This soot is mainly carbon black but contains a significant amount of C60 carbon cluster compound, in this process smaller amounts of other fullerenes C32, C50, C70, C76 and C84 may also be produced. State whether the solutes and solvents in the following combination are miscible or immiscible. aqueous solution It can catalyse photochemical refining in industry. Is Lube safe to go inside? Learn about financial support for future and current high school chemistry teachers. The pentacarbonyl species are produced by photochemical reactions. They are made up of large molecules so are not classed as giant covalent networks . As for the name, buckminsterfullerene, Curl only says, Harry was convinced that was his idea and Rick was convinced it was his idea and I'm convinced it wasn't my idea. In contrast to chemicallyeither covalently or noncovalentlymodified fullerenes, some C60 derivatives can be highly toxic. I went back to my desk, Smalley says, cut a single pentagon from the legal paper and began sticking pentagons around it. Furthermore, under light exposure, C60 is an efficient singlet oxygen sensitizer. Because of its high electronic affinity[47] it is one of the most common electron acceptors used in donor/acceptor based solar cells. 's history reveals that she had 1 preterm delivery 4 years ago at 31 weeks gestation. Smalley, Great Balls of Carbon, p. 23; see also, Baggott, Ibid. The different compounds are separated by chromatographically. [53], An experiment in 20112012 administered a solution of C60 in olive oil to rats, achieving a major prolongation of their lifespan. How the name buckminsterfullerene came about. Fullerene Uses & Applications - How Are C60 Buckyballs Useful C60 fullerene cannot conduct electricity. The discovery of fullerenes also led to research in carbon nanotubes, the cylindrical cousins of buckyballs, and the development of new fields of advanced materials. Flashcards. She has no other risk factors for preterm labor. Thanks for reading Scientific American. C60 films and solution have strong non-linear optical properties; in particular, their optical absorption increases with light intensity (saturable absorption). ChemLuminary Awards Molecules of C 60 are spherical. Under various conditions a vast number of halogenated derivatives of C60 can be produced, some with an extraordinary selectivity on one or two isomers over the other possible ones. Carbon nanotubes' unique structural and bonding properties, whereby inner tubes in a multi-walled nanotube can slide within an outer tube, suggest uses in tiny motors and as ball bearings and lubricants. membered carbon rings. Landmark Lesson Plan: Discovery of Fullerenes. Each six membered rings is surrounded, alternately, by hexagons and pentagons of carbons; each pentagon is fused to five hexagons. That is not to say that such products will not ever exist. Theo Mid Term Incommunicable attributes of God. Curl, who brought a healthy dose of skepticism to the entire project, doubted whether hexagons alone would do the trick.20, With the daytime discussion seemingly reaching a dead end, part of the group went to a favorite Mexican restaurant to celebrate the discovery of C60.21 During the meal, Smalley wondered how a sheet of hexagons could close; perhaps, the only way to find out was to build one.22, Smalley worked into the night at his home computer trying to generate a structure. Silver nanoparticles are sometimes used in socks to prevent foot odour. Your Mobile number and Email id will not be published. Therefore, among carbon allotropes, graphite is the best conductor of electricity. Does buckminsterfullerene conduct electricity? 2006. Is C60 harmful? Fullerenes may also be used in pharmacy for the creation of new pharmaceuticals. For example, in C60Br8 and C60Br24, the Br atoms are in 1,3- or 1,4-positions with respect to each other. If youre not familiar with Buckyballs, also known as Zen Magnets and Neoballs, theyre small balls made of neodymium magnets. Buckyballs are spheres or squashed spheres of carbon atoms. Each carbon atom is bonded to three others and is sp2 hybridised. Where does the name buckminsterfullerene come from? The encapsulated atoms have been shown to perform circular motions inside the C60 cage, and their motion has been followed using NMR spectroscopy. Why Is Buckminsterfullerene A Good Lubricant - Home Life Answers In 1984 Richard Smalley found himself less than thrilled when he received a request from Harry Kroto, a chemist at the University of Sussex, to use equipment in Smalleys laboratory at Rice University to study a special kind of carbon molecule.1, In retrospect, Kroto writes, I seem to have been fascinated by various peculiar aspects of carbon chemistry for much of my research career.2 Kroto wanted to investigate the origins of the long linear carbon chain molecules that he, together with Canadian radio astronomers, had discovered in interstellar space several years earlier. Shown from left to right: Sean OBrien, Richard Smalley, Robert Curl, Harry Kroto and James Heath. The C60 molecule undergoes a wide range of novel chemical reactions. Which is an incorrect statement about buckminsterfullerene? Weak intermolecular forces exist between individual buckyballs. Save my name, email, and website in this browser for the next time I comment. Kagaku (Kyoto) (in Japanese). The hard part has been thinking up such a unique application for fullerenes. Please refer to the appropriate style manual or other sources if you have any questions. Copyright 2022 Home Life Answers All Rights Reserved Noveladd, Why Is Buckminsterfullerene A Good Lubricant. Millimeter-sized crystals of C60 and C70 can be grown from solution both for solvates and for pure fullerenes. volumes (accurately), always beware anomalies when you have to calculate averages Your Mobile number and Email id will not be published. A lubricant is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. The midpoint potentials of 1-electron reduction of buckminsterfullerene and its anions is given in the table below: C60 forms a variety of charge-transfer complexes, for example with tetrakis(dimethylamino)ethylene: This salt exhibits ferromagnetism at 16K. C60 oxidizes with difficulty. Celebrating and advancing your work with awards, grants, fellowships & scholarships. Reaction of C60 with 9,9,10,10-dihydroanthracene under the same conditions, depending on the time of reaction, gives C60H32 and C60H18 respectively and selectively. This change is associated with a first-order phase transition to an fcc structure and a small, yet abrupt increase in the lattice constant from 1.411 to 1.4154nm.[38]. allow to evaporate / crystallise at Fullerenes consist of some single bonds and some double bonds. The C60 molecule has the highest possible symmetry (icosahedral) and assumes the shape of a soccer ball. ACS-Hach Programs Fullerene in its pure state acts as insulators but can be converted to semiconductors and superconductors under suitable conditions. Questions like the one posed here challenge the materials researcher and the R&D community to take advantage of a new opportunity. The compound was discovered in 1985 and has received intense study, although few real world applications have been found. Applications of Fullerenes C60 The basis of these Batteries is lithium cathodes. The AZo Journal of Materials Online. These need little energy to overcome, so buckminsterfullerene is slippery and has a low melting point. Thus, fullerene may be highly useful in preventing many skin problems related to oxidative stress. They chose the imaginative name buckminsterfullerene for the cluster in honour of the designer-inventor of the geodesic domes whose ideas had influenced their structure conjecture. In addition, evidence was obtained for the existence of other smaller metastable species, such as C28, C36, and C50, and experimental evidence was provided for endohedral complexes, in which an atom was trapped inside the cage. Addition of fluorine and chlorine usually results in a flattening of the C60 framework into a drum-shaped molecule. Specially, when fluorine is attached on the exterior which increases the ability of its round shape. volume (accurately) They start rotating at about 20C. , What errors can you come across when reading a thermometer, How many Hydrogen atoms in the formula 4H3O2. All known carbon-containing molecules, even benzene, a very stable ring of carbon atoms, have edges that terminate with other elements. This is how they can carry drug molecules around the body and deliver them to where they are needed, and trap dangerous substances in the body and remove them. These need little energy to overcome, so buckminsterfullerene is slippery and has a low melting point. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); 2023 FAQS Clear - All Rights Reserved reacts Why do you think a diamond is so hard and graphite is so soft? What is the structure of buckminsterfullerene? During the period 1985-1990, the Curl/Smalley team at Rice and Kroto at Sussex managed to amass a wide range of circumstantial evidence to support the fullerene structure proposal. They are excellent conductors of heat and electricity, and they possess an astonishing tensile strength. C. 60. : Buckminsterfullerene. [See Figure 6] Some scientists therefore had hoped that it could be used as a lubricant, but tests have proved unsuccessful, and most scientists now feel that it is a dead end (4). Graphene has the following properties: It is extremely strong but also amazingly light. In this building in early September 1985, a team of scientists discovered a previously unknown pure carbon molecule, C60, which they dubbed buckminsterfullerene. Curl told Kroto about his collaboration with Smalley in studying atom clusters in Smalleys machine. Network with colleagues and access the latest research in your field, ACS Spring 2023 Registration One thing became apparent: C60 formed very readily and exhibited extraordinary stability; in one instance, AP2 produced forty times more C60 than either C58 or C62 carbon clusters.15, What was the structure of these clusters? Why does buck ministerfullerene act as a good lubricant 1 See answer Advertisement najaboo34 Its molecules are made up of 60 carbon atoms joined together by strong covalent bonds. She states that she feels occasional uterine cramping and does not believe that her membranes have ruptured. Herein,why do fullerenes make good lubricants? Kroto and Smalley thought hexagons made up the surface of geodesic domes. [45], Metal atoms or certain small molecules such as H2 and noble gas can be encapsulated inside the C60 cage. Graphene occurs as sheets of carbon while fullerene occurs as spheres of carbon. All the 60 carbon atoms are equivalent and give rise to a single 13C NMR resonance. The fullerenes constitute a third form, and it is remarkable that their existence evaded discovery until almost the end of the 20th century. Who Can Benefit From Diaphragmatic Breathing? There are two major families of fullerenes, with fairly distinct properties and applications: the closed buckyballs and the open-ended cylindrical carbon nanotubes. molecules are spherical (so molecules) will roll Silver nanoparticles are sometimes used in socks to prevent foot odour. Their hollow structure could make them useful for delivering medicine in the future. It can be used as radical scavenger and antioxidant. Although they are fascinating from a purely scientific point of view, their utilitarian value is not so clear. Give two factors that affect the voltage produced by a cell. Research on fullerenes has resulted in the synthesis of a steadily increasing number of new compounds, already more than one thousand. Figure 5 For example, one direct outcome of fullerene research has been the discovery of carbon-based nanotubes. This experiment also could be a preliminary pilot for a rather more complicated experiment that might solve a long-standing puzzle in astronomythe carriers of the mysterious and now legendary diffuse interstellar bands. Kroto and Smalley later disagreed on which one of them pushed the idea at first and who came up with the eventual name for C60. This is the structure. Their discovery lead to a Nobel Prize in 1996. This allows them to flow at very high speed, giving graphene a very high level of electrical conductivity. The presenter of the Nobel noted that the discovery of fullerenes has implications for all the natural sciences. Why does buck ministerfullerene act as a good lubricant Mass spectrometry has been widely used to study the fullerenes. Fullerenes are a class of inorganic carriers, these molecules are preferred as they show good bio compatibility, greater selectivity, retain the biological . It is flexible. _____ Knowledge awaits. It has expanded knowledge of chemistry and physics. - Meaning it has a low melting point and is slippery. Who discovered fullerene? - TimesMojo Their hollow structure could make them useful for delivering medicine in the future. The Exxon scientists, Eric Rohlfing, Donald Cox, and Andrew Caldor, had used a machine, similar to the AP2, built by Smalleys group at Rice. Molecules of C 60 are spherical. Answer in terms of structure and bonding. Their discovery lead to a Nobel Prize in 1996. Buckyballs are good lubricants because of their spherical shape. In 1996, Robert Curl, Harold Kroto, and Richard Smalley won the Nobel Prize in Chemistry for the discovery of the fullerenes. What is special about buckminsterfullerene? addition with hydrogen to give polyhydrofullerenes. 2 : something that lessens or prevents friction or difficulty a social lubricant. Uncover the Chemistry in Everyday Life. A federal judge overturned a 2012 ban on the sale of the toy, meaning its now legal to sell them in the U.S. again. Fullerene is a hollow sphere, and it also has other shapes. There are weak intermolecular forces between molecules of buckminsterfullerene. The blue "Buckyballs" are sandwiched between two metal surfaces. It seems to be that the history of fullerenes research is very short. Why is a buckminsterfullerene a good lubricant? Fullerenes are a remarkable class of molecules in which large numbers of carbon molecules are locked together into a roughly spherical shape. (but) burette measures variable As a result Buckminsterfullerene doesnt conduct electricity. Discovery of Fullerenes. See, Aldersey-Williams. "The Discovery of Fullerenes" commemorative booklet produced by the National Historic Chemical Landmarks program of the American Chemical Society in 2010 (PDF). C60 also undergoes Birch reduction. Despite their unusual name and their relatively short time on the research scene, there are many possible fullerene uses.Fullerene uses could be infinite Antioxidants. It can also be used as a storage for hydrogen atoms. Weaver describes the current thinking on this topic: "There has been considerable interest in practical applications for fullerenes (buckyballs) since Wolfgang Kratschmer and Donald R. Huffman first demonstrated a way to produce these molecules in quantity (see their article in Nature, Vol. in solution Alkali metals and alkaline earth metals as well as early lanthanoids may be trapped by vaporizing graphite disks or rods impregnated with the selected metal. These all-carbon molecules captured the attention of scientists and laymen alike and generated considerable coverage by the popular press. Although in each molecule every carbon is only covalently bonded to 3 others and the other electrons are delocalised, these electrons cannot jump between different molecules. Taubes, The Disputed Birth of Buckyballs, p. 1477. 1155 Sixteenth Street, NW, Washington, DC 20036, USA |service@acs.org|1-800-333-9511 (US and Canada) | 614-447-3776 (outside North America), Copyright 2023 American Chemical Society. [43] Phenyl-C61-butyric acid methyl ester derivative prepared through cyclopropanation has been studied for use in organic solar cells. A 1994 study published by Chinese Physics Letters observed the biological impact of a water-soluble C 60 liposome on human cervix cancer cells. Why are fullerenes used for drug delivery? heat with an electric heater It took years, for example, to move from the first demonstration of semiconductor-based electronic devices to transistors and integrated circuits in commercial products. Years have passed since the discovery of Buckminsterfullerene. Properties of Graphene. The structure, a truncated icosahedron with 32 faces, 12 pentagonal and 20 hexagonal, has the shape of a soccer ball. , possibly as a fuel tank for fuel cell powered cars. They write new content and verify and edit content received from contributors. Suggest why Buckminsterfullerene is a good lubricant. Why Is Buckminsterfullerene A Good Lubricant. Carbon, the basis of life, is one of the most common elements and one of the most studied; it comprises the whole discipline of organic chemistry. These OBBs are created by binding atoms of a transition metal (TM) to C60 or C48B12 and then binding many hydrogen atoms to this TM atom, dispersing them evenly throughout the inside of the organometallic buckyball. - slippery and can be used as a lubricant as there are weak forces of attraction between layers - high melting point . Reactions of C60 with free radicals readily occur. John H. Weaver is the head of the Electronic Materials Group in the department of chemical engineering and materials science at the University of Minnesota; he was recently named 1997 Scientist of the Year by R&D Magazine. It is what is called an "allotrope" of carbon, the others being diamond, graphene, and graphite. The C60 molecules can also be coupled through a [2+2] cycloaddition, giving the dumbbell-shaped compound C120. C60 Buckballs as a lubricant - Stock Image - A700/0033 Use Figure 1 . Their cage structure and poly aromaticity cause the formation of a displaced electron cloud that allows these molecules to act as charge-transfer complexes. 8 Useful Applications of Fullerenes You'll Be Surprised to Know A lubricant is a substance which introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. The fullerene molecule was discovered by Richard Smalley. When alkali metals are doped into these voids, C60 converts from a semiconductor into a conductor or even superconductor. Such properties hold the promise of exciting applications in electronics, structural materials, and medicine. Their construction roughly resembles the interlocked trusses of Buckminster Fuller's famous geodesic domes, which is why these molecules are called fullerenes or buckyballs. Do buckyballs have delocalised electrons? Who invented buckminsterfullerene? Why is buckminsterfullerene used to deliver drugs? Its molecules are made up of 60 carbon atoms joined together by strong covalent bonds. A later research confirmed that exposure to light degrades solutions of C60 in oil, making it toxic and leading to a "massive" increase of the risk of developing cancer (tumors) after its consumption. Flashcards. Your email address will not be published. Though the free electrons are present in the molecules of Buckminsterfullerene they are held by vanderwalls forces. or They can act as hollow cages to trap other molecules. Video Answer: Why is buckminsterfullerene named after Buckminster Fuller? Due to their ability to decrease the transmittance of light, buckminsterfullerenes are able to be used as optical limiters. Why Are Fullerenes Good Lubricants - It Is All about Their Structure The Early Experiments Proved Fullerenes Additives Could Significantly Improve the Performance of Lubricants Providing a Proof What Are the Properties of Fullerene Lubricant? Suggest why it is cheaper to use nanoparticles of silver rather than coarse particles of silver. Carbon nanotubes are very strong and light, and can act as semiconductors or conductors. [40] Fcc C60 contains voids at its octahedral and tetrahedral sites which are sufficiently large (0.6 and 0.2nm respectively) to accommodate impurity atoms. This site is using cookies under cookie policy . The consequence of this structural motif is that each hexagon is like the base of a bowl; the three pentagons fused to this ring, linked by hexagons, force the structure to curve resulting in a dome-like structure that eventually curves around itself to give a structure resembling a sphere. The name was chosen because the geodesic domes of Buckminster Fuller provided a clue that the molecules atoms might be arranged in the form of a hollow cage. At dinner were Kroto, Smalley, Heath and Heaths wife. Three reversible oxidation processes have been observed by using cyclic voltammetry with ultra-dry methylene chloride and a supporting electrolyte with extremely high oxidation resistance and low nucleophilicity, such as [nBu4N] [AsF6].[42]. At first, the group referred to it as a wadge, a British term for a handful of stuff, with Smalley referring to the mother wadge, Kroto to the godwadge.14, Since Kroto was scheduled to return to England early the following week, Heath and OBrien spent the weekend trying to plumb the mystery molecules properties. There are two major families of fullerenes, with fairly distinct properties and applications: the closed buckyballs and the open-ended cylindrical carbon nanotubes. These need little energy to overcome, so buckminsterfullerene is slippery and has a low melting point. Why do fullerenes make good lubricants? There are weak intermolecular forces between molecules of buckminsterfullerene. For example, looking back a decade on the discovery of superconductivity in the cuprates (copper-containing materials that transport electricity without resistance at relatively high temperatures), it was clear from the beginning that these materials would find markets in current-carrying applications, once costs and technical problems were overcome. What is the thermal conductivity of buckminsterfullerene? Researchers generally tried to be optimistic while remaining circumspect and cautious--who, after all, can see the future clearly? Your email address will not be published. http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/fullerenes.html (accessed Month Day, Year). When You Breathe In Your Diaphragm Does What? Complexes have been reported molybdenum, tungsten, platinum, palladium, iridium, and titanium. fullerene, also called buckminsterfullerene, any of a series of hollow carbon molecules that form either a closed cage (buckyballs) or a cylinder (carbon nanotubes). So it has five membered rings less than six membered rings. This is how they can carry drug molecules around the body and deliver them to where they are needed, trap dangerous substances in the body and remove them. You can specify conditions of storing and accessing cookies in your browser. Experiments showed that the size of an encapsulated atom determined the size of the smallest surrounding possible cage. Molecules of C 60 are spherical. Suggest why Buckminsterfullerene is a good lubricant. Buckminster fullerene, C60(s)is NOT a network solid. A lubricant is a substance that allows materials to move over each other easily. Match. What is the expected daily profit if a store sells X air conditioners per day with probability f(10)=0.1, f(11)=0.3, f(12)=0.4, f(13)=0.2 and the profit per conditioner is $55? Conversion efficiencies up to 5.7% have been reported in C60polymer cells.[48]. Suggest why Buckminsterfullerene is a good lubricant. Therefore, C60 can undergo addition with hydrogen to give polyhydrofullerenes. The Exxon team found that carbon clusters of more than forty atoms tended to be an even number for some reason. The consequence of this structural motif is that each hexagon is like the base of a bowl; the three pentagons fused to this ring, linked by hexagons, force the structure to curve resulting in a dome-like structure that eventually curves around itself to give a structure resembling a sphere. What is the mass of 7.28 mol of copper (II) nitrate. In this building in early September 1985, a team of scientists discovered a previously unknown pure carbon molecule, C60, which they dubbed buckminsterfullerene. [38][41], C60 undergoes six reversible, one-electron reductions, ultimately generating C660. The next morning, on the way to Rice, Smalley called Curl, asking him to assemble the team in Smalleys office. (so) iodine could not be filtered The students ran the machine with Kroto directing the experiments. remember cm3 is a ml and dm3 is almost a litre, AQA GCSE Physics (9-1) Topic 3 - Particle Mod. Antiviral agents. 1 : a substance (such as grease) capable of reducing friction, heat, and wear when introduced as a film between solid surfaces. A study of pure carbon would not seem all that exciting to most chemists. Little energy is needed to overcome these forces, so substances consisting of buckyballs are slippery and have lower melting points than graphite or diamond . nquainoox. A closed structure, a cage, would have no dangling bonds.17, None of the scientists on the team remembers who first suggested a caged structure. In 1996 the trio was awarded the Nobel Prize for their pioneering efforts. Buckyballs are spheres or squashed spheres of carbon atoms. Bertrand Russell & Buckminster Fuller on Why We Should Work Less, and Then Kroto remembered a stardome he once made for his children; he told Smalley it had pentagonal facets as well as hexagonal ones, but he was unsure. Buckyballs are good lubricants because of their spherical shape. Graphene also has two-dimensional Dirac-like excitations. Spheroids dominated the discussion. On the importance of carbon and its frequency of study, see Hugh Aldersey-Williams, Harold Kroto, Symmetry, Space, Stars and C, Smalley later wrote: To test the theory he [Kroto] wanted to reproduce the stellar conditions in the laboratory, and he knew Rice had the machinery to prove it. Smalley, Great Balls of Carbon, p. 22; Kroto describes his visit to Rice in 1984 in Kroto, C. The extrapolated thermal conductivity of C60 is 0.2 W m1 K1, which is a factor of 2 larger than that of PCBM (saturates at 0.075 W m1 K1 beyond 20 nm). For example, radioactive C. Fullerenes help in improving antiwear and anti-friction properties of lubricating oils. The antioxidant properties of buckyballs may be able to fight the deterioration of motor function due to multiple sclerosis. Explore Career Options ; Kroto says he pinched money from his wife in a lecture entitled C. On August 23, before Krotos arrival, Smalley had the students load carbon in the apparatus as a test of the new experiments.10 On September 1, four days after Kroto landed in Houston, the experiments began in earnest. is used as a superconductor below 18K, which means that it carries an electric current with zero resistance. Fullerenes are covalent; hence they are soluble in organic solvents but insoluble in water. Two significant results emerged from the feverish ten days of experiments: first, the team found, as Smalley put it, Krotos long carbon snakes; second, the scientists also observed, again according to Smalley, a previously unknown molecule of pure carbon.11, The lab book for September 2 first notes the unknown molecule. A second laser pulse ionizes the clusters, pushing them into a mass spectrometer, where the clusters are analyzed.4, In 1984, Kroto met Robert Curl, an old friend, at a conference in Austin, Texas. For example motor oil, friction modifier, friction additive, gel, silicons, flourocarbons, ect. [46], Endohedral fullerenes show distinct and intriguing chemical properties that can be completely different from the encapsulated atom or molecule, as well as the fullerene itself. Cyclopropanation of C60 mostly occurs at the junction of 2 hexagons due to steric factors. Fullerene is able to fit inside the hydrophobic cavity of HIV proteases, inhibiting the access of substrates to the catalytic site of enzyme. or ACS Fall 2023 Call for Abstracts, Launch and grow your career with career services and resources. They can act as hollow cages to trap other molecules. [45], The optical absorption properties of C60 match the solar spectrum in a way that suggests that C60-based films could be useful for photovoltaic applications. type of electrode Take action: Nominate a Landmark and Contact the NHCL Coordinator. Able to generate electricity by exposure to sunlight. American Association of Chemistry Teachers, Reactions: Chemistry Science Videos & Infographics, http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/kroto-lecture.html, http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/curl-lecture.html, http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/smalley-lecture.html, http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/presentation-speech.html, The Richard E. Smalley Institute for Nanoscale Science and Technology, Richard E. Smalley, Robert F. Curl, Jr., and Harold W. Kroto. It conducts heat and electricity. Buckminsterfullerene has emerged as a potential therapeutic in the field of cancer diagnosis and treatment.

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