Okay, hello everyone. Previously, we discussed the cross sections for nuclear reactions, particularly for the Newton induced reactions and the charge particle induced reactions. And now, we will discuss how to determine the cross sections experimentally. In fact, when you irradiate a target in an accelerator or a charge or a reactor, how the active atoms are formed or you can even determine the activity. So, if you determine the activity, you can determine the cross sections. So, first let us discuss how to determine how much will be the activity of a reaction product formed when you bombard a target with the neutrons or charge particles. So, let us discuss in detail the irradiations in the facilities like nuclear reactor and an accelerator. So, let us first discuss the nuclear reactor. So, in nuclear reactor, you will have the neutrons all along the moderator system. So, you will have a sea, it is like a sea of neutrons, large amount of neutrons just diffusing through the medium. And so, when you have a sample, the sample dimension may be 1 centimeter cube or so on. Where is the nucleus, neutrons are there all along in a, you may just say about the meter cube. So, it is like a sea of neutrons and you put a target, the entire target, all the atoms target are exposed to the neutrons. So, the nuclear reactor, so, how do you define, how many neutrons are there in the reactor? You define in terms of plots. So, across when you are having a neutron in the reactor, we say this many neutrons are passing through a 1 centimeter area, 1 centimeter, centimeter square per second. So, you have the neutrons going and 1 centimeter area, how many neutrons are passing in 1 second, that is called the plots. You can actually, we also call this NV sometimes in reactor physics, we call NV, N is the number of neutrons per cc into its velocity. So, neutrons per centimeter cube into centimeter per second. So, it will be neutrons per centimeter square per second. Sometimes the neutrons are not normalized, they are having half component. So, velocities are different. So, you define neutron flux as NV, number of neutrons per cc into velocity of neutrons. So, this is also defined sometimes as neutron flux. So, you irradiate the sample. So, this whole thing is a like a nuclear reactor. Entire target is exposed to neutrons. All the atoms in the target are exposed to neutrons. And so, when you have the target atoms, this is the rate of reaction, target atoms, total terminal target atoms cross section into flux N sigma phi rate of reaction. And when the target is getting activated, then the active atoms start decaying with the rate N lambda. So, the net rate of reaction is N sigma phi minus N lambda. So, this is the, if you are producing a radioactive isotope as a product of a nuclear reaction, then the rate of formation of the, the net rate of formation is Tn by gt, this is the growth minus degree part, like the radioactive decaying. So, Nt is the number of target atoms in the sample. If you have the weight in gram, then you can multiply by the number divided by the mass number, if it is a monoisotropic target. If it is a multi isotropic target, then you have to find the abundance of that isotope. So, in that particular isotope, how many atoms will be there, you have to calculate. So, weight is the weight of target, W is the weight of target in gram, A is the mass number of the target. For example, if it is a monoisotropic like cobalt, A will be 59. But if it is a magnesium target, magnesium, 5, 24, 25, 26, you have to take the average atomic weight, 24. Something. And a particular isotope of magnesium 25, 24, which one is of that you have to accordingly calculate the number of atoms of that target. Sigma is the cross section in terms of centimeter square or 1 and phi is the flux which we define in terms of neutrons per centimeter square per second. So, this if you solve this equation, you get activity at the end of radiation, rate of reaction into 1 minus e raise to minus lambda, Ti, this is called the saturation factor. It will also call this S. So, the saturation factor essentially tells you for how much time you should irradiate the target. There is no point irradiating for a long time. So, you can optimize the irradiation time from this graph. So, actually if you see here, this if you plot this S here, then this factor will become 1. And when Ti equal to Ti equal to 0.5, this is Ti. So, if you irradiate for one half life of the radioactivity that you will produce, you will get 50 percent activity. And after about 3, 4 half lives, you will find that you will saturate the activity. So, you cannot, you do not gain anything by radiating more than 3, 4 half lives. So, usually you irradiate for 1 to 2 half lives of the radioactivity that is sufficient to produce optimum activity. So, this factor is deciding how much is the irradiation time and this decides the rate is formed. So, activity at the end of irradiation will be following again the same graph as the irradiation factor. So, let us do an exercise to know. Now, it is better to get a feel of how many buckles or how many curie we produce when we irradiate certain amount of target. So, that will also tell you how much we can irradiate in this in the reactor. So, let us calculate the activity of cobalt 60, cobalt 60 and gamma 60 cobalt, this is the reactions. 459 is a monobicectopic target, we capture a neutron and by emission of prompt gamma, we come to the ground street of cobalt 60. This ground state will emit, this is the half life of 5.27 year to 60 nickel by emission of 2 gamma is 1172 and 30th. So, I have given a problem here, 1 gram of cobalt is irradiated in Drubar reactor the flux is 510 power 13 neutron per centimeter square per second and time of irradiation is 1 year, half life of cobalt 60 5.27 years. So, this is the equation we use for neutron neutral reactions n sigma 5 the rate of reaction into irradiation factor. So, Nt number of target atoms 1 gram will contain this much upon 59 atoms. So, this many atoms are irradiated sigma 37.2 bonds. So, 37 3.7 minus 23 centimeter square flux is 510 power 13 neutron per centimeter square per second and the saturation factor now 1 minus e raised to minus lambda ti. So, you can write 1 minus e raised to minus 0.693 into time of irradiation 1 hour 1 year on 5.27 years. So, the quantity in exponential has to be dimensionless. So, the time of irradiation and half life should have the same units. If it is in years, then it will be also 3 years. So, we have to take care of the units. So, this factor becomes 0.1236. So, if you multiply these factors, you get activity and the end of irradiation 7.03 10 power 11 factors or 19.01 Q e divide this by 3.7 into 10 power 10. This is the 1 back 1 Q. So, you can see here you irradiate 1 gram of cobalt in a reactor for 1 year and you get about 19 Q e of cobalt 60. So, that gives you an idea the how much activity of cobalt 60 you will get if you irradiate certain amount of cobalt in a reactor for that some amount of time. Now, let us see the irradiation of targets in the accelerator. Unlike in the reactors where we have a pond like a pool like a swimming pool, we have a lot of neutrons moving around and the sample is having very small dimensions. So, all the target atoms are exposed. In the accelerator the target the projectile is a beam of dimensions 1 or 2 millimeters. So, you have a very thin beam of projectile bombarding the target and this is the so this is the vertically you. So, if you have a target like this in a cross sectional area beam will be like this if you see in the perpendicular direction. So, the entire target is not exposed to all the charged particles very small area is exposed to actually the particles and so you normally know the charged particles cannot travel much in the target. So, you use very thin targets of the few microns and if you recall the your lectures on thickness then thickness you write in terms of if it is centimeter then you write rho gram per centimeter cube. So, you write gram per centimeter square, gram per centimeter square is very thick. So, normally you will write milligram per centimeter square. So, in terms of actual thickness it will be in microns. So, because you do not want to stop the beam if the beam will stop it will generate the heat and the energy will be reduced in that. So, you use very thin targets and again how do you produce the activity? So, the rate of production of radioisotopes dn by dt reaction rate n sigma i we do not have the flux now you have a intensity of the targets a projectile minus n lambda a rate at which the radioisotope is decaying and again the solution of it is the similar to that in neutron intrusion reaction rate into saturation fact. Now, that empty the number of target atoms per centimeter square which you can get from the thickness. i is in all that intensity we do not call it a flux, but number of particles per second. So, if you have a target here you put a faraday cup. So, how many particles are heating the faraday cup you can count them. So, you like normally you know when you irradiate you would call it a current beam current will be in nano ampere, micro ampere, milli ampere and so you dump all the beam. So, the particles charge particle will not be stopped in the target they will induce reaction and go ahead with lower energy and will be collected in the faraday cup here. So, you can have the integrated charge and find out how many particles were heating the target and the divide by time you get the particle intensity per second how many particles are heating the target in one second that is what is called the beam intensity. Many times you may have thick target suppose the projectiles energy is not very high then the targetile may stop in the target and then all the beam will be stopped. So, you have to determine the current from the faraday cup this itself can be taken as a faraday cup. So, the saturation factor again 1 minus raised to minus lambda ti will again vary the same way as in the case of neutrons. So, you can decide at what time you should store the irradiation. So, ultimately the formula for the activity of the target the projectile radiostope is again 1 sigma i 1 minus raised to minus lambda ti. Now, let us again do an exercise to see how the activity can be generated in the accelerator irradiation and prior to that it is important to know how to choose the energy of projectile and what energy and what projectile we use to how to produce a particular radiative isotope. So, this is the important exercise to know if you have to produce a particular isotope by charge particle induced reaction what target what projectile and what energy we should use. So, let us give and do an exercise we want to produce thalium 201 which is used in the oncology for the stress test. If someone undergoes some heart problem if the doctor want to know what part of the heart will become intractuous that means the blood is not flowing and you can inject thalium 201 activity and see that we can monitor the activity of this isotope in the blood stream and see whether the heart is receiving the blood all part of the heart is receiving blood or not. So, this isotope we want to produce the reaction that can be used to produce this isotope is thalium 203 P3N proton induced reaction on thalium 203 followed by emission of 3 neutrons giving rise to 201 lead and which is emitting beta minus 2 thalium 201. So, we have proton beam accelerators from aculotrons and now let us see how do we what is the energy of projectile proton that we should be using. So, target is fixed 203 thalium projectile is proton how to fix the energy what energy will give you 201 lead because there are the there are actually the different channels like 3 neutron, 2 neutron, 1 neutron depends upon what the energy brought. So, let us try to see first is the coulomb barrier the proton should cross the coulomb barrier of thalium 203. So, for that we use the reaction the equation R this one this is the factor 1.44 Z1 get to R0 A113 plus A2 one third that is 13.2 is the coulomb barrier. Now, when you bombard thalium with proton 204 lead will be formed and it should be excited such an extent that it should emit 3 neutrons. So, the exercising energy of the compound nucleus that is 204 lead would be sufficiently high emit through typically you know to emit 1 neutron about 10 MeV energy is utilized because the binding energy of neutron in heavy nuclei will be of the row 7, 8 MeV and the neutron will carry some kinetic energy 1, 2, 2 MeV is a total roughly about 10 MeV energy is required to emit any through. So, the exercising energy should be of the row 30 MeV in the compound nucleus so that 3 neutrons are limited. So, the exercising energy of the compound nucleus will be given by ECM plus Q. ECM is the energy available in the center of mass system and Q is the Q value. So, let us calculate the Q value. Q value for this reaction mass of the proton plus mass of thalium 203 minus the mass of 204 lead. So, that is in terms of delta M value the excess mass mass defect values proton thalium 203 and lead 204 these are the delta M into C square values not the actual masses in atomic mass units. So, that becomes plus 6.743 MeV this is the Q value which is positive and as I mentioned for emission of 3 neutrons roughly 10 MeV per neutron that means about 30 MeV should be the exercising energy. So, if 30 MeV is the exercising energy then central mass energy should be ECM plus Q is 30 MeV. So, ECM will be 30 minus 6.73 about 23.2 MeV should be the central mass energy and accordingly the laboratory energy of proton will be ECM into the mass factor mass factors compound nucleus upon target. So, it is slightly different slightly higher than ECM. So, it is 23.37. So, if you take a 23.7 MeV proton beam bombard the thalium 203 target then excess energy of the compound it will be about 30 MeV and by emission of 3 neutrons you will get 201 lead then thereby beta minus decay will lead to 201. So, that is the kind of exercise you can do a priority. In fact, there are no control codes by which you can generate even the cross sections and you can simulate the activity how much activity you will get to irradiate this much intensity. Let us do an exercise for the activity that we can get in the particle induced reaction. So, I have given you an active problem. A 0.01 centimeter thick magnesium foil is irradiated with for 1 hour with deuterium beam of current 100 micro ampere. So, currents will be either nano ampere, macro ampere, milli ampere that can be measured by a factor cup. Calculate the activity of sodium 24 that is produced at the end of bombardment. So, this is the reaction 26 magnesium D alpha 24 sodium and magnesium has got 24, 25, 26 isotopes. Magnesium 26 is about 11 percent hardness and atomic weight of magnesium is 24.3. Now, you have taken 0.01 centimeter thick in terms of milligram per centimeter square. You can multiply by the density 1.74 gram per cc find out the gram. So, you can say 0.01 centimeter into this much gram per cc will give you gram per centimeter square or milligram per centimeter square you can convert. So, the number of target atoms per centimeter square will be thickness into abundance in the Avogadro number upon the atomic weight 4.74 by 19 atoms per centimeter square number of atoms. The current is 100 micro ampere. So, you can see here one coulomb per second is one ampere and so, one electron will give you 1.602 kilo minus 19 coulomb. So, one coulomb per second will be 1 upon 1.602 kilo 990. So, it will be this this will be this many 1 1 ampere it will be 6.24 into 10 power 18 particles per second. So, one ampere gives you 6.24 10 power 18 and if it is micro ampere then 10 power minus 6. So, it will be 6.24 10 power 14 particles per second. So, now, you can see here that the current you can convert into particles per second. Then the saturation factor 1 minus e to the power lambda t i the half life is 14.95 hours for sodium 24 and you are eroding for 1 hour. So, half life would be in the same units half life and eroding time the same it will become 0.045297. So, now, you can calculate the cross section is 25 milliband 1 milliband the power minus 27 centimeter square. So, all of them you can put and you can calculate the activity of sodium 24 or n sigma i that and the saturation factor will be 3.33 and power 7. So, you can see here that in the case of accelerators where the wave intensities are low targets are very thin you get about military levels of activity compared to the curie levels of activity in reactors. So, accelerators we will discuss more on the accelerators this comparing the new reactor radiation and accelerators radiation in general in accelerators we get lower activity because of the the limitations of the target thickness as well as the particle intensity. Now, we have now got the idea what is that level of activity that you can produce. Let us now what we will think discuss the determination of cross section for the charge particle induced reaction. So, let we will take an example of alpha induced reaction on niobium-93 giving rise to compound nucleus-97 and this excited state of nucleus can emit now one neutron, two neutron, three neutron depending upon the excitation energy. So, the variation of the cross section with the energy of the projectile which call as the excitation function. So, we discussed the reaction cross section which is varying as this one sigma r equal to pi r square 1 minus e c upon e c m. So, that is this this is the total reaction cross section, but the compound nucleus that is formed it can emit one neutron at low energy, still high energy can emit second neutron and still high energy it can emit third neutron. So, as you it is the energy of the projectile the compound nucleus is formed with the higher and higher excitation energy and therefore the different channels are opening up the different products are formed depending upon the energy of the projectile. So, therefore, when you are measuring the cross section one needs to measure the total cross section. So, at a particular energy suppose you want to measure the total cross section then you will find at this energy you have one product and two product the sum total of these two will give you the total reaction cross section. So, the excitation functions normally what you do if you do an offline experiment means you radiate the sample you produce reductive isotopes and count in the level three you generate this excitation functions by varying the energy of the projectile. So, for this this measurement what you do you measure the excitation function. Excitation functions means cross section as a function of energy of the projectile sigma e and for that if the products are reductive you can do offline experiment. By offline I mean you radiate the sample in the accelerator from the radiation take out the sample from the accelerator and count the activity in the laboratory on a gamma spectrometry setup and we can form that. So, the same equation is used to find out the cross section. The activity at the end at any time after the radiation is n sigma i sigma is the one we want to determine saturation factor and the after radiation it is maybe decaying with time gamma ray intensity of the isotope and the detection efficiency for counting. So, if you know the target what target you are radiating you know the intensity from the paradigm of radiation you know how much time elapsed after radiation gamma ray intensity and the efficiency if you know you can find out the sigma and the energy at what energy you are going to experiment determined by this. So, what we have here is projectile is bombarding the stack of target and catch. So, this is the target the red ones are the target and the blue ones are the catch. Why this catch is required that when the target is bombarded the products may come out of the target by the coil energy and get stopped in the catch. So, if you do not put this catcher files the products of this target will follow on this target and so on. So, it is important that you stop the required products in the next file which can be a catcher file. This catcher file which also used to reduce the energy of the projectile. So, subsequent you will find 1, 2, 3, 4, 5. The six the five targets will be facing the beam of different energy. So, you have got the cross section measurements at high projectile energies in one of your products. So, this couple you can count them together in the gamma spectrometry setup and measure the activity and from the activity you can find out the process. So, if you are doing the offline experiment for the measurement of radioactive evaporation residue. Evaporation residue means the one after evaporation of neutrons whatever regimes are formed like Technician 97 giving rise to Technician 96, 95, 94. But these products are radioactive and you can measure their activity find out the cross section for alpha n, alpha 2n, alpha 3n channels. So, this is how the offline experiments are done. And lastly many a times you know the physics community particularly they would not like to do offline measurement they want to do online measurements. They want to find out the cross section by online experiment. So, here I have tried to explain the online experiment. The online experiment you irradiate a target. So, I have shown a photograph of an experimental setup in electron at TIFR. We have this target ladder and a particular target you to suppose this is the target you are exposing to the beam and in the forward direction. So, beam will go out on this way. See there are these stainless steel cups you know there are two telescopes. Telescopes means delta EV telescopes you have a thin sapphire detector and you have a thick sapphire detector. The thin one will stop will reduce the energy of the charged particles like proton, alpha and so on. And the thick one will stop permanently. So, a two-dimensional plot of delta E and E the signal of this delta E and E will if you see if you recall the formula d by dx mz square by E the stopic power formula. So, D versus E is a hyperbola. D versus E will give you this hyperbola for different masses like proton, neutron, elem3, elem4 and so on. And you can put a gate on this bananas to get the energy spectra. You can sum the delta E plus E to get energy spectra. You can take the total area to get the total counts. So, whatever counts you get from these experiments these counts are related to n again n sigma phi instead of n sigma phi number of target atoms per centimeter square. Now, you are doing it at a particular angle. So, you do not have sigma, you have the d sigma by d omega that is called the differential cross section and this is the total charge total number of particles which you can measure on your faraday cup. So, you identify the different particles by delta E telescope this assembly as you have shown here and you generate the two-dimensional plots for different particles that are produced. So, it is the particle that are imitated in a nuclear reaction and then you can find out the energy spectra of these particles. You can integrate over the energy to get the total cross section. So, cross section for particle induced reaction by online mode will give you differential cross section at a particular angle and that you can then try to integrate to get the total cross section over the angle. So, that is the kind of experiments one does if you are doing online experiment you do in delta E telescope if you are doing offline you can do by measurement of activity of the radioactive procedures. So, this is how you can measure the cross section for charge particle induced reaction. So, I will stop here and the next lecture I will give the different type of reactions that take place that type of reaction mechanism in the next lecture. Thank you very much.


Hello. I'm Terry Fisher. This is the eighth of 12 lectures on copyright. In the preceding lecture, I examined two of the four major economic rights associated with a copyright, specifically the right to control reproduction and the right to control modifications of a copyrighted work. In this lecture, I'll examine the other two major economic rights, the right to control distribution and the right to control public performances and displays. As usual, I'll spend most of the time discussing the law in the United States, but we'll also indicate various issues on which the law in other countries differs. As always, I'll be illustrating the presentation with the various audio-visual materials, one of which is a map of copyright law, the current version of which can be found on my home page, tfisher.org. We'll begin with the right of distribution. This aspect of copyright law is characterized by a clash between two powerful sets of impulses. On one side are strong economic interests of copyright owners. On the other side is an equally powerful set of attitudes hostile to the copyright owners yearning for continuing control over embodiments of their works. The tension between these forces has generated and will continue to generate strife and periodic doctrinal eruptions. The interests of the copyright owners are, as I say, strong. For three reasons, they want to be able to control what purchasers and possessors of copies of their works do with those copies. The first and least important of those reasons is that such control supplements the copyright owners right of reproduction, specifically by enabling the owners to attack intermediaries who do not themselves make unauthorized copies, but who traffic in unauthorized copies. In this sense, the distribution right is analogous to the rules and criminal law penalizing the receipt of stolen property. The second and more important reason is that copyright owners would like to suppress, if possible, resales and lending of copies of their works. In other words, they would like to prevent the first purchaser of a copy from passing it on to others. Why? Because the result would be to increase demand for copies and, thus, to enhance the copyright owner's income. For example, novelists would like to be able to prevent sales of used copies of their books. Movie studios would like to prevent or to charge for resales or rentals of DVDs embodying their works and so forth. Third, copyright owners would like to prevent arbitrage, which corrodes their ability to engage in lucrative differential pricing. This last point is both complicated and important. I touched on it very briefly at the end of lecture number four. I now want to discuss it in more detail. The following analysis consists of a condensed version of an argument deployed in much more fine grain in an article I wrote some years ago on this topic. If you're curious about this phenomenon, you might wish to follow the links on my home page. Differential pricing, otherwise known as price discrimination, consists in the core case of charging different consumers different prices for access to the same good or service. A more subtle form of differential pricing involves charging different consumers different prices for different versions of the same good or service when the variation cannot be explained by differences in the costs of the versions. A familiar example of the core case of differential pricing is when a bus company or museum charges lower entrance fees to students or senior citizens than it does to middle-aged non-students. A familiar example of the more subtle form is the practice of airlines to charge vastly more for a business class seat than for a coach class seat for a given trip. Suppose, for example, that I want to fly from Boston to Los Angeles in the afternoon of June 1, 2014, roughly three months from right now. I prefer American Airlines, so I visit the website of the company and check for available flights and prices. Flight 143, which departs at 4.30 in the afternoon, suits my schedule well. I now have to choose a class. As you can see, there are various options, but the major choice involves where in the plane I will sit. Flight 143 uses the Boeing 757-200 aircraft, which is configured as follows. So if I want to sit in what's known as the main cabin, I will pay $400 or $500. If I want to sit up front in first class, I'll pay more than three times as much. The difference between these prices cannot be explained on the basis of the extra costs associated with a wide seat, better food, and more attentive service. Rather, it reflects primarily the airline's shrewd effort to capitalize on differences in the price sensitivity of the two types of passengers. If I'm wealthy or I'm able to rely on the generous business expense account, I'll choose first class. If neither, I'll choose the main cabin. Price discrimination usually increases the profits of the firm that engages in it. Why then is it relatively uncommon? Because with rare exceptions, the practice of price discrimination is feasible only when three conditions coincide. First, the firm ordinarily must have market power. In other words, there must exist no readily available equally satisfactory substitutes for the good or service the firm is selling. Otherwise, customers from whom the firm seeks to extract a high price will defect to competitors. Next, the firm must be able to differentiate among its customers on the basis of the values they place on the firm's product or service. There are several ways in which this could be achieved. In what economists refer to as first degree price discrimination, the firm gathers information about individual buyers and attempts to charge each one the most that he or she is able and willing to pay for the good or service in question. In so-called second degree price discrimination, the seller does not know how much buyers are able and willing to pay, but induces them to reveal their resources or their preferences through their purchasing decisions. Among the techniques of this sort are volume discounts and versioning, such as the practice I mentioned a minute ago of differentiating business class and coach tickets and then charging radically different prices for them. In so-called third degree price discrimination, the seller does not know the purchasing power of individual buyers, but is able to separate them into groups that correspond roughly to their wealth or eagerness. The student discounts and senior discounts I mentioned previously are examples. Opportunities to engage in first degree price discrimination have traditionally been rare, but opportunities for second and third degree discrimination abound. One area in which they're proliferating especially rapidly are the kinds of informational products to which copyright law applies. Take software, for example. One of the ways in which software firms seek to enhance their revenues is by selling identical or versioned copies of their products to students for vastly different prices than the prices they charge professionals. Here's an illustration. As you can see, as of today, February 23, 2014, Adobe's Creative Suite 6 is ordinarily priced at $1,700, but is available to students and teachers, groups that tend to be poorer than average, $4,590, a huge markdown. As I hope you recognize, this is an example of third degree price discrimination in which the copyright owner uses a criterion to separate the set of potential customers for its product into two or more subgroups, which differ roughly in their price sensitivity, and then charges the members of the two groups very different prices. An example of second degree price discrimination is the way in which book publishers typically package and release their products. In the usual case, a hardcover edition is sold at a substantial price, and then, a few months later or a few years later, a much cheaper paperback version is released. For example, right now I'm reading Scott Turow's novel Identical, the newest in a series of excellent legal thrillers. I bought a hardcover copy of this book about a month ago from Amazon.com for $28. I could have obtained from Amazon a paperback copy for a much lower price, but I would have had to wait until July of this year to get it. The cost of manufacturing a hardcover copy of a book is not double the cost of manufacturing a paperback copy. Rather, the sharp price difference is a form of differential pricing. More specifically, this common marketing practice, used by book publishers, combines two distinct price discrimination schemes. The first is known as versioning, just as was the case with respect to business class versus coach airline tickets. Publishers expect price insensitive consumers, like me, to buy the premium, in other words, hardcover editions, and poorer consumers to prefer the economy model. The second strategy is sometimes known as intertemporal price discrimination. The reason that publishers do not ordinarily release the paperback editions at the same time as the hardback editions is that they don't want buyers who care little about price but find paperbacks perfectly acceptable to opt for paperbacks. So they wait until the market, consisting of wealthy consumers, has been pretty well exhausted through sales of hardbacks before putting the cheaper versions on the shelves. The same composite strategy underlies the so-called windowing system through which most Hollywood movies, at least until recently, were marketed. Typically, a firm was first licensed for performances in American movie theaters. Roughly three months later, it was released both in foreign theaters and through pay-per-view channels. Three months after that, DVD copies were made available for sale and rental. After three more months, it was released to premium cable television channels. A year later, it was shown on television in countries outside the United States and then on network television inside the United States. Finally, after another three years, it was licensed to local television syndicators. The price per viewing paid by consumers in each of these windows was lower than in the preceding window. Again, we see here a combination of versioning, which prompts consumers to sort themselves by format and inter-temporal discrimination, whereby the most price-sensitive consumers have to wait the longest. There are many more examples of price discrimination by copyright owners, some of which we'll encounter later in the course. But there remains one more condition essential to this strategy. To engage in effective price discrimination, a copyright owner must be able to prevent, or at least to limit, arbitrage. In other words, must be able to stop customers to whom it sells copies of its work at a low price from reselling them, either directly or with the aid of intermediaries, to customers from whom the firm is seeking to extract a high price. If it can't do so, then the copyright owner forfeits its high-margin customers, which is disastrous. This is where the right to control distribution comes into play. What copyright owners would most like would be a legal right to prevent altogether any resales of copies of their works, not just for the reason we've already seen, namely that such a right would increase demand for their products, but also for the more subtle reason that it would enhance their capacity to charge different customers, different prices without worrying that poor customers who bought the copies for low prices would resell them to rich customers for intermediate prices and thus corrode the high-end market. To summarize, for three reasons, copyright owners would like strong rights to control distribution of copies of their works. First, it would help them to attack intermediaries who traffic in unauthorized copies. Second, it would enhance demand for copies of their works. And third, it would enhance their ability to engage in differential pricing. Opposed to these interests are not only the obvious economic interest of consumers in reducing the amount they have to pay for access to copyrighted works, but also three widely shared attitudes hostile to the kind of control the copyright owners seek. First, copyright owners who seek to prevent resales or lending of copies of their works are often seen as greedy. They've already been paid once when a copy of their works was first sold. They're not morally entitled to more. This sentiment is loosely tied to the principle of proportionality that figures so prominently, as we saw in lecture number two, in the fairness theory of copyright. Copyright owners is widely thought do not deserve to collect more revenue than they receive from the first sale of copies. Exactly why not is unclear, but this attitude is very common. Second, many people and many lawyers in particular are skeptical of attempts to control a thing after you have sold it. Viewing the same issue from the other side, a widely shared attitude is that once you have bought an object, you're entitled to do with it whatever you want. Among the manifestations of this sentiment in the law is the bias against restraints on alienation of real property, in other words, land. And the impediments I mentioned once before to servitudes, longstanding restrictions on what people who buy land can do on or with it. The same sentiment figures in the debate over the Monsanto case, which was decided last year by the United States Supreme Court, which concerned the right of a purchaser of seeds that contained genes, subject to patent protection, to grow crops from that seed, save some of the seeds produced by those crops, and then use the saved seed to grow more crops. The Monsanto case involved patent and contract law, not copyright law, so the complex legal issues at issue in that case are not pertinent to our subject here. But one of the general sentiments expressed often in the public debate over that case is that the farmer, Vernon Bowman, having bought the seed should be able to do what he wants with it. The same sentiment tilts against the interests of copyright owners to control redistribution of copies of their works. The third attitude is skepticism concerning differential pricing. Now, this attitude is not universal. Some forms of differential pricing, for example, the practice of US private universities of charging students very different tuitions depending on the financial resources of their families, are accepted without much grumpiness. But other forms, even trivial in amount, can provoke rage. Here's just one example. In the fall of 2000, amazon.com began to adjust the prices of a few DVDs depending on the status of the purchasers. It seems, although most Amazon representatives denied this, that repeat customers, identifiable by the Amazon cookies on their computers, were quoted higher prices for films than were new customers. Presumably, Amazon thought the new customers might shop around, and so offered them lower prices to induce them to buy. When this practice was revealed on an online DVD talk forum, the response of most participants was fury. Quote, I will never buy another thing from those guys, declared one consumer. Surveys confirm the prevalence of the sentiment that underlies this reaction. For example, in 2005, the Annenberg Center asked 1,500 adult internet users some questions concerning their views of online marketing practices. 87% disagreed with the proposition that, quote, it's OK if an online store I use charges different people different prices for the same products during the same hour, end quote. The way this attitude bears on our subject today is that, to the extent copyright owners seek increased control over the distribution of their works in order to more effectively engage in differential pricing, they face strong, though not universal, popular resistance. The tension between these competing forces has managed, to some degree, by a set of interlocking statutory provisions to which we'll now turn. The financial interests of copyright owners are protected by sections 1063 and 602A of the US statute. The first of these, as you can see, gives copyright owners the exclusive right, quote, to distribute copies or phono records of the copyrighted work to the public by sale or other transfer of ownership or by rental lease or lending, close quote. 602A gives copyright owners analogous rights to control importation and exportation of copies of their works. Now, if these were the only relevant statutory provisions, they would reflect total victory by the copyright owners. But each of these provisions is qualified by others. The right granted by 1063 is curtailed quite sharply by 109A, which, as you can see, provides that, quote, the owner of a particular copy or phono record lawfully made under this title, or any other person authorized by such owner, is entitled to sell or otherwise dispose of the possession of that copy or phono record, close quote. This provision is widely known as the first sale doctrine. The basic idea underlying that doctrine is that once a copyright owner has sold a copy, he cannot control resales, gifts, et cetera. We'll return to the precise meaning of this provision in a minute. The right to prevent unauthorized importation of copies is also qualified in various ways. Three specific exceptions are listed on your screen. In addition, the way in which 602A is phrased leaves open the possibility that it is qualified, not just by these specific exemptions, but also by the much broader first sale doctrine embodied in 109A. How might this work? Well, you'll notice that 602A refers to unauthorized importation as, quote, an infringement of the exclusive right to distribute copies under section 106, close quote. Section 106, in turn, makes all of the rights it grants to copyright owners, quote, subject to sections 107 through 122, close quote. Included in that list is 109A, which we've already seen. Through this chain of connections, it's possible that the first sale doctrine qualifies the importation right, as well as the right to control domestic distribution of copies of the work. We'll return to this textual nuance shortly. The first sale doctrine embodied in section 109A is itself subject to exceptions, specifically to the provisions of 109B1A. The key language is, quote, neither the owner of a particular phono record nor any person in possession of a particular copy of a computer program may, for the purposes of a direct or indirect commercial advantage, dispose of that phono record or computer program by rental, lease, or lending, close quote. The primary purpose of this provision was to shut down stores that, at the time of its adoption, were renting audio CDs to customers, would then copy the sound recordings on those CDs to the hard drives of their computers, return the CDs to the stores, and thereby avoid the cost of buying CDs of their own. As you can see, this exception is subject to exceptions of its own. So graphically, the relationship among these various provisions might be represented as follows. 106.3 and the primary portion of 602A advance the interest of copyright owners. 109A and 602A1 through 3 establish limits on those rights, giving expression to the sentiments opposed to the copyright owner's interests. 109B1A reinstates a portion of 106.3 with respect to some categories of works. 109B1B tempers that reinstatement. As I hope you can see from the diagram on your screen, this combination of statutory provisions seeks to manage the deep tension between the competing forces that shape this field of the law. But the statute is not precise enough to resolve all issues. The result is that there is lots of litigation along this fault line. I'll describe two sets of cases of this sort. Others are likely to come up in the discussions that accompany this lecture. The reason why the relationship between 109A and 602A is so important is that it determines the power of copyright owners to engage in international geographic price discrimination. In other words, to sell copies of their works at high prices to customers in the United States and at lower prices to customers in poorer countries. In lecture number three, I mentioned one among the many companies that engage in this practice, Omega Watch. Here's a brief reminder. Omega has obtained a US copyright on the design shown on your screen. Omega engraves a version of this logo on the underside of its watches. Omega sells those watches all over the world. Typically, it sells them for lower prices in poor countries than in the United States. Some years ago, Costco, a discount retailer using an intermediary, purchased some of the watches that Omega had sold cheaply outside the United States, imported them into the United States, and then began selling them in its US stores for prices lower than those used by Omega's authorized US dealers. Omega brought suit against Costco, contending that this so-called parallel importation violated Omega's copyright in the logo. Now, Costco had a seemingly strong defense. In an earlier case, called Quality King versus Lanza, the United States Supreme Court had held that 109A did indeed limit the reach of 602A, the result that a copyright owner could not block importation of copies that he or it had sold outside the United States. However, Quality King involved so-called round trip parallel importation. In other words, a situation in which the copies of the work in question were lawfully manufactured in the United States, shipped overseas, sold at low prices there, bought overseas by an arbitrageur, and then imported by the arbitrageur back into the United States, where they were sold for prices lower than those charged by authorized US dealers. Omega, relying on a concurring opinion by Justice Ginsburg in the Quality King case, pointed out that its situation was different. The watches that bore its copyrighted logo and thus the copies of the logos themselves were not first made in the United States. They were manufactured in Switzerland. As a result, Omega argued 109A did not bar its claim against Costco because 109A only applies, as you can see, to copies, quote, lawfully made under this title. The phrase, this title, refers to title 17 of the US Code, namely the US Copyright Statute. Omega argued that because the watches were not made in the US, they were not made under the US Statute, and thus the provision did not apply, and thus Omega had a right under 602 to block unauthorized importation of the watches bearing the logo into the United States. It's a clever argument, and it worked. The Court of Appeals from the Nice Circuit agreed with Omega, ruling that the first sale doctrine applies to copies manufactured outside the United States only if an authorized first sale occurs within the United States. Costco asked the Supreme Court to review the case, which it did, but the Supreme Court was unable to resolve the question. Four justices sided with Costco, four with Omega, and Justice Kagan recoups herself. The result is that the lower court's ruling stood. In other words, Omega won, but the main issue had not been definitively resolved. Last year, in the Kurtzang case, the Supreme Court was provided a second opportunity to address this issue. The essential facts of that case were straightforward. Supepp Kurtzang was born in Thailand but educated in the United States. In 2007, he was studying for a PhD in mathematics at UCLA. Like many students, he had discovered that copies of English-language textbooks could be purchased more cheaply abroad than in the United States. Kurtzang decided to capitalize on this fact in order to finance his graduate education. He asked his relatives in Thailand to buy their large quantities of textbooks of various sorts and ship them to him in California. He then resold the books to US students for prices below the rates that the publishers were charging in the United States, but well above the prices in Thailand. He was thus able to repay his relatives and keep a substantial amount of money for himself. This system enabled him, in short order, to earn roughly a million dollars, enough to finance his graduate education and then some. At this point, you're probably wondering, wasn't Kurtzang aware of the legal risk he was running? After all, the copies of the books he was importing bore clear warnings that his conduct was unlawful, like the warning shown on your screen. He might have thought that he, like many students, could avoid the wrath of the publishers if he operated on a small scale. But did he think that he could sell a million dollars of books with impunity? Apparently, yes. In making that judgment, he relied on advice from his relatives in Thailand and upon the website Google Answers, which assured him that he could legally resell the foreign editions in the United States. In the short term, Kurtzang's reliance on that advice proved foolish. One of the publishers, John Wiley, brought suit against him, contending that unauthorized importation of the books constituted copyright infringement. Because all of the books in question had been manufactured and first sold by Wiley's wholly owned subsidiary outside the United States, Wiley could indeed point to the omega decision for support. Wiley prevailed in the trial court and then the Second Circuit Court of Appeals. Kurtzang asked the Supreme Court to review the case, which agreed. The stakes were very high. Not just book publishers, but the sellers and buyers of all copyrighted materials distributed at different prices in different countries would be affected by the outcome. As one might imagine, the Supreme Court was deluged with briefs from organizations with stakes in one result or another. This legal battle was paralleled by a struggle for dominance in the so-called Court of Public Opinion. Here's one foray into that war, sponsored by the groups supporting Kurtzang. I think that once you've bought an item, you should be able to do with it what you want. If you want to resell it, that should be up to you. Because I paid money for it, and gosh dang it, I should be able to do whatever I want with it. I don't own anything. I'm just borrowing things from a company for a long time, which seems to be outrageous. How can they tell you that you don't own when you bought and you use your own money to buy that? I think that would be totally unfair against capitalism. I would say it would be important to everybody because that's just the way of America that we buy, we sell, we trade. Country boundaries aren't what they once were. So, of course, I mean, you should be able to buy and sell things regardless of where you get them from. Of course, of course, because most of the things I got on there are made from someplace else. I'd be very highly upset and pissed off due to the simple fact that they're trying to tell me what to do with an item. It'll affect everybody. You know, anybody that has a power to purchase now will be impacted by this. For one thing, in college books, it would be a killer. It's already so expensive to go to college that we should be able to use whatever textbooks we want, you know, wherever we got them, without having the threat of the government telling us that that's not appropriate to use. It really hurts the consumers on that site. I really could, I really concerned about the consumer because I'm a consumer. That seems to add a whole new level of administration. This is going to cost millions and millions of dollars. And that's just all that money going into having to ask someone if you want to sell your own things. That seems silly. What you would do, just thinking of kind of the gravity of what that would mean, it would piss me off a little bit. If I want to buy it, I'll buy it. If I want to sell it, I'll sell it. It's my right. Perhaps moved in part by sentiments like these. The Supreme Court, in the Kurtzang case, somewhat to my surprise, reversed the ruling of the lower court, holding that one-way parallel importation, like round-trip parallel importation, is privileged by section 109. The heart of the court's rationale was that the statutory phrase, quote, lawfully made under this title, quote, quote, is not a geographic limitation. So long as copies of a work are made with the authorization of the copyright holder, they are, and the Supreme Court's judgment, lawfully made under this title. The decision by the Supreme Court is widely and rightly regarded as a win for at least some consumers in the United States, whom, A, as a result of the ruling, be able to obtain copyrighted materials more cheaply. On the other hand, the decision disadvantages the residents of poor countries. The reason is that the sellers of copyrighted materials are likely in the future to find it somewhat harder to engage in international geographic price discrimination. If so, how will they respond? One option, of course, will be to reduce the prices of their goods in the United States. If their markets in poor countries are large enough, they may do that. But it's at least as likely that they will increase the prices of their goods in poor countries, thus, disadvantaging consumers there. So returning to our chart, the ruling in omega has now been superseded by the ruling in Kurtzang. The struggle over this issue is probably not finished. Copyright owners, most of whom are unhappy with this outcome, are already seeking to change the law, either through an amendment of the US Copyright Statute or through adoption of a treaty provision that would compel the United States and all other members of the treaty to amend the statute. Indeed, they are likely to seek not just to return to the omega rule, which would forbid unauthorized one-way parallel importation, but elimination or qualification of the earlier ruling in Quality King, which, as you'll recall, authorized round-trip parallel importation. Stay tuned. But for the time being, here's where the law stands. OK, that's one of the zones of ongoing litigation on this fault line. Here's another volcano. Autodesk makes CAD software, in other words, computer-aided design programs. Its main product is known as AutoCAD. It distributes AutoCAD in the old-fashioned way, namely on CD-ROMs. Just as we saw with Adobe, AutoCAD engages in explicit price discrimination. As you can see from this slide, it sells the program to commercial users, presumably architects, for very high prices. It then uses various techniques to sell the program to other groups, such as students, for much lower prices. One of those techniques is versioning. For example, as you can see from this slide, a student edition, presumably a detuned edition, of the program is available for less than 5% of the commercial version. Another technique that Autodesk employs to facilitate price discrimination is contract. In other words, the company seeks to impose upon customers various restrictions on what they're permitted to do with the copies of the programs they buy. In the 1990s, those restrictions included the following. First, Autodesk retains title to all copies. Second, Autodesk grants the customer a non-exclusive, non-transferable license to use the software. Third, the purchaser agrees to refrain from various activities, including reverse engineering the software or using it outside the Western Hemisphere. Fourth, the purchaser agrees to destroy copies of the software within 60 days of the time the purchaser upgrades it. Among other things, these restrictions sought to destroy the secondary market for copies of Autocat. In 1999, a company called CTA acquired through legitimate channels 10 copies of the 14th release of Autocat. Some months later, CTA paid a modest fee for an upgrade to obtain the 15th release of the program. But instead of destroying its copies of the 14th release, CTA sold them to a man named Werner, who, in turn, offered them for sale on eBay. Werner was a pure intermediary. He signed no contract with Autodesk and never installed or used the software. His only ambition was to resell the copies at a profit. Autodesk got wind of this plan and sought to block the eBay sales on the ground that they would violate Autodesk's exclusive right under 1063 to distribute copies of the program. Werner contended that the sales in question were privileged under 109A. So here's how the competing parties told their stories and described their legal implications. Werner conceded that Autodesk had a valid copyright in Autocat. Exercising its exclusive right under 1061 to reproduce the software, Autodesk made a copy on a CD-ROM. Exercising its exclusive right under 1063 to distribute that copy, Autodesk then sold it to CTA. CTA then exercised its privilege under 109A to resell the validly acquired copy to Werner, who similarly relied on 109A when seeking to resell the copy through eBay to another buyer. As Werner told the tale, every step in this process, including the last one, was lawful. Autodesk, not surprisingly, saw things differently. Steps one and two were just as Werner described them. But instead of selling the copy to CTA, Autodesk contended that it merely leased the copy to CTA in return for various promises. CTA then purported to sell to Werner a copy it did not own. Because 109A only applies to, quote, the owner of a particular copy, close quote, it did not shield this transaction. The purported resale thus violated Autodesk distribution rights under 1063. For the same reason, this last transaction was not shielded by 109A. Werner was no more an owner of the copy than with CTA. Thus, selling the copy on eBay also violated 1063. In sum, according to Autodesk, both this transaction and this one were unlawful. The key issue in the case thus became whether the relationship between Autodesk and CTA had been a lease or a sale. Werner, of course, preferred the latter, Autodesk, the former. In 2010, the Court of Appeals for the Ninth Circuit ruled in Autodesk's favor. Here's the decisive portion of the court's opinion. We hold today that a software user is a licensee rather than an owner of a copy where the copyright owner, one, specifies that the user is granted a license, two, significantly restricts the user's ability to transfer the software, and three, imposes notable use restrictions. The way in which this decision fits into the overall landscape of the law governing distribution rights is indicated on the map. It's reasonably well settled that, using Nimmer's typology, a transaction involving a copy of a copyrighted work is covered by 109A and thus a lawful, if and only if four conditions are satisfied. A, the copy was lawfully manufactured with the authorization of the copyright owner. B, the copy was transferred under the copyright owner's authority. C, the defendant qualifies as the lawful owner of that particular copy. And D, the defendant thereupon disposed of that particular copy, as opposed to, for example, reproducing it. When software firms provide customers copies of their programs in return for money, requirements A and B are more or less automatically satisfied. However, if the software firm adds to the transaction enough conditions to make the deal appear to be a lease of the copy, and thus not a sale, then requirement C is not satisfied. And as a result, the customer does not have a privilege to resell that copy. This option is highly beneficial to software firms for two reasons. First, by suppressing resales of copies, it enables the firms to sell more original copies. Second, it helps the firm suppress arbitrage of copies sold cheaply to students and so forth, and thus protects the firm's primary markets, consisting of adult or commercial users. The result, as you might expect, makes the software firms happy, but makes their customers much less happy. Again, a highly technical ruling, which locates this particular transaction on one side rather than the other of the fault line, has large economic implications. This concludes our analysis of the rights of distribution. After the break, we'll turn to the even more intricate set of rules governing public performances.


A formal eviction happens when a landlord orders a tenant to leave their home, either because that tenant missed rent payments or due to other infractions and the landlord files an eviction filing. In court, a tenant is called into court and a judge rules on whether or not that tenant will be evicted. We estimate that across the country about 2.7 million eviction filings happen each year through the courts. I emphasize through the courts because we also suspect that for every one formal eviction or an eviction that goes through the courts, there are about two informal evictions. So evictions that happen without a court order. Maybe a landlord tells a tenant that they're going to evict them and the tenant gets out before having a scarlet E on their record or a landlord shuts off the utilities or one of many, many different ways in which tenants are forced to leave their homes without the court actually getting involved.