12 and 72 hours. Usual symptoms are diarrhea, vomiting, muscle weakness, blurred vision and difficulty in swallowing. Presence of these pathogens in food may cause diarrhea and abdominal cramps. Usually, poultry, meats, dried and precooked foods are the sources. Incubation time is