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Tutorial #5

Activity 10- RadiationBiological Effects of Radiation Exposure

Ikjyot Singh Kohli

1Sunday, 22 January, 12


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What is Radiation?

Radiation -> Many different interpretations/

contexts/meanings, we are concerned withhere, the type of radiation that CAN BEHARMFUL!

Radiation -> We are concerned then withIonization Radiation



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Ionization RadiationParticles that can remove an

electron from atom ormolecule.

Removal Process --> Known asIonization



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Physics Point of ViewVS. Biology Point of View

What energy is this? - X-rays, GammaRays, alpha particles, beta particles,

etc...5Sunday, 22 January, 12


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Atom withmissing

electron, i.e,.

unpairedelectrons, isnow a Free

Radical



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4 Types of Radiation



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Gamma RadiationUnits of Radiation:

Typically measured as effect of radiation on livingtissue --> Amount of energy deposited, called the

Absorbed Dose

Gray (Gy) (J/kg) -> SI Unit of absorbed dose,amount of energy required to deposit 1 J in 1 kg

Biologists: Use the equivalent dose, biological effectof radiation on human tissue, for Gamma rays =Absorbed Dose (Units of Sieverts (Sv = Gy) for

Gamma Rays)8Sunday, 22 January, 12


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Sources of Gamma Rays

One possible source -> Already seen throughradioactive decay, but other sources possibletoo.

Most Interesting of these are Gamma RayBursts



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Artist's illustration showing the life of a massive star as nuclear fusion converts

lighter elements into heavier ones. When fusion no longer generates enough

pressure to counteract gravity, the star rapidly collapses to form a black hole.

Theoretically, energy may be released during the collapse along the axis of

rotation to form a long duration gamma-ray burst.

http://en.wikipedia.org/wiki/Gamma-ray_bursthttp://en.wikipedia.org/wiki/Gamma-ray_bursthttp://en.wikipedia.org/wiki/Gamma-ray_bursthttp://en.wikipedia.org/wiki/Black_holehttp://en.wikipedia.org/wiki/Black_holehttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/Massive_starhttp://en.wikipedia.org/wiki/Massive_star


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Drawing of a massive star collapsing to form a black hole. Energy released as

jets along the axis of rotation forms a gamma ray burst that lasts from a fewmilliseconds to minutes. Such an event within several thousand light years of

Earth could disrupt the biosphere by wiping out half of the ozone layer, creating

nitrogen dioxide and potentially cause a mass extinction.



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Gamma Rays in thenews!!!



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Health Effects

Gamma radiation is the most penetratingtype of radiation, hence, have the mostserious health implications, specifically,

RADIATION SICKNESS.



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Gamma Ray Radiation -

Positive Uses (!)

Kill bacteria, used to sterilize medicalequipment

Used to kill some cancer cells

Also used for security, because ofpenetration ability



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Gamma Ray Positive

Uses

Also used for security, because of penetration ability



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The Experiment

Design an experiment to test the following

hypothesis:

Seeds Exposed to an excessive amount

of radiation yield abnormal plants



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The Experiment

Attempt to grow some radish plants with theseeds provided with your kits.

A period of at least 4 weeks will be

required to grow your plants, so, plan

accordingly!!

Specific step-by-step instructions are onPage 93 of your workbooks, read these verycarefully!!



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What to Hand In?Page 1

Describe Your Experiment and YourFindings

Statement of the hypothesis beingtested

Description of your experiment you

designed to test the hypothesis

Summary of your observations

Conclusions



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Page 2 - Detailed Drawing of your experimentalsetup. It should be carefully labeled

Page 3 - ORIGINAL Log sheets and any supporting

materials (drawings/photographs)

Note: Log Sheets are your experiment diaries,

EVERYTHING MUST BE WRITTEN ON THEM,

including the time you wrote them, and thedate. NOT ABOUT NEATNESS, BUT DETAIL!!



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Important Tips

-Pots containing the normal and irradiated seedshave to be labelledclearly to avoid confusing themwith each other (since, once they are out of theirrespective bags, the seeds look identical).

-Conditions in both pots must be kept the same asmuch as possible, which means soil, initial placementof seeds, lighting, watering, temperature, and so on.



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Part IIPopulation Growth Issues



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Population Growth

Concepts of population growth rest heavily

on the notion ofExponential Growth.

Review of Exponential Functions



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PopulationsAssume you have a population that over timehas the following sequence:

5000, 13591, 36945, 100428, 272991,...,110,132,329

Take any 2 numbers, and take their

ratio: 100428/36945 = 2.7182e = 2.71828183 = Eulers number

Exponential Function: y = e^x27Sunday, 22 January, 12


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Exponential Function



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Practical Uses



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Exponential Chaos

Exponentialdivergence

oftrajectories



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Mandelbrot Set



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Julia Set



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Expansion of the Early

Universe35Sunday, 22 January, 12


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Interpretation of

Population Data

Suppose you are given the following set ofdata for two countries:



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Calculate the rates of natural increase

of Country A and Country B37Sunday, 22 January, 12

RNI =


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RNI =(Crude birth rate Crude death rate)

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Developing Countries:Positive or high RNI

Developed Countries:Negative/Neutral or Low RNI

Caveat: Still increasing due to rise inimmigration!!


RNI =


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RNI =(Crude birth rate Crude death rate)

10

Country A: RNI = (43-18)/10 = 2.5Country B: RNI = (8-10)/10 = -0.2

Clearly B is the developed countryA is the developing country

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