in the last episode we talked about how we can use proton beams to analyze ancient artifacts and gather data about 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 analysis 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. sorapur building, was 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 irontech 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 the the dirt or even the air. 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 the uh the artifact as nutritional material to live and to cultivate themselves. it can also damage and disc color the paint on this painting uh again because they can use the paint as some sort of 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't 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. production, the number of these microorganisms increase dramatically on the surface of these artifacts, 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 longevity of historical artifacts. facts, one

of the protection methods is using disinfection methods such as gammaray. gamma ray 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 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 ir radiation is the inadvent impact of irradiation of surface materials. if surface. materials can inder radiation, we will have a certain dosage of irradiation, in fact we choose two dosage ranges, minimum and maximum dosages. we use that range to radiate 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 generation. okay, so we now know that if the gamma rays don't directly damage or kill the cells outright, because well the cell has level of resistance to gammas and even in case of damage it can

repair itself uh in some cases to an extent, then we need to take advantage of 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 gammates 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 gammaray'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 our 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 tears 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 set 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 of 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, unless the dosage is right. so uh 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 vandigraph machine and how we used a proton beam to date ancient artifacts but we don't actually date the artifacts we 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 uh, 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 artif. so and that works with 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 thermoluminance dating method for historical samples, we need to determine two factors: the first one is the equivalent dose of the sample which has received throughout the years buried in its place, and the second one is the average annual dose rate existing in the samples place. the radiations affecting our sample might be cosmic radiation or the radioactive radiations 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 samples, we irradiate the sample using various dosages of gamma and beta rates, the result will be calibration curve for that sample, in order to determine zer we must traplate the data 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 dosimeters of thermoluminescence 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 environment irradiation will leave its influence on them and then they will be taken to our laboratory again. radiation is measured there eventually after thermoluminance radiation measurements and

also determining the density of radioactive material in the sample's 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 and thermoluminant stating is that certain mineral crystals trap electrons with their structure as they are exposed. 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 accumulated over time and make it lot easier to date, but to zero in on the thermoluminescence itself, in what it entils,

when 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 half orbits that the electrons 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, in 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 refers 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 you 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.

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