Laurie Burns Studying Triple-GEM foils

Laurie Burns Studying Triple-GEM foils In 1997, Fabio Sauli invented the Gas Electron Multiplier (GEM) at CERN, the worlds largest particle accelerator. A triple-GEM consists of thin layer of insulating material called Kapton sandwiched between two sheets of copper, making a grand total of three layers (the triple comes from the three separate GEM foils that are stacked to make the final detector.) The composite sheet is then patterned with an array of 600,000 tiny holes (about 70 um in diameter) using a chemical etching process The sheet can be used to detect particles by amplifying ionization patterns by up to ten times. Researchers at the Plasma Science and Fusion Center in the Laboratory for Nuclear Science (LNS) at MIT have developed a prototype detector. Under the guidance of Professor Bernd Surrow and a postdoc, senior Laurie Burns is testing and comparing two types of GEM foils that may be used in future models. GEMs are able to detect particles using well-known physical principles. When a voltage is applied to the foils, a voltage difference appears because the Kapton is an insulator and does not let current pass. This voltage difference creates an electric field, so if a few electrons were to come near the foil, the charge on the surface would be amplified below. It may be easier to think of the GEM as a sort of microscope for charges, where each foil acts as a lens. Once the microscope is hooked up to all the appropriate auxiliary equipment such as an oscilloscope, it can detect, for example, whether a particle is an electron or a positron based on which direction the particle turns in a magnetic field. Most GEMs currently use foils that were created by the CERN Surface Treatment Service. Since CERN is a research facility and not a foil producing business, MITs BatesCenter has begun fabricating its own foils. This is a very delicate process, as a piece of copper stuck in only one of the 600,000 holes can cause the foil to fail. Laurie began her UROP last spring and continued through the summer, where she mostly worked on using scanning software to examine the foils from CERN and Bates. As part of her senior thesis project, she will eventually conduct a comparative study between the two foils by making two model detectors to assess each foils properties such as its gain and lifetime. Once the findings of her study are complete, the LNS hopes to develop a triple-GEM that has a surface area nine times larger than the detector currently in use. Lauries research on triple-GEMs has a lot of fascinating applications. The application that I found most impressive was the ability to detect cosmic rays muons. In general, the GEM is better than other detectors because it is safer to use and produces more gain (ratio of signal output to input). As a physics (course 8) major, Laurie emphasizes that most physics students have the opportunity to conduct experiments in their junior year in the junior lab class. Through the class, students perform eight experiments that provide exposure to various aspects of experimental physics. She says that, in general, physics majors get their first UROPs in their junior year because a lot of background knowledge is necessary to complete meaningful research. Laurie also discussed some research being done by her fellow physics majors. They include studying: Lasers to figure stuff out about gravity (LIGO) Computer processes involving physics at the Lincoln Labs Computer simulations in a joint project with the Stanford Linear Accelerator Center A two-dimensional harmonic oscillator and finding the solutions to it Quantum physics String theory Time travel charge parody (to find out more about this, take Special Relativity (8.20) to find out how to travel into the future!) Astrophysics Lasers (pulsing, optical physics) Originally from Massachusetts, Laurie says that her high school physics teacher is one the reasons she decided to be course 8. In her free time, she likes to play the violin and in the past she was in the MIT Chamber Orchestra. She also likes playing intramural sports like ice hockey and is very involved with her sorority. Laurie is currently in the process of applying to graduate schools in applied physics departments and hopes to research optics in the future. She also has a minor in French and is thinking about putting some of her language skills to use while conducting research at CERN.

Hurtful Love and Foolish Hope in Death of a Salesman Essay

nbsp;Hurtful Love and Foolish Hope in Death of a Salesmannbsp;nbsp;nbsp;nbsp;nbsp; A father is an important role model in a young mans life; perhaps the most important. A father must guide his children, support them, teach them, and most importantly, love them. In the play Death of a Salesman, written by Arthur Miller, an aging salesman of 63, Willy Loman worked all his life for his children. Happy and especially Biff, his two sons, where his pride and joy and his reason for living. Willy tried as hard as he possibly could to provide for them, to support them, to mold them into men; but he failed. Willys greatest fault, perhaps, was his inability to see his sons for what they really were. Biff and Happy were never destined to†¦show more content†¦If only Willy would have recognized his son Biffs mediocrity instead of believing he was a great kid, Biff may have become a good man. No matter what Biff did, Willy would never believe it was because he was incapable of success. Unlike his older brother Biff, Happy did not receive the affection or attention he craved from his father. Willys preoccupation with his more attractive, better-liked son Biff, left Happy trailing in his siblings footsteps. Happy always tried to get his parents attention, hoping one day he could please them. Im losing weight, you notice, Pop? (29). Im gonna get married, Mom. I wanted to tell you. (68) Yet Willy never noticed his younger sons accomplishments. The lack of recognition from his father only made Happy try harder, but he could only do so much. Happy, not unlike his older brother Biff, was not a great man. In hopes to please his father, Happy also went into the selling business, but met little success. He was one of the two assistants to the assistant buyer and was miserable. Biff questioned Happy, Are you content, Hap? Youre a success, aret you? Are you content? (23), and Happy responds, Hell, no! Yet Happy stuck with his job, longing to one day please his father. Even aft er Willys death Happy did not give up on his quest. Im gonna show everybody else that Willy Loman did not die in vain. Im staying right in this city, and Im gonna beat this racket! (138). Happy, still trying

What Does The Deaf Education Curriculum Does Not Build A...

Auditory challenged individuals are comprised of nearly 10,000,000 hard-of-hearing and 1,000,000 functionally deaf Americans and a half a million were born or diagnosed deaf before turning eighteen years old in the United States (Mitchell 2006). A great percentage of this demographic primary language is American Sign Language (ASL). These individuals are considered a verbal minority. Within the deaf community â€Å"deaf† is defined as people who have been deaf or hard of hearing entirely or most of their lives. In addition to sign language, auditory challenged individuals use broken speech usually no higher than a fourth grade level (Hauser, O’Hearn, McKee, Steider, Thew 2010). The basic deaf education curriculum does not build a solid†¦show more content†¦Although, at times, I felt anxious because I could not hear my kids playing. I kept checking on them. I look at my husband if I felt the floor slightly rumble because I can see the dogs barking and running t oward our front door which usually meant someone walked by the house. When my kids had a question it was recited to my husband. H wrote it down than I verbally answered. It got confusing because my husband stated he started talking and realized half way I did not hear anything. It was different without using my ears because we did not go into details about our day. He nor I felt like writing a two page report about our day. We summed up the important stuff in a few sentences. My husband had to signal me when the microwave dinged. I do not think that there was anything I notice without having my hearing that I would have not notice otherwise. Vacuum was a bit difficult because I could not hear if it accidentally turned off. Normally we I use it as a hearing person I have a tendency to cut it off by mistake due to the location of the bottom. So when I could not hear. I tried to pay more attention to the vibrations on the floor. I feel bad for persons who are auditorally challenged. They are the minority in a linguistic world. Mostly everything is gears to an able body who has complete range of all their senses. I don’t think my attitude has change I have always been aware how difficult it is being disable if not deaf, blind. I

The Secret Guardian of Gotham Free Essays

The Dark Knight portrays Batman well enough for the audience to easily analyze Batman’s characteristics and personality. Batman is one of the most crucial characters in the movie. Bruce Wayne, or Batman, is portrayed as a billionaire and an owner of a gigantic industry, who actually at night works as a vigilante fighting criminals with his bare hands. We will write a custom essay sample on The Secret Guardian of Gotham or any similar topic only for you Order Now Batman’s sense of morality, self-righteousness, and self-sacrificial attitude in his actions allow effortless classification of Batman’s characteristics in True Color’s Personality Test, Myers-Briggs Personality Test, and Maslow’s Hierarchy of Needs. The way Batman believes the good in people, and the way he spends his nights for the safety of the people in Gotham proves that Batman is most likely the color blue from the True Colors Personality Test. People with blue characteristic hate with fervor, value harmony, give self to others, promotes feelings and warmth among people, and are too generous. Batman falls into all of these descriptions. Even though Batman abhors Joker, he never kills Joker despite all of the chances he is given because he believes in change in human potential, because he wants to inspire others through his actions, and because of his stern self righteousness of always wanting to do what is good for everyone. Also when Harvey Dent died after killing five people â€Å"fairly,† Batman tells Lieutenant Gordon to point the finger at him instead of Harvey Dent. Batman says, â€Å"You will hunt me. You will condemn me. Set the dogs on me, because that is what needs to happen,† (The Dark Knight) in order for people of Gotham to not lose hope by hearing and seeing the downfall of the Gotham’s White Knight, Harvey Dent. This sacrificing attitude is difficult to find in the characteristics of orange, green, and gold, but is the compassionate feature of the color blue. Towards the end of the movie, when Joker sees that the two ships didn’t bomb each other, Batman tells him, â€Å"This city just showed you that it is full of people ready to believe in good,† (The Dark Knight) implying that he, as well, believes in good nature of humans. From what is shown, my hypothesis would be that Bruce Wayne’s dichotomies are ESFJ, or extraverted, sensing, feeling, and judging. Even though Bruce Wayne is surreptitiously living another life as Batman, with only a few close confidants being aware of it, he seems to enjoy social gatherings and occasional dates with many different women. He approaches his criminals through high tech researches and careful observations of facts and proofs. Batman also does not use his sudden insights to act and rather weighs the different possibilities using his tangible sources. Therefore, I assume that Batman is more sensing than intuitive. Bruce Wayne is more feeling in the way he processes data because he considers the points of view of other people and he tries to do whatever establishes harmony within the society. For example, when Bruce Wayne had turned every cell phone in the city into a microphone and a high-frequency generator receiver, knowing that Lucius would not like such dangerous machine, he made it accessible and destructible by only Lucius. Also knowing that citizens of Gotham will lose hope and faith if they learn the truth behind Harvey Dent’s fall and death, Batman says, â€Å"Sometimes the truth is not good enough. Sometimes people deserve more. Sometimes people deserve to have their faith rewarded. † (The Dark Knight) Batman also shows his willingness to do whatever is needed to help Gotham by saying, â€Å"I am whatever Gotham needs me to be. † (The Dark Knight) Maybe because Batman is so engrossed in many different endless jobs he has to finish, he never seems to be having his pleasure and leisure time. He always seems to be task oriented and organized in his plans and well in control with the help of Alfred Pennyworth and Lucius Fox so that the plans never fail. Watching this movie, I could not help but notice the parallel between Jesus from the Bible and Batman. Just like the historical character Jesus, who supposedly had no sin and dedicated to give up his own life for the forgiveness of others, and who eventually gets accused by the same people who used to acclaim him as the â€Å"Savior,† Batman, who did nothing against the morals, gets chased by those who used to praise him as the â€Å"Hero,† by becoming the scapegoat. Therefore, in Maslow’s Hierarchy of Needs, even though I believe that Batman is sometimes on the level of safe and security because he gets injured often while fighting against criminals and Joker, Batman is primarily on the level of self-actualization. He truly dedicates himself for the benefit of others and to satisfy what the citizens of Gotham want. He knows what he is meant to do and does what he does not as a service for himself but as a guidance for the citizens of Gotham. Lieutenant Gordon, watching Batman run away, tells his son, â€Å"Because he is the hero Gotham deserves, but not the one it needs right now, so we will hunt him because he can take it. He is not our hero; he’s a silent guardian, a watchful protector, a dark knight. † (The Dark Knight) Bruce Wayne, Batman, or the Dark Knight’s characteristics summed together support Batman’s famous quote, â€Å"Batman has no limits. † (The Dark Knight) The way he dives into danger every day, cleans up all the violent and illegal mess made in Gotham, and sacrifices himself for people’s mental comfort proves his idealistic characteristics. Because he has no limit, I believe he was able to be the person and the hero portrayed in the movie. Without Batman, his perfect sense of morality, and his boldly courageous deeds, Gotham would not be the same. How to cite The Secret Guardian of Gotham, Essay examples

Developmental Defects of Teeth Essay Example

Developmental Defects of Teeth Paper developmental defects of teeth with recent genetic concepts INTRODUCTION: Disorders of development of teeth may be prenatal or postnatal in origin and may be inherited or acquired. Their recognition and evaluation requires a thorough knowledge and evaluation of the normal chronology of the human dentition and of the normal development and structure of the teeth. Disorders of development of teeth of teeth may be due to abnormalities in the differentiation of the dental lamina and the tooth germs, causing anomalies in the number, size and form of teeth (abnormalities of morphodifferentiation) or to abnormalities in the formation of the dental hard tissues resulting in disturbances in tooth structure (abnormalities of histodifferentiation). Abnormalities of histodifferentiation occur at a later stage in development than abnormalities of morphodifferentiation; in some disorders both stages are abnormal. Histophysiology of tooth development: A number of physiologic growth processes participate in the progressive development of the teeth. These are – 1. Initiation The dental lamina and associated tooth buds represent those parts of the oral epithelium that have the potential for tooth development. Different teeth are initiated at different times. Initiation induction requires ectomesenchymal epithelial interaction. A lack of initiation results in the absence of either a single or multiple teeth or complete lack of teeth. Abnormal initiation may result in the development of single or multiple supernumerary teeth. 2. Proliferation We will write a custom essay sample on Developmental Defects of Teeth specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Developmental Defects of Teeth specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Developmental Defects of Teeth specifically for you FOR ONLY $16.38 $13.9/page Hire Writer Enhanced proliferative activity after initiation results successively in the bud, cap and bell stages of the odontogenic organ. Proliferative growth causes regular changes in the size and proportions of the growing tooth germ. A disturbance has entirely different effects according to the time of occurrence and the stage of development that it affects. Tooth anomalies may include disturbances in the size, proportion or number of teeth 3. Histodifferentiation It succeeds the proliferative stage. The formative cells of the tooth germ developing during the proliferative stage undergo definite morphologic as well as functional assignment. Differentiation of odontoblasts and ameloblasts takes place resulting the formation and apposition of enamel and dentin. Disturbance is the stage results in defects in the structure of tooth like amelogensis imperfecta type 1 and 4. 4. Morphodifferentiation The morphologic pattern or basic form and relative size of the future tooth are established by morphodifferentiation that is by differential growth. Dentinoenamel junction and dentinocemental junctions are established. Disturbances in morphodifferentiation may affect the form and size of the tooth without impairing the function of the ameloblasts or odontoblasts. 5. Appposition It is the deposition of the matrix of the hard dental structures. Defects in apposition results in anomalies like amelogenesis imperfecta type 2, dentin dysplasia. 6. Mineralization and Maturation After matrix formation full mineralization and dental hard tissue maturation. Anomalies like amelogensis imperfecta type 3, fluorosis and interglobular dentin. CLASSIFICATION OF DEVELOPMENTAL DEFECTS OF TEETH 1. Anomalies of initiation and proliferation anomalies of number hypodontia and anodontia hyperdontia anomalies of size Microdontia Macrodontia anomalies of shape Germination Fusion Concrescence 2. Anomalies of morphodifferentiation anomalies of size and shape Dilacerations Dens invaginatus Dens evaginatus Taurodontism Talon cusp 3. Anomalies of histodifferentiation enamel defect Amelogensis imperfecta type I dentin defect Dentinogensis impefecta type I,II,III 4. Anomalies of apposition enamel defects Amelogensis imperfecta type II, IV Enamel hypoplasia Enamel pearl dentin defec ts Dentin dysplasia Regional odontodysplasia cementum defects Hypercementosis Hypophophatasia 5. Anomalies of mineralization enamel defects Amelogenesis imperfecta type III Enamel fluorosis Anomalies of initiation and proliferation Development disturbances in number a. ypodontia and anodontia True anodontia or congential absence of teeth may be of two types Total anodontia – in which all teeth are missing. It may involve both deciduous and permanent teeth. It is a rare condition when it occurs it is frequently associated with generalized disturbances, hereditary ectodermal dysplasia. Partial anodontia (hypodontia or oligodontia) Hypodontia when there is lack of development of one or more teeth Oligodontia is a subdivision of hypodontia indicating the lack of development of six or more teeth. An incidence of 1. 5 – 10% is seen excluding 3rd molars in permanent dentition and . 09 . % for primary dentition. Most frequently affected teeth are 3rd molars, mandibular 2nd premolar, maxillary lateral incisor and maxillary 2nd premolar. In case of deciduous dentition usually maxillary lateral incisor are missing. According to Grahen and Granath there is a close correlation between congenitally missing deciduous teeth and their permanent successors suggesting a genetic factor. A familial tendency for this defect is noted. Graber reported enough evidence that it is actually the result of one or more point mutations most often transmitted in an autosomal dominant pattern with incomplete penetrance and variable expressivity. Some investigators implied that hypodontia is a normal variant suggesting that humans are in an intermediate stage of dentitional evolution. A proposed future dentition would include one incisor, one canine, one premolar and two molars per quadrant. Hypodontia correlates with the absence of appropriate dental lamina. Mostly this is due to genetic alteration. However, environmental factors like trauma, infection, radiation and endocrine disturbance may also result in loss of developing tooth bud. Hypodontia is associated positively with microdontia, reduced alveolar development, increase free way space and retained primary teeth. Pax 9 gene maps to chromosome 14, it encodes a transcription function that is important in the development of pharyngeal pouches. Its mutation may lead to congenitally missing teeth. Syndromes associated with hypodontia: cleft lip/palate crouzon syndrome down syndrome hyphidrotic ectodermal dysplasia ellis van crevald syndrome oro facial digital syndrome b. hyperdontia it is the development of an increase number of teeth. Genetics of hyperdontia suggests an autosomal dominant pattern of inheritance with incomplete penetrance. The variable expression and penetrance of the gene may be affected by the environmental factors. The development of hyperdontia is development of excess dental lamina which leads to formation of additional teeth. An incidence of . 3-3% and a male to female ratio of 2:1 is noted. It occurs most frequently in permanent dentition and approximately 90% of cases present in maxilla with a strong predilection for the anterior region. Terms used to describe supernumerary tooth depending on their location i. Mesiodens is located in the maxillary incisor resion. It is the most common supernumerary. ii. Distodens/ distomloar is the accessory fourth molar iii. Paramolar is a posterior supernumerary tooth situated lingually or buccally to a molar tooth. Classification based on morphology In the primary dentition morphology is usually normal or conical. Greater variety is seen in case of permanent dentition Conical is a small peg shaped conical tooth and is the most common supernumerary. It develops with root formation ahead or at an equivalent stage to that of permanent incisor. It can result in rotation or displacement of the permanent incisor but rarely delays eruption. Tuberculate possess more than one cusp or tubercle and is barrel shaped. Root formation is delayed as compared to permanent incisors. They are often paired and are commonly located on the palatal aspect of the central incisors. It results in delayed eruption of the incisors. Supplemental refers to a duplication of teeth on the normal series and is usually found at the end of the tooth series. Most commonly permanent maxillary lateral incisor is the supplemental supernumerary. Majority of the deciduous supernumeraries are of this type. Odontome is listed as the fourth category by Howard. It is a hamartomoatous malformation nd is composed of more than one type of tissue called composite odontoma. Mainly two types are there complex and compound. Syndromes associated with hyperdontia 1. cleft lip/palate 2. cleidocranial dysplasia 3. gardner syndrome 4. oro facial digital syndrome Developmental disturbances in size of tooth a. microdontia – teeth which are smaller than normal. Females demonstrates a higher a frequency of microdontia and hypodontia. Thre e types are True generalized microdontia in this all the teeth are smaller than normal. It is seen in cases of piutatry dwarfism, Down syndrome, congenital heart diseases. Relative generalized microdontia normal slightly smaller teeth present in the jaws larger than normal producing an illusion of microdontia. Role of hereditary as jaws are inherited from one aren’t and tooth size from other parent. Microdontia involving single tooth is common condition affects maxillary lateral incisors and 3rd molar most commonly. b. macrodontia – teeth that are larger than normal. Three types similar to that microdontia True generalized macrodontia all teeth are large. Seen in cases of pituitary gigantism and pineal hyperplasia with hyperinulinism. Relative generalized macrodontia presence of normal teeth in similar jaw giving an illusion of macrodontia Macrodontia of single tooth relatively uncommon. Occasionally seen in cases of hemihypertrophy of the face. Should not be confu sed with fusion of teeth. Development disturbances of shape of teeth a. germination – anomalies which arise from an attempt at division of single tooth germ by an invagination with resultant incomplete or complete formation of teeth. Incidence of . 5% is seen and it more common in primary dentition. Higher frequency in maxillary anterior region. It may retard eruption of permanent successor. Usually appear as one with two completely or incompletely separated crowns that have a single root and root canals. Twining production of equivalent structure by divisions resulting in one normal and one supernumerary tooth. Etiology is unknown although a genetic basis has been suggested. b. fusion – union of two normally separated tooth germs. Depending upon the stage of development of the teeth at the time of the union. More common in the deciduous than in the permanent dentition. Union by dentin, separate pulp chambers/ canals. May retard eruption of permanent successor. . concrescence – form of fusion which occurs after root formation. Teeth are united by cementum only. As a result of traumatic injury or crownding of teeth with resorption of the interdental bone. More frequently in the posterior and maxillary region. Anomalies of morphodiferentiation Anomalies of size and shape a. dilaceration: An angulation or a sharp bend or curve in the root or crown of a formed tooth. Due to trauma during the period in which the tooth is forming, with the result that the position of the calcified portion of the tooth is changed and the remainder of the tooth is formed at an angle. Syndrome associated with dilaceration. Lamellar ichthyosis. Present difficulty at the time of extraction. b. dens invaginatus: dens in dente It is a deep surface invagination of the crown or root that is lined enamel. Results due to invagination in the surface of tooth crown before calcification has occurred. This can be due to increased localized external pressure focal growth retardation and focal growth stimulation in certain areas of the tooth buds. The permanent maxillary lateral incisors are the teeth most frequently involved. Two forms are usually seen as Coronal dens in dente – more frequent prevalence varies from . 4% to 10%. Depth of iinvagination varies from a slight enlargement of the cingulum pit to deep infolding that extends to the apex. Radicular dens in dente – rare and thought to arise secondary to proliferation of hertwig’s root sheath with the formation of a strip of enamel that extends along the surface of the root. Radiographiclaly the affec ted tooth demonstrates an enlargement of the tooth. It chances of caries and pulp infection. c. dens evaginatus – Leong’s premolar it is a developmental condition that appears clinically as an accessory cusp or a globule of enamel on the occlusal surface between the buccal and lingual cusps. Unilaterally or bilaterally with an increased mandibular predominance. Pathogenesis is the proliferation and evagination of an area of the inner enamel epithelium and subjacent odontogenic mesenchyme in to the dental organ during early tooth development. If seen in association with another varaiton of coronal anatomy. Shovel shaped incisors affected incisors demonstrate prominent lateral margins, creating a hollowed lingual surface. Maxillary incisor is the most commonly affected. This extra cusp may contribute to incomplete eruption, displacement of teeth and/or pulp exposure with subsequent infection following occlusal wear or fracture. . taurodontism – it is an enlargement of the body and pulp chamber of multirooted tooth with apical displacement of the pulpal floor and bifurcation of the roots. Overall shape of the taurodont resembles that of the molar teeth of cud chewing animals â€Å"bull like† Shaw classified taurodont teeth into 3 division according to the degr ee of apical displacement of pulpal floor hypotaurodont (mild) mesotaurodont (moderate) hypertaurodont (severe) may occur as an isolated trait or as a component of specific conditions like 1. klinfilter’s syndrome . amelogenesis imperfecta 3. orofacial digital syndrome 4. hypohydrotic ectodermal dysplasia 5. tricho dento osseous syndrome 6. down syndrome It is seen that taurodontism may develop in presence of any one of a large number of different genetic alterations. These findings suggest that chromosomal abnormalities may disrupt the development of the tooth form and that taurodontism is not the result of any specific genetic abnormality e. talon’s cusp – Is also known as dens evginatus of the anterior teeth. It is a well delineated cusp that is located on the surface of an anterior tooth. Predominantly affects permanent dentition esp maxillary lateral incisors. It projects from the lingual surface of the affected tooth and forms a three pronged pattern that resembles an eagle’s talon. The cusp blends smoothly with the tooth except that there is a deep development groove where the cusp blends with the sloping lingual tooth surface. It is associated with other dental abnormalities like supernumearary teeth, odontomas, impacted teeth; peg shaped lateral incisors and dens invaginatus. It is also associated with other syndromes like Rubinstein Tyabi syndrome Sturge Weber syndrome. Complications like interference with occlusion, comprised esthetics, displacement of teeth, caries, periodontal problems and irritation of the adjacent soft tissue may occur. ANOMALIES OF HISTODIFFERENTIATION Enamel defects a. Amelogenesis imperfecta type I AI is a heritable enamel defect in the absence of any systemic disease. Reported incidence varies from 1:14000 to 1:4000. Multiple inheritance patterns are noted. It may differentiated into 4 main groups depending on the clinical presentation and the likely stage of enamel formation that is primarily affectes. hypoplatic hypocalcified hypomature hypomature hypoplastic with taurodontism Each group is further subdivided into several subgroups depending on the mode of inheritance as well as the clinical appearance of the defective enamel. Genetic studies – have shown that etiology of AI is related to the alteration of genes involved in the process of formation and maturation of the enamel. X linked AI has shown the defectiv e gene is closely linked to the locus DXS85 at Xp22. this site has been identified as the general location of the human gene amelogenin the principal protein in the developing enamel. In the case of autosomal dominant type of AI the locus of the defective gene is on the ch 4q21 to which enamel protein enamelin maps. AI type I Hypoplatic The basic alteration centers an inadequate deposition of enamel matrix. Any matrix present is mineralized appropriately. Subgroups (Witkop 1989) I A – hypoplastic, pitted AD I B – hypoplastic, local AD I C – hypoplastic, local AR I D – hypoplastic, smooth AD I E – hypoplastic, smooth XR I F – hypoplastic, rough Ad I G – enamel agenesis, AR Clinical feature: In the generalized pattern pinpoint to pinhead sized pits are scattered across the surface of the teeth. Buccal surfaces of the teeth are affected and staining of these pits may occur In the localized pattern, the affected demonstrate horizontal rows of pits a linear depression. The altered area is located in the middle third of the buccal surface of teeth. The type IC is more severe and typically demonstrate involvement of all teeth in both dentitions In type ID the enamel of all teeth exhibits a smooth surface and is thin hard and glossy Anterior open bite is seen and teeth exhibit a thin peripheral outline of radiopaque enamel on radiograph In type IE this is a lesion showing lionization effect. In females the teeth would exhibit alternating zones of normal and abnormal enamel. Males exhibit diffuse thin, smooth and shiny enamel in both dentitions. The teeth have the shape of crown formation with open contacts. In the rough pattern, the enamel is thin, hard and rough surfaces. An anterior open bite is common. In enamel agenesis demonstrate total lack of enamel. The teeth are the shape and color of the dentin. The surface is rough. Dentin defects b. Dentinogenesis imprfecta A hereditary developmental disturbance of the denitn in the absence of any systemic disorder. This is an autosomal dominant condition affecting both deciduous and permanent teeth. Affected teeth are gray to yellowish brown and are tulip shaped. Genetic studies show that the gene defective maps to chromosome 4 in case of type II. It encodes a protein called dentin sialophosphoprotein and constitutes about 50% of the noncolllagenous component of dentin matrix. DI type I is due to mutational changes in gene coding pro alpha 1, pro alpha 2 chains of type I collagen, major protein of organic matrix in bone and dentin. Recent studies report that type II and type III arise from a single mutation of DSPP gene and that these are not separate disease but rather phenotypic variation of a single disease. Acc. to Sheild’s classification DI type I – osteogenesis imperfecta with opalescent teeth DI type II – isolated opalescent teeth DI type III – isolated opalescent teeth Brandywine Extensive studies have proven that DI is a disorder distinct from Osteogenesis imperfects so a revised classification is proposed DI type I corresponds to type II of Sheild’s Type II corresponds to type III of Sheild’s There is no substitute for type I of Sheild’s classification Clinical and radiographic features deciduous teeth are affected most severely followed by the permanent incisors and first molars enamel is normal but separates easily from dentin because of defective dentinoenamel junction once exposed the dentin often demonstrates significantly accelerated attrition radiographically, the teeth have bulbous crowns cervical constriction thin roots and early obliteration of the root canals and pulp chambers. Type III has shell teeth demonstrating normal thickness enamel in association with extremely thin dentin and dramatically enlarged pulps Histologic features The dentin adjacent to the enamel junction appears similar to normal dentin but the remainder is distinctly abnormal Short tubules course through an atypical granular dentin matrix which often demonstrates interglobular calcificaiton. Cells can be seen entrapped within the defective dentin Anomalies of apposition Enamel defects a. amelogenesis imperfecta type II IV AI type II – hypomaturation the enamel matrix is laid down appropriately and begins to mineralize however there is a defect in the maturation of the enamel crystal structure Classified into Type IIA – hypomaturation, pigmented AR Type IIB – hypomaturation, X linked recessive Type IIC – snow capped teeth, AD Genetic studies show that multiple mutations in the AMELX gene in the type IIA AI whereas IIA C the gene defect is unknown. Clinical features Affected teeth are normal in shape but exhibit a mottled, opaque white brown yellow discoloration. The enamel is softer than normal and tends to chip from the underlying dentin. Radiographically the affected enamel exhibits a radiodensity that is similar to that of dentin. Type IIA the surface enamel is mottles and agar brown. Enamel is soft enough to be punctures by an explorer Type IIB shows lionization that is male exhibit differebti pattern in deciduous and permanent teeth. The deciduous teeth are opaque white with a translucent mottling; the permanent teeth are opaque and may darken with age. Female patients exhibit a similar pattern in both dentitions. The teeth demonstrate vertical bands of white opaque enamel and normal translucent enamel. Radiographically the bands are not perceptible. Type IIC exhibits a zone of white opaque enamel on the incisal or occlusal third of the crown. AI type IV – hypomaturation hypoplastic with taurodontism This type of Ai exhibit enamel hypoplasia in combination with hypomaturation. Classified into Type IV A hypomaturation hypoplastic Type IVB hypoplastic hypomaturation Genetic defects in both groups is unknown Type IV A the predominant defect is one of enamel hypomaturation in ehich the enamel appears mottled yellowish white to yellow brown. Pits are seen frequently on the buccal surface of the teeth. Radiographically the enamel is similar to dentin in density and large pulp chambers may be seen in addition to varying degree of taurodontism Type IVB the predominant defect is one of enamel hypoplasia in which the enamel is thin; the enamel that is present demonstrates hypomaturation. Radiographically there is decrease in the thickness of the enamel. Both these types are seen in the systemic disorders, trich dento osseous syndrome. Other features seen are kinky hair, osteosclerosis and brittle nails. b. enamel pearl Refers to the presence of enamel in unusual locations mainly the tooth root. These are hemispheric structures that may consist entirely of enamel or contain underlying dentin and pulp tissue. These are thought to arise from a localized bulging of the odontoblastic layer. This bulge may provide prolonged contact between Hertwig’s root sheath and the developing dentin, triggering induction of enamel formation. t is found most frequently on the roots of maxillary molars. The enamel pearls precludes normal PDL attachment with CT. Dentin defects c. dentin dysplasia It is a rare disturbance of dentin formation characterized by normal enamel but atypical dentin formation with abnormal pulpal pathology. It is an abnormality that maps to the same site on ch 4 as does DI type II III. It too may be an allelic variant. Cl assified into Type I radicular dentin dysplasia Type II coronal dentin dysplasia Both these patterns appear to be hereditary diseases, transmitted as an autosomal dominant characteristic. Clinical features Type I both dentitions are affected although the teeth are clinically normal. The teeth are extremely mobile and exfoliated prematurely Type II both dentitions are affected. Deciduous teeth have the same color as that in DI but the permanent dentition is normal. Type I both dentitions roots are short blunt and conical. In deciduous pulp chambers and root canals are completely obliterated. Permanent teeth crescent shaped pulpal remanant remains. Periapical radiolucencies involving intact teeth are present. Type II deciduous dentition presents with completely obliterated pulp chambers. Permanent teeth exhibit an abnormal large pulp chamber in the coronal portion. Histologic features Type I a portion of coronal dentin is normal. Most of the pulp is obliterated by calcified tubular dentin, osteodentin and fused denticles. New dentin forms around these obstacles giving the characteristic appearance described as Lava flowing around the boulders. Type II deciduous tee th exhibit amorphous and atubular dentin in the radicular portion while coronal dentin is normal. Permanent teeth same but the pulp has multiple pulp stones. d. regional odontodysplasia It is a localized non hereditary development abnormality of teeth with extensive adverse effects on the formation of enamel, dentin and pulp. Proposed causes abnormal migration of neural crest cells latent virus local circulatory deficiency local trauma or infection hyperpyrexia malnutrition radiation therapy somatic mutation pathosis associated with RO ectodermal dysplasia epidermal nevi hypophosphatasia hydrocephalus neurofibromatosis Rh incompatibility Vascular nevi Clinical features maxillary teeth esp anterior are most commonly affected female predilection with a ratio of 1. 4:1 the affected teeth fail to erupt and their shape is markedly altered the erupted teeth show small irregular crown that is yellow to brown with rough surface on x ray they have a very thin enamel and dentin surrounding an enlarged radiolucent pulp There is lack of contrast between enamel and dentin. Histologic features marked reduction in the amount of dentin and widening of predentin layer presence of large areas of interglobular dentin and an irregular pattern if dentin the reduced enamel epithelium around nonerupted teeth show many irregular calcified bodies known as enameloid conglomerates (also seen in AI) e. hypercementosis It is a nonneoplastic deposition of excessive cementum that is continous with normal radicular cementum Clinical and radiographic features in x ray affected teeth demonstrate a thickening or blunting od the root the enlarged root is surrounded by the radiolucent PDL space and intact dental lamina may be isolated or involve many teeth premolars are involved more frequently predominantly in adults and the frequency increases with age factors associated with hypercemntosis i. local 1. abnormal occlusal trauma 2. adjacent inflammation 3. unopposed teeth ii. systemic 1. acromegaly 2. arthritis 3. alcinosis 4. paget’s disease 5. rheumatic fever Histologic features periphery of root exhibits deposition of an excessive amount of cementum this may be hypocellular or ostecementum the material is arranged in concentric layers Anomalies of mineralization a. amelogenesis imperfecta type III hypocalcifeid in this type the enamel matrix is laid down appropriately but no significant mineralization occurs. Classified into Type III A – autosomal dominant Type IIIB – autosomal recessive In both gene defect is unknown. Most common type of AI. Teeth are norma on eruption but the enamel is very soft and easily lost. Enamel is yellow brown on eruption and turns to brown black due to staining. Autosomal recessive are more severe than the dominant type. Radiographically the density is similar for both enamel and dentin. CONCLUSION An understanding of the many disturbances of development of teeth is predicated upon s thorough understanding of the embryology of these structures. Genetic factors are undoubtedly of importance in the development of these defects. REFERENCE: ? Oral pathology by Shafer ? Oral pathology by Somes and Southam ? Oral maxillofacial pathology by Naville ? Developmental defects of teeth by www. UNC DENTISTRY. com ? Oral histology by Orban’s ? Oral histology by Tencates ? Normal and abnormal dental development- by Isabelle Miletich Paul T. Sharpe Human Molecular Genetics, 2003. ? Mouse models of tooth abnormalities Eur J Oral Sci 2008; 116: 1–10

Gone in 60 Seconds essays

Gone in 60 Seconds essays Gone in 60 Seconds reunites actor Nicolas Cage with producer Jerry Bruckheimer. The two are known for some of the best action movies ever, including The Rock and Con Air. Gone in 60 Seconds carries on that very same tradition with fast high speed action and fast high speed car chases. Gone in 60 Seconds tells the story of Randall Memphis Raines (Cage), a retired car thief who has given up the life of crime and has settled down. His younger brother (Ribisi), is still very much into the car stealing scene, and has gotten himself into trouble with his boss by botching a high priced boost. The boss then sends an ultimatum to Memphis: either he comes back to the business and lifts 50 cars in 4 days, or his brother dies. Memphis decides to return to his former profession for the sake of his brother, and gathers some old friends and forms a crew of car boosting experts. The chemistry between most of the characters works. Cage plays the protective older brother to Ribisi, a kid whos gotten into the life too deep and finds himself in more trouble than he can handle. Robert Duvall is the veteran who masterminds the whole The supporting cast is there for some comic relief. They fill the movie with many cliches and stereotypes. Ribisis young friends are the exact opposite of Cages crew. They are using their new high tech gadgets to steal cars for the money, unlike Cage and his crew who do it for the rush. In one of the funnier scenes, a member of Cages team is car-jacked while he is driving away with a stolen car. Instead of surrendering, he curses, gets out of his car, beats down the car-jacker, and lectures him that hes an amateur who doesnt know the first thing about reall ...

Mixture Definition and Examples in Science

Mixture Definition and Examples in Science In chemistry, a mixture forms when  two or more substances are combined such that each substance retains its own chemical identity. Chemical bonds between the components are neither broken nor formed. Note that even though the chemical properties of the components havent changed, a mixture may exhibit new physical properties, like boiling point and melting point. For example, mixing together water and alcohol produces a mixture that has a higher boiling point and lower melting point than alcohol (lower boiling point and higher boiling point than water). Key Takeaways: Mixtures A mixture is defined as the result of combining two or more substances, such that each maintains its chemical identity. In other words, a chemical reaction does not occur between components of a mixture.Examples include combinations of salt and sand, sugar and water, and blood.Mixtures are classified based on how uniform they are and on the particle size of components relative to each other.Homogeneous mixtures have a uniform composition and phase throughout their volume, while heterogeneous mixtures do not appear uniform and may consist of different phases (e.g., liquid and gas).Examples of types of mixtures defined by particle size include colloids, solutions, and suspensions. Examples of Mixtures Flour and sugar may be combined to form a mixture.Sugar and water form a mixture.Marbles and salt may be combined to form a mixture.Smoke is a mixture of solid particles and gases. Types of Mixtures Two broad categories of mixtures are heterogeneous and homogeneous mixtures. Heterogeneous mixtures are not uniform throughout the composition (e.g. gravel), while homogeneous mixtures have the same phase and composition, no matter where you sample them (e.g., air). The distinction between heterogeneous and homogeneous mixtures is a matter of magnification or scale. For example, even air can appear to be heterogeneous if your sample only contains a few molecules, while a bag of mixed vegetables may appear homogeneous if your sample is an entire truckload full of them. Also note, even if a sample consists of a single element, it may form a heterogeneous mixture. One example would be a mixture of pencil lead and diamonds (both carbon). Another example could be a mixture of gold powder and nuggets. Besides being classified as heterogeneous or homogeneous, mixtures may also be described according to the particle size of the components: Solution: A chemical solution contains very small particle sizes (less than 1 nanometer in diameter). A solution is physically stable and the components cannot be separated by decanting or centrifuging the sample. Examples of solutions include air (gas), dissolved oxygen in water (liquid), and mercury in gold amalgam (solid), opal (solid), and gelatin (solid). Colloid: A colloidal solution appears homogeneous to the naked eye, but particles are apparent under microscope magnification. Particle sizes range from 1 nanometer to 1 micrometer. Like solutions, colloids are physically stable. They exhibit the Tyndall effect. Colloid components cant be separated using decantation, but may be isolated by centrifugation. Examples of colloids include hair spray (gas), smoke (gas), whipped cream (liquid foam), blood (liquid),   Suspension: Particles in a suspension are often large enough that the mixture appears heterogeneous. Stabilizing agents are required to keep the particles from separating. Like colloids, suspensions exhibit the Tyndall effect. Suspensions may be separated using either decantation or centrifugation. Examples of suspensions include dust in air (solid in gas), vinaigrette (liquid in liquid), mud (solid in liquid), sand (solids blended together), and granite (blended solids). Examples That Are Not Mixtures Just because you mix two chemicals together, dont expect youll always get a mixture! If a chemical reaction occurs, the identity of a reactant changes. This is not a mixture. Combining vinegar and baking soda results in a reaction to produce carbon dioxide and water. So, you dont have a mixture. Combining an acid and a base also does not produce a mixture. Sources De Paula, Julio; Atkins, P. W.  Atkins Physical Chemistry  (7th ed.).Petrucci R. H., Harwood W. S., Herring F. G. (2002).  General Chemistry, 8th Ed. New York: Prentice-Hall.Weast R. C., Ed. (1990).  CRC Handbook of chemistry and physics. Boca Raton: Chemical Rubber Publishing Company.Whitten K.W., Gailey K. D. and Davis R. E. (1992).  General chemistry, 4th Ed. Philadelphia: Saunders College Publishing.