in the last episode we talked about how we can use proton beams to analyze ancient artifacts and gather data about uh where or when this ancient artifact was made uh based on cross referencing the data that we have gathered from it to historical data that is available to us uh and we're following up on the same concept of ancient artifact anal sis and preservation in this episode, but this time using gamma rays and instead of using uh historical data using math, so so that's why we've come here to dr. sohrapur building, who is one of the original founders of the irradiation application research school uh to find out how we can take advantage of gamma race to gather more data about the age of an artifact and how we can preserve it for future generation, so that's what we're going to be covering in this episode of iran tech, with me your host aliza, stay tuned.

let's start by talking about preservation. uh, preservation against what exactly? well, preservation against organic material, that is to say, microorganisms that exists within of the the dirt. or even the air, these microorganisms, mainly consisting of a fungy and bacteria, can damage our artifact in many different ways, for example, let's say we have ancient painting and it consists of lot of different substances, so we have the piece of cloth that is the canvas and that can be torn as a result of disintegration of the particles within that piece of cloth because of the microorganisms, because they use the substances within, uh the uh the artifact as

nutritional material to live and to cultivate themselves, it can also damage and discolor the paint on this painting uh again because they can use the paint as some sort of um supplement for themselves and the wood can also be become brittle and fragile because of the disintegration of the bonds, the chemical bonds between the particles of the wood uh, but there is... a weakness that these microorganisms have that we can exploit in order to preserve these ancient artifacts from them and that is the fact that all microorganisms, all living things in fact, have lot of water within them, but before we get into that too much, let's uh take a step back and uh get a closer look at some of the different types of damages that these microorganisms can uh affect uh the artifacts and then talk about the different ways that

we can directly or indirectly uh preserve our artifact against these microorganisms. since historical artifacts are mainly made out of organic compounds, over time they get exposed to biological changes. the living microorganisms on the surface of these historical artifacts will decay them. the microorganism destruction, which is mainly due to bacterian fungi, includes consuming the surface of organic compounds to grow and reproduce. as a result of this reproduction,

the number of these microorganisms increase dramatically on the surface of these art effects, as well as this, it leads to the destruction of surface layers. in addition to that, the extracellular organic compounds secrete acids and enzymes that change the color of surface organic compounds or decompose them. in order to increase the... activity of historical artifacts, one of the protection methods is using disinfection methods such as gammaray, gammaray affects microorganisms into two different ways, mainly its indirect effect composes the microorganism's environment, which is mainly made up of water, then it releases free radicals with high kinetic energy, these high... kinetic energy free radicals attack of

constituent molecules of microorganisms and decay them. the gamma rays directly affect the genetic materials of microorganism cells and decay and decompose them into different pieces. if microorganisms can successfully repair the damages in their genetic materials, they can regain their normal life. otherwise they will be decayed. one important thing which should be considered in historical artifacts iradiation is the inadverent impact of irradiation of surface materials. if surface materials can ender irradiation, we will have a certain dosage of irradiation. in fact, we choose two dosage ranges, minimum and maximum dosages. we use that range to irradiate historical artifacts.

this way we increase the longevity of historical artifacts. our primary goal is to keep these artifacts safe and sound and pass them. down to the next generations. okay, so we now know that if the gamma rays don't directly damage or kill the cells outright, because while the cell has level of resistance to gammories, and even in case of damage it can repair itself uh in some cases to an extent, then we need to take advantage the water molecules surrounding this cell uh and uh use the... gamma rays and the effect that it has on the water molecules to affect the cell indirectly, but in order to understand how the gamma rays, what happens a molecular level when the gamma race hit the water molecules and how they affect the genetics of the cell, we need to take a really closer look. the energy that the gamma

rays carry thanks to gamma ray's high penetration power, gets to all microorganisms in on our artifact and damages the dna of said microorganisms. which include various types of bacteria, fungy, spores and others that can damage or disintegrate ancient artifact over time. the reason why gamma rays can damage biological molecules with high effectiveness is because of the fact that gamma rays are of the ionizing type of radiation. when the rays hit the dna of a cell, they can directly ionize the dna molecules, which leads to the dna helix breaking. if these pears are not repaired by the cell can lead to various problems with cell function and can lead to its eventual death. the amount of the gamma irradiation must be controlled however, as too much radiation can degrate not just the microorganisms, but the artifact itself. so

it is crucial to have thorough understanding of what said artifact is made up of and control the amount of radiation that are source, in this case cobalt 60 is emitting. while destroying the microorganisms with gamma rays, we have also managed to preserve it to a degree from future microbial, or otherwise infections, by sterilizing the artifact and riding it of chemicals that microorganisms need to feed off off to survive. this method is particularly great for fragile artifacts or those that are prone to tears on contact. it is also environmentally clean and residue free. there's no reason not to use it. well, less the dosage is right? so that's how we use gammarays to uh preserve ancient artifacts and now let's talk about how we use gammarays to uh date ancient artifacts uh that is to say uh which not only which uh era in history

they belong to, but also their actual age. so in the previous episode we talked about the vandday graph machine and how we used a proton beam to date ancient artifacts, but we don't actually date the artifacts, only say which era in history that artifact belongs to based on the type of elements, the type of material that we have found in our sample, so that's how we would date using that method, so we would cross reference the kind of material that we have found in our sample to when that kind of material was used the most in history, but with this method, the electroluminescence, the thermoluminescence method uh we can actually determine the exact, rather exact age, uh of our uh artifact uh so and that works uh with uh the kind of radiations that our ancient artifact absorbs throughout time, so in order to understand what i mean by thermoluminescence, we need to take a closer look at the basics of thermoluminescence and the science behind

it, so let's do that now. in order to use thermoluminescence dating method for historical samples, we need to determine two factors: the first one is the equivalent dose the sample, has received throughout the years buried in its place, and the second one is the average annual dose rate existing in the sample's place. the radiations affecting our sample might be cosmic radiation or the radioactive radiation. existing in the soil around the sample, in order to determine the age and equivalent dose, we have got to prepare very small amount of our sample, implementing proper techniques and provide certain types of crystal out of the sample, all in all, we only need one gram of the historical sample. after determining the proper size of the samples, we irradiate the sample using various dosages of gamma and better rate, the result will be calibration curve for that sample, in order to determine zero. age, we must extrapolate the adator of this curve and gain the first dose that our

sample has received to determine the average annual dose rate existing in the samples place. the commercial dose emitters of thermoluminants with high sensitivity must be taken to the closest possible depth of the sample. they can be placed there for quite a long time. the environmental radiation will leave its influence on them and then they will be taken to our laboratory. again, their thermoluminance radiation is measured there eventually after thermoluminance radiation measurements and also determining the density of radioactive material in the samples bural place and other required data, using our software we can estimate the age of our ancient sample with the approximation of few decades. the principle in thermoluminescent stating is that certain mineral crystals trap electrons. with their structure as they are exposed to radiation, particularly galactic radiation that accumulates over time and is

absorbed to different degrees at different depths of the earth, but we are mainly concerned with artifacts that are made up of certain mineral crystals like ceramic or some types of rock, especially ones that have come into contact with fire, like pottery or bricks, as the fire had zeroed all thermoluminescence properties that the substance might have accu. estimulated over time and makes it a lot easier to date, but to zero in on the thermoluminescence itself, and what it entils, we need have an atomic scale look. in crystals, there are imperfections and defects that extend to the orbital structure of electrons and as radiation is absorbed by the crystal, electrons can become trapped in these defects instead of just moving up in orbit as they gain energy. think of these defects as how. off orbits that the electrons are trapped in, but as you heat up the artifact and the

electrons gain some energy, they can break free from their trap and get back down to their original position, their original orbit if you will, and the process, some energy is released in the form of photons that are detected and based on their energy level, we can use it to date our sample, the thermo refers to the heating of our sample for the electrons to gain energy and the luminescence. first to the light that is emitted as a result of the electrons releasing energy as they come back to their original place in orbit. so to recap, this is the equation that we need to uh calculate if we want to get to the number uh which is the... age of our ancient artifact, and on the top of this fraction we have the equivalent dose, which is the total

amount of radiation that our sample has absorbed throughout its life, so since it was made up until the point we discovered it in the ground. at the bottom we have dose rate, which is average of the dosage that any sample would absorb over a certain period of time, based on the data that we have collected from the docimeters that we have planted in the ground. at the depth that we found our sample in, and uh, when you simplify this fraction, what you're left with is a unit of time. now this time is usually uh in years, and this is how you can actually calculate the age of a particular uh ancient artifact sample, and uh that was going to be it, so um, this this is how we determine the age of sample, and we also showed you how we use gammarays uh to preserve ancient artifacts and that concludes our two... episode series on how to analyze ancient artifacts and also how to preserve them. hope

you've enjoyed it and i'll see you in the next episode. bismillahirrahman. ولقد كتبنا في الزبور من بعد الذكر ان الارض يرثها عبادي الصالحون. ان في هذا لبلاغا لقوم عابدين. وما ارسلنا لاك الا

رحمه للعالمين، قل انما يوحي الي انما الهكم اله واحد، فهل انتم مسلمون. صدق الله.

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