biyofizige giris

7/28/2019 Biyofizige Giris

1/21

Physics:a science which investigates thenature.

Creatures that compose the natureare divided into

two main groups:

1) the livings (alive)2) the non-livings (not alive

PHYSICS investigates non-livings.

BIOPHYSICS deals with the livings.

Because alive creatures have a dynamicstructure,topics of biophysics are more complicatedthan those of physics.

Basic positive sciencessuch as mathematics and physicsalways include definite information.

e.g.

2 + 2 = 4F = m.a (Newtons Second Law)

Engineering,where mathematics and physics comeacoss in application,is also positive in character

MEDICINE ?

Also one of positive sciences...Definitely positive ???Unfortunately, not.

Medical information rather relays onobservations and experiments,not definite as 100%.

It is an art as well as science.

Sometimes, a patient may be lostdue to a simple mistake made by a doctor.e.g. Anestesiology faults during anoperation.

Descartes, a French Philoshopher, hadsaid to his patients:

I am trying to establish a medicine basedon mathematics and physics. Take care ofyourself, well till that time.

At this point,

the importance of Biophysics appears:

Biophysics aims to explain

biological and medical events

in accordance with the rules ofmathematics and physics.

From the second half of twentieth century,

science and technology,especially electrical engineering andelectronics, developed very fast.

Electronics and computers are now widelyused in medical applications.e.g. Ultrasonography, MRI (MagneticResonance Imaging), CT (ComputedTomography).

With the use of these medical imagingtechnics, objective scientific data instead

of doctors subjective comments areapplied in modern medicine.

To learn Biophysics is necessary

for better understanding of clinicalsciences

such asneurology,neurosurgery,cardiology,cardiovascular surgery,orthopedics,anesthesiology,physical medicine and rehabilitation

On the other hand,a multidisciplinary co-ordination between

biophysics and clinical sciences isessential

for effective usage of modern medicaltools.

1.Sunum Introduction to Bio h sics


2/21

Introduction to Biological andMedical Physics

Physical Measurements

Unit Standards

Biomechanics

Biomaterials

Bioelectronics

BioopticsBioacustics

Systematic of the Creatures

Bioenergenitcs

Laser Beams and their Use in Medicine

Infrared Beams and their Use inMedicine

Biological Effects of ElectromagneticFields

Biophysics of The Respiratory SystemBiophysics of The Vascular System

Biophysics of The NeurologicalSystem

Scientific Basis of Pain

Scientific Basis of Pain Management

Neurostimulation

Neuroimplantation

Acupuncture Technics

Biofeedback

Scaler Measurement

Meaningful with number and unit, only.

e.g.1 kg sugar, 500 g tomatoe (mass),3 m2 carpet (surface),50 m3 wood, 2 lt milk (volume),4 h, 5 min, 10 s (time),18 C 300 K tem erature .

3.Sunum Biomechanics


3/21

Physical Measurement

A concept that is necessary forphysical evaluation of measurementsrelated to creatures in the nature.

Scaler Quantities Vectorel Quantities

Vectorel Measurement

To describe some quantities,

number and unit are not enough;

other specifications have to bedetermined.

e.g.

Wheat in a land.Its starting point where it locates on earth,its direction depending on win,its lineand its lenghtmust be known for a complete description

This example shows that

a vectorel measurement necessitatesthe determination of four parameters:

- starting point (application point),- line- direction,- amplitude

Physical quantities such as

force,speed,acceleration,moment,impulsecan only be explained with vectors

If the lines of certain vectors are inparallel, and their directions andamplitudes are the same, then thesevectors will be called as equalvectors.

If the lines and amplitudes of certainvectors are the same, but theirdirections are opposite, then thesevectors will be called as

opposite vectors

Components of a Vector

In two dimension co-ordinate system;

i and j: unit vectors

V = Vx i + Vy j

V = Vx2 + Vy2

Vx = VCosVy = VSin

In three dimension co-ordinate system;


4/21

Addition of VectorsTotal vectoris a vector that is equal toaddition of more than one vector.Addition of vectors which areon the same line and in the samedirection;

Addition of vectors which areon the same plane and in thedifferent direction;

Addition of vectors which areon the same line and in the opposite direction;

Total of the opposite vectors is equal to zero

Problem 1Lenght of a vector is 7.3 unit and it makes250 with the positive horizontal axis in thedirection of counter clockwise. Find thecomponents of this vector.Solution:

A = 7,3 birim

= 250Ax = A Cos = 7,3 Cos 70 = -2,5 unitAy = A Sin = 7,3 Sin 70 = -6,9 unit;

Problem 2Horizontal component of a vector is 25

unit, and its vertical component is 40 unit.Find amplitude and angel made with thehorizontal axis of this vector.Solution:

A = Ax2 + Ay2 = (25)2 + (40)2 = 47,1

tg = 25/40 ===> = arc tg 25/40 = 32 = 32 + 90 = 122

Problem 4

The bistoury of a surgeon goes to east by3 cm first, then to north by 4 cm startingfrom a point, S. Calculate the totaltransposition (replacement) of the bistouryregarding to starting point, S.


5/21

UNIT STANDARDSAfter all,some countries still insist on to use theirtraditional units.e.g. England.So, sometimes, it may be necessary toconvert the units each other:

1 = 2,54 cm1 pound = 454 g1 mile = 1609 m1 feet = 0,3 m

1 galon = 231 inch3

Force:

effectthat changes

shapeormovement

of thematter.


6/21

There are, therefore, two kinds of effect offorce on the matter:

Effect on the shape of matter,deformation;

deformative effect is less on solidmatters than that of elastic ones.

e.g. iron, tennis ball, cotton.

Effect on the movement style of matter,acceleration effect; speeding up.braking effect; slowing or stopping.

Gravitation

effect pulling all matters down to center ofthe earth.

The reason for such a force is not clear.Any how, it has been suggested thatgravitation results from anelectromagnetic wave due to movement ofinternal layer of the earth.

Gravitation is not the same everywhere;it is the lowest in equator, and the highestin the celestial.

Mass and WeightMass and WeightGravitation depends on the location of the matter on theearth.Gravitation that effects a matter at the point where it islocatedon the earth is called as itsweightweight.

G = m . g

G: weightm: mass

g: gravitation accelaration (9.81 m/s2)

e.g.e.g.

Weight of a matter of which mass is 1 kg is;in equator: 9,78 N,in Ankara: 9,79 N,in the celecitals: 9,81 N,in moon: 1,6 N.

Newtons Lawsthree laws explain relation between force and

movement.

Newtons First Law Newtons Second Law Newtons Third Law

Newtons First LawNewtons First LawUnless a force does not effect on a matter,

no acceleration will occur.

if it is standing it will continue to stand, andif it is moving (linear movement with at aconstant speed)

it will go on to move in the same way.

The first Newtons law explain

Newtons Second LawA force effecting on a matter is proportionalwith acceleration resulting from this force.

F = m . awhere;

F: forcem: mass (proportionality constant)a: acceleration

In this equation; force and acceleration arevectorel measurement, but mass is scaler.

Special circumstance;F = 0 ====> a = 0

which has the same meaning with the firstNewtons law.Newtons second law explain the concept of

Newtons Third LawNewtons Third LawIf a matter apply a force to another matter, thatmatter also applies a force with the same intensityin opposite direction.

effect = reactioneffect = reaction

The first Newtons law explainthe concept ofinertia or inactivity.

First and second laws of Newton are related toforce affectin a matter whereas Newtons third


7/21

Units of ForceUnits of Force F = m . a

in CGS standards;

[dyne] = [g] [cm/s2]in MKS standards;

[N] = [kg][m/s2]

Since

Center of MassA solid matter can be considered as a

composition of differential pieces.

differential piece: the smallest piece we can

imagine.

Gravitation affecting each differential piececan be thought as forces in parallel.Combining force of these forces are called asweightiness of that matter, and its applicationpoint as center of gravitation or center of mass.

If there is more than one force effectingon the matter, combining of these forcesbehaves like a force in the center of mass.

Combining of the forces effecting on thematter crossing over the center of massmakes the matter move to change itslocation.

EnergyEnergyability of the matter to do work.ability of the matter to do work.

There are two sorts of energyThere are two sorts of energy

Energy Protection PrincipleEnergy Protection PrincipleEnergy cannot be created from the

absence, and present energy cannot be

made absent.

In a closed system; sum of the potentialand kinetic energy is constant:

Ep + Ek = constant

Closed system is a system that isindependant of outside medium.

Universe is also a closed system.

VelocityVelocity

Force, acceleration, lenght andvelocity are all related concepts. When aforce is applied to a matter; according to

first and second Newtons laws, thatmatter will accelerate, and take lenghtwith a velocity.

Velocity, that is a vectoral quantity,is first derivation of lenght to time.

v = dl/dtunits; [m/s] = [m]/[s] m/s; cm/s; km/h

AccelerationAcceleration

Acceleration is also a vectoral quantity.It is first derivation of velocity to time, or issecond derivation of lenght to time:

dv d dl d2l

a = ----- = ----- [-----] = ------

dt dt dl dt2

units;

m/s2 or cm/s2


8/21

MomentMomentMoment is the rotating effect of force. M = F ^ d

Moment of same directional parallel forces;Moment of same directional parallel forces;

According to moment saving principle,total moment is equal to zero; M = 0

F1.a + F2.b = 0

F1.a = - F2.b

Effect and Reaction Forces in HumanEffect and Reaction Forces in HumanBodyBody

According to Newtons third law,an effecting force is balanced bya reverse reaction force with the sameamplitude.

Also the human body,depending on the gravity acceleration,is affected by the gravity force, andthere is an opposite directional reactionforce with the same amplitudeto keep the position of body in balance.

e.g.e.g.

A 80 kg person who is standing up,where the gravity acceleration is 9.8

m/s2 ,will be under the effect of gravity of:

G = m.g = 80 kg . 9,8 m/s2 = 784 N

and there is an opposite reaction force of784 N.

Effective Forces in Physical TherapyEffective Forces in Physical Therapythe forces effecting on the patient duringphysical therapy;

Muscle force,Force applied by the physiotherapist,Gravity,

Friction force of the ground.


9/21

Problem 3What is the distance a laser beam pulse can take

in an hour in miles (velocity of light beam in

space = 3x1011 m/s, 1 mile = 1609 m)?Solution:

v = l/t

l = v.t = 3x1011 m/s .1x60x60 s = 10800x1011mSince,

1 mile = 1609 mthen,

10800x1011 / 1609 = 6,712x1011 mile

Body Mass Index

m (mass) [kg]BMI = ------- ---------- ---------

h2 (height)2 [m]2

Problem:

Calculate body mass index (BMI) of a manwhose height is 1.70 m and mass 60 kg?

Solution: m 60 kg

BMI = ------- = ------------- = 20,7 kg/m2

h2 (1.70 m)2

BMI < 18.5 kg/m2 low weightedlow weighted

18.5 kg/m2 < BMI < 25 kg/m2 normalnormalweightedweighted

25 kg/m2 < BMI < 30 kg/m2 overoverweightedweighted

30 kg/m2 < BMI < 40 kg/m2 obesobes

BMI > 40 kg/m2 morbid obesmorbid obes >> lifethreatining

The force has two types of effect on theThe force has two types of effect on thesubstances:substances:

changing the form of the substance(deformative effect),

effecting the manner of the movement(accelerative or decelerative effect).

In this section, to specify the biomaterialswe are going to examine the deformative effectdeformative effectof the forceof the force:Solide substancesSolide substances; These are the substancesthat are accepted free from the deformativeeffect of the external forces.Elastic substancesElastic substances; These are the substancesthat can be deformed by the effect of an externalforce, but they return their initial form when theforce exerting on them is removed.Plastic substancesPlastic substances; These are the substancesthat can be deformed by the effect of an externalforce, and they cannot get back to their initialform when the force exerting on them is removed


10/21

Actually,

the atoms and molecules

which form a substancechange their initial position in a smallnumber when facing to an external force;

but during these position disturbance insolids, atomic linkages do not break downas they are very powerful..

In solids,

normally, the distance between atoms is

approximately equal to 0,2 nm,

and it should alter to 0,0002 nmunder the influence of an external force;

it means that the deviation is only 1/1000.

Thats wh

ElastomersElastomers

Elastomers are substances withweak interractions (links) between atoms.

e.g.e.g. Caoutchuc and rubber.Some rubber can elongate and reach

10-15folds of its original lenght.Whenelastomers are heated, their resistance

towards elongation increases.

In soft (loose ) ( e.g. alveolar) tissues,the elasticit is rovided b 10 m in

Hooke LawHooke LawHooke Law indicates the rule of elongationevent.

Experimental data shows thatquantity of elasticity is proportional with theforce exerting on the object.

F l+F/-x = tg = k: constant ===> F = - k.x

Youngs ModuleYoungs ModuleAccording to the Hooke Law; the elongation inlenght is proportional with the force applied onthe object, and this situation is given by F lNow, going through the pressure concept whichis determined as the force exertingon an unit surface,

F l---- = Y.-----A l

can be written.

Y: the Youngs module which is a coefficientrelated to the ender of the substance.

Pulling and compressing compulsions of anobject can be different. For exemple; this is thecase for bone.

Youngs modules of some substances:Youngs modules of some substances:

Substance Youngs module

Bone 9x109

N/m2

-16x109 N/m2

Steel 200x109 N/m2

Wood 3x109 N/m2

Rubber 0,003x109 N/m2

Poisson LawPoisson LawAs a substance elongates in lenght,it compresses from height and width.Relative altering ratios in height, width andlenght:

h w l------ = ------ = - ------

h w l

here; : poisson ratio: poisson ratio

Volumetric Deformation (Compression)Volumetric Deformation (Compression)The volume of an objectunder the pressureis applied in every direction changes. Thischange in volume, V

P = B -------V

In this statement;

P: Pressure,B: Compression elasticity module,V/V: Volumetric deformation.


11/21

Elasticity of biological substancesElasticity of biological substances

The structure of heterogen quality biologic

materialsis rather complex.

As most of the biological processes dependon water,biological substances are generally found inwatery mediums(71% or 3/4 of human body is water).

Beside,

solid and rigid biological substances like

tooth, there are semi-rigid(solid) biologicalsubstances like bone and cartillage tissues.

Bone is made of collagen fibers andhydroxiapatit (Ca+PO4) crystals.

Implantable Devices

Passive implants

No operation in the body, mechanical

support, only

e.g. Ortopedic implants, dental

implants

Active Implants

Operational in the body

e.g. Cardiac pacemakers,

neuroimplants

Active Implantable Devices

Semi-implantableFully implantable

Implantable Materials

Temporarily implantablePermanently implantable

Body Compitable Metals (medical grade )

Silver ??? (maybe applied in animalstudies, only)Gold ??? (not advised, because ofrheumatic prob.)Platinum (platinum irridium)TantalumTitaniumStainless-steel (316L)

Dental Implants

Silver ??? (just in history)Gold ??? (just in history)PorcelaineTitanium

Medical Grade Titanium(Grade 4)

SheetWireRodPowder

Implantable FormsCases (implant housing)Wires (electrodes)

Sheets (contacts)

Other Body Compitable Materials(medical grade)

SiliconesPolyurethaneTeflonBioceramicsBioglassMedical adhesivesMedical markers


12/21

Quality Assurance of Implants

FDA (essential in USA)CE (essential in Europe)ISO 13485ISO 9001

Electrical Activity as a Sign of LifeAll of the livings have an ongoingelectrical activity along their life.

They are electrically active as long as theyare alive.

Therefore,the presence ofelectrical activityin a livingcreature indicates the presence of life on it.

Each creature, even a simple one, is amiracle.

Human, within all kind of creatures, hasbeen equiped with the best anatomicalconstruction and physiological function.

The human body may be resembeled toan extraordinarialy good electronic devicewhich of any similar thing is not possible tobe made.

All kinds of engineering systems such aselectrical, electronics, mechanical, otomaticcontrol, statics, thermodynamics, robotics, etc.exist and work perfectly in human body.

In order to survive such a transactionhappens in the body which connot be simulatedin industry.

Thanks to feed-back controlling systems

which are more excellent than the most excelentone,a lot of systems like digestive, muscular,nervous, bone, respiratory and vascular systemswork harmoniously in human body.

All of these systems carry out life functions,

but the nervous system is of specialimportance.

It has the task of coordination within all othersystems.

In other words, it is the administrator one.

5.Sunum Bioelectronics

The sensory systemThe sensory system helps us defendourselves from the surrounding hazards.

In addition to this, autonomic nervousautonomic nervous

systemsystem is responsible for working ofsome very important organs like heart,stomach, liver, kidney, ect.

All these activities are controlled byelectrical activity in nervous system.

In actual fact,there is electrical activity in every single cell,

but speciality of the cells of nervous systemneurons - is to conduct their electricalsignal to neighboring cells under certainconditions.


13/21

Anatomically speaking;Anatomically speaking;the brain and spinal cord form

central nervous system.

Peripheral nerves come out of the spinal

cord asthirtyone pairs just like branches of a tree,

andthey spread all over the body.

Physiologically speaking;Physiologically speaking;

bare nerve endings,namely receptorsreceptors, located very close to

skin,

work just like energy transformers transducerstransducers in technology.

.

When a receptor percept any kind ofphysical stimulant (touching, warm-cold,seeing, hearing, tasting),

it is first of all converted into miniatureelectrical signals,

e.g.e.g. in case of touching,mechanical energy is converted intoelectrical energy.

Nerve impulses, formed this way, areconducted to the spinal cord by peripheralnerves.

Within the nervous system, there are contactpoints, namely synapsesynapse, where two neurons getin touch.

At the entrance of the spinal cord, the firstsynaptic contact happens; soon after thatanother synapse occurs;the part of nerve between these two synapses iscalled interneuroninterneuron.

By means of interneuron, nerve impulses passacross the cord, thus the second transmissionway starts, and goes up to the thalamusthalamus where anew synapse is created to form the thirdtransmission way for the impulses to reache thesensor cortex.

Nerve impulses carrying various sensationsis called action potentialsaction potentials, a kind ofbiopotentialsbiopotentials.

Brain demodulates action potentialsarriving in the sensory cortex by evaluatingthe patterns of the signals, and recogniseswhat the sense is.

In medical applications, for the purpose ofdiognosis, some devices in order to recordbiopotentials have been developed.

For instance; in order to record electrical activityof heart ECG (electrocardiography)ECG (electrocardiography) is used,for electrical activity of muscle EMGEMG(electromyography)(electromyography),for electrical activity of brain EEGEEG(electroancephelography).(electroancephelography).

All these devices, operating like an osiloskopdisplay bioactive signals on the screen or it giveprint outs.

During recording, if the patient is alive, these

devices show very small potentials as a sign oflife.When patient dies, a straight line will be shownon the zero axis.

The Effects of Electrical Current onThe Effects of Electrical Current onHuman BodyHuman Body

1- Thermic effect:burning of the body because of

excessive current,

2- Chemical effect:degeneration of the nervous system,

3- Shock effect:stopping of heart by excessive

current.

Impedance of the Cell, Tissue and SkinImpedance of the Cell, Tissue and Skin

On the cellular basis,

e.g.e.g. in neurons,the different chemical concentrations ofions inside and outside the cell causes apotential difference across the membrane,inside of the cell being more negative thanthe outside,because these ions have electrical charges.


14/21

Because the blood and other body fluids arein motion, the impedence of the living tissueis variable.

It is not a fixed value,changes according to time and place.

The values differ from person to person,in different parts of the same body,even in the same part of the same body atdifferent times.

Different Effects of Direct and AlternatingCurrents

Both direct and alternating current will beharmful when they flow through the body over

safety limits, but the degree of effect is differentto type of current.We know that impedance of the living tissue is

frequency dependant, because of its capacitivefuture.

We also know that electrical conductivity isproportional to the frequency for the samereason. XC =1/C=1/2fC

iC = V / XC = V / 1/C = V / 1/2fC = 2fC.V

As seen from the equations of capacitivereactance and current, when the frequencyincreases current increases, and

In case of direct current (D.C.);f = 0 then iC = 0

in fact, the cell, tissue and skin has twocomponents of current:resistive component and capacitivecomponent. i = iR + iCduring D.C.;

i = iR

In case of alternating current (A.C.);depending on f, there is also capacitive

current.

f iThis mathematical analysis shows that A.C.compared with D.C. with the sameamplitude is more effective in harming the

living tissue.e.g. 42 V A.C. can cause the same effectwith 70V D.C.

In labsIn labs during experiments foreducational purposes;

42 V A.C. and 70V D.C. arelegally allowed current limitslegally allowed current limits..

In networks that connected to theground;

safe touching voltagesafe touching voltage is accepted as 65VA.C. by the Ministry of Energy.

The impedence of dry skin is between 100k and 600 k,but in wet skin this value falls down to 1k,thus the impedence decreases between 100and 600 folds.

Thats why parents warn their children not totouch the electrical ligth switches and plugsockets with wet hands.

Problem:How much current passes through a personwho touches the electrical network systemby wet hands? Comment on the result of thisaccident?

Solution:

I = V / Z = 220 V / 1000 = 0.22 A = 220mATo answer the second part of the question,we must look at the table of safe anddangerous current values.

As seen from the table of safe anddangerous current values,

electrical current of 220 mA, passing througha person who touches the electrical network

by wet hands,kills the person involved in this accident.

As seen from the example given,electrical current can cause a fatal effect onhuman body.

So, one may ask a question thatwhy do we use electricity and take such a risk,then?

Wouldnt be better not to use electricity?

Electricity is, certainly, one of the best productsof technology, and we need to use it at homes, inoffices, in industry, in medicine and other fields.

Even if we only think about the importance oflight,without electricity the life would reflect a MiddleAge life style vision.We need electricity, and we must use it, safely,in accordance with technical rules.Otherwise we can face with results which areunrecoverable.

The electricity pruduced in a power station is firstraised to 380 kV that is very high voltage by araiser transformator, andit is then given to the national network.

When energy arrives in a main distributioncenter, it is lowered to 166 kV or 66 kV that ishigh voltage.

In the distribution centers in cities, the voltage is

lowered to 34,5 kV or 15 kV that isintermediate voltage.

Whatever it is finally lowered to 0.4 kV by a laststep transformer located in certain places in thedistricts.That is the voltage of energy coming to ourhouses or work places.


15/21

After substraction of the line loses which is

5%, we have the standart voltage of380 kVthat is called interphasal voltage.0,4 kV = 400 V

400 V x 0.05 = 20 V400 V - 20 V = 380 V

The phase neutr voltage is 220 volt.There is a 3 coefficeint beetwen thesevoltages:

U: interphasal voltageV: phase-neutr voltageU = 3 . V380 V = 3 x 220 V

We know that65 V A.C. is accepted as safe touchingvoltage by the Ministry of Energy.

So one question may come to minds;

why do we still insist on using 220/380 Vnetwork system in cities since it is sodangerous?

To prepare the answer to this question,technical and economical aspects must beconsidered.

P: power (W)l: distance (m)

k: selfconductivity (m/-mm2)q: cross section of the energy transmission line

(mm2)U: interphasal voltage (V)

V: phase-neutr voltage (V)Line Looses;Line Looses;P.l

%u = ---------------- in 1-phase systemk.q.U

P.l

%v = --------------- in 3-phase systemk.q.V


16/21

These formulas for calculating line lossesreveal that thick wires should be usedto decrease the looses.

In long distances, this is impossiblefor both technical and economical reasons.

So,very high (380 kV) and high voltages (166 kV or66 kV) are to be used in the national network,intermediate voltages (34.5 kV or 15 kV)in intercity distribution system,

and low voltages (220/380 V) in houses andworking places.

Factors Which Increase the Risk ofFactors Which Increase the Risk ofElectrical AccidentElectrical Accident

Broken instruments and tools, Useage of materials which are out of

standard, Wrong electrical connections todevices, Excessive current, Wrong temporary electricalapplications, Humidity, Incom atible network volta e.

Precautions Against Electric AccidentsPrecautions Against Electric Accidents

Handling and repair of electrical equipment,Control and check,Inter-vocational trainning of personnelagainst electric accidents,Allowing of only licenced technicalpersonnel to use electric instruments,Application of standard fuses andother protective circuit elements,Application of complete and appropriategrounding.

Electrical Security SystemsElectrical Security Systems

Grounding SystemsGrounding Systems

In the places where electricity is used,

connection of condutive metallic parts togroundis called grounding.

Electrical current prefers a pathway withsmaller resistance to flow.

Curent always follows short circuit.

Because a short circuit has the lowestresistance, zero.

These are major rules of electricalengineering.

There are three types of grounding:There are three types of grounding:

1) Protection grounding,

2) Operational grounding (related to TEAand TEDA),

3) Special grounding (not our concern).

Protection GroundingProtection GroundingProtection grounding is applied to send escapedcurrent, resulting from a breakdown in thesystem, to the ground, for protecting people whotouch metallic parts of a machine on which there

is no current in normal operational conditions.

Grounding of the metallic parts of machines thatwork with electricity, electrical devices, metallicparts of transformers, seconder windings ofmeasurement transformers, steel armour ofunderground cables, and bodies of steelbuildings are


17/21

Grounding EquipmentsGrounding Equipments

Grounding Plates and Pipes,Grounding Conductors,Grounding Pools.

Grounding Plates and PipesGrounding Plates and PipesUsually copper plates or galvanized steel platesare used as grounding plates.

According to the relevant regulating rules;the copper plates must be minimum 2 mm inthickness and must have a surface of 0.5 m.

In order to provide this surface area, there are 70cm70 cm copper plates available in markets.

On the other hand galvanized steel plates mustbe minimum 3 mm thickness and 0.5 m surface

Grounding ConductorsGrounding ConductorsThe grounding line which connects the groundingplate to the main energy enterance of thebuilding should be bare, full copper wire with 50mm.

The same type of wire which is of minimum 16mm should be used between the main energydistribution panel and the energy enterance ofthe building.

The grounding line between the main panel andthe subpanels should be half of the phaseconductor in thickness not being less than 4mm.

Inside the building, 2.5 mm grounding line issuitable for the plugs.

Grounding PitsGrounding Pits

A humid place which can take rain continously issuitable for a grounding pit.The pool should be at least 1.5 m in deep.

If the soil is dry, the deep of the hole may beincreased in order to reach a humid soil.The grounding plate should be put into the holewith a right angle andthe upper end of the plate should be 50 cmbelow the surface of the soil.If the soil which has been digged is not clear, itshould be sievedbefore it is used for stuffing.The surface of the grounding pool should bearranged in a pool like shape in order to makethe rain water accumulate there.The soil which is ressed b knockin on after

6.Sunum Radiation Bio h sics

A nucleus is formed by two components:protons and neutrons.

Protons are positively charged,

and they have a unit load (+ 1).

Neutrons are neutral.

Protons and neutrons, forming the nucleus,are together called nucleon.

Neutrons exist in nuclei that have 2 or moreprotons.

The number of protons may be same with thenumber of neutrons.

If the number of proton is equal or close to thenumber of neutron,

this atom is said to be in stable state.

If the number of proton is less or more than thenumber of neutron,the atom is in unstable form, and it tries to passthe resolute state.

For this purpose, the destruction or deteriorationoccurs in nucleus and spreads radiation.


18/21

Problem:What is the reason for 137 Cesium to beradioactive (its atomic number is 55)?

137 M = 137Cs A = P = 55

55 M = P + N

137 = 55 + N

N = 137 - 55 = 82

N >>> P Thats why 137 Cesium is

Atoms can be in two different forms:

Stable Form(Stable Atoms)

PN ~ NN

Unstable Form(Unstable Atoms)(Radioactive Atom) (Radioisotope)

PN > veya < NN

These group of atoms try to pass tostable form, and to achieve this, they emit

Studies by Ernest RUTHERTFORT (1898)showed thaturanium emited two kinds of radiation:

(alfa) and (beta),

and this way it could be converted intoanother elements.

Later on,it was understood that

a (alfa) radiation was similar to 42He nucleus,and

b (beta) radiation looked like e-

.

The mass of b particule is the same with that ofelectron,and its charge is 1.

If the sign of b particule is negative, it will becalled electron,

If it is positive (+), it will be called positron.

Until 1912,30 more radioactive elements were found.These elements,

some of which were natural,some others artificial,

were called as radioisotopes.

First radioactivity tests on the livingswere undertaken on frogsfrogs.When the frogs, which were drunk

radioiodineradioiodine,placed on photograph films includingcarbon, it was observed that the films

got darken,after removing the upper skin, even moredarken.

There is not an exact rule to determine ifan isotope is radioactive or not.After all, there are some experimental dataabout the criteria of radioactivity:Atoms with nucleus having double number

of electrons are, generally, in steady state.The ratio of number of neutrons and protonsin nucleus give an idea about theradioactivity.The partition criteria for a nucleus:

45 < A2/M < 53,5

Experimental studies, employing naturalradioactive series, revealed that most ofelements with atomic numberbetween 81 and 92 are radioisotopes.The reason for this;The strong Coulomb repelling effect betweenprotons of elements with high atomic number

makes these elements unstable.To decrease the effect of Coulomb repelling,the nucleus undergoes a action, and thus itlosses 2 protons and 2 neutrons.Sometimes, the nucleus emits b beam. .

During this procedure; 1 neutron is converted

into 1 e+ and 1 e-.


19/21

When neutron and proton numbers isrepresened by a graphic,elements composed of stable atoms fall intosteady state region.

Radioactive elements, of which the ratio ofnumber of neutrons and protons are less orgreater than 1, are out of steady state region.

A few isotopes within stable state region are stillradioactive.

How a radioactive element will reach to thestable statedepends onthe ratio of number of neutrons and protons,and how close it to a stable element.A nucleus that is out of stable state regioncan emiteither or particule to reach to stablestate.

But, there is not a certain rule to reachstable state region.

e.g.e.g.The nucleus of torium 233, which isexpected to emit , prefers activity.

Atoms can be in two different forms:

Stable Form(Stable Atoms)

PN ~ NN

Unstable Form(Unstable Atoms)(Radioactive Atom) (Radioisotope)

PN > veya < NN

These group of atoms try to pass tostable form, and to achieve this, they emit

A t o m i c B o m bA t o m i c B o m bThe explosion of atomic bomb based on

the principle that combine specific amount of

radioactive elements(236U or233Th) which iscalled critical mass.Critical mass of uranium is estimated to be

mcritic

@ 2,6 kg

When the atomic bomb is explosed temperature

will be 4x106oK


20/21

The remaining product resulting from fusionreaction is much less than those fromfission.

For this reason, fusion reaction is a potentialcandidate as an alternative energy sourcein the future.

H y d r o g e n B o m bH y d r o g e n B o m bThe heat which is necessary for makinghydrogen bomb that is a kind of fusion reactionis provided from explosion of atomic bomb.

The amount of nuclear waste remainingfrom fusion reaction is much less than thosefrom fission; thats why hydrogen bomb hasbeen calledclean bomb.

The reaction in a nuclear powerstation is basedupon the disintegration of substances bypartition.Generally uranium 236 is used as a substance.The equation of reaction that is a fission reaction;236U 92Kr + 144Ba + enerjiParaphine wall prevents the radiation to escapethe environment.Because water, pumped through the waterchannels, involves in radioactivity,

it is not directly used; instead the vapor, takenfrom another water depot,results in movement of the turbine.

This mechanical energy is then converted intoelectrical energy by alternatorsThe Law of Radioactive Decay

Partition of radioactive nucleuses is arandom process;it cannot be exactly known which one will bedivided and when.But, it can be talked about the probability ofdisintegration.

: Partition constant (probability ofdisintegration per unit time).e.g.e.g.

I-131 = 10-6 s-1

This means thatonly 1 out of 1000000 radioactive iode atomnucleus will be divided in 1 s.

If in t time interval only N number of radioactiveatom is broken into pieces from N number ofradioactive atom,

N / t = - N can be written.In this equation,

(-) sign shows that the number of radioactive

atoms decreases in time.By integration; N = N0.e-t

N0:the number of radioactive atoms at the beginning

N: the number of radioactive atoms by the end of timete: 2.718 (base of natural logarithme)

DF = N/N0 = e-t: Decay Factor(% how many left from the atoms at the eginning)

A fission (partition)reaction.

Problem:The number of atoms of a radioactive material is10000, and partition constant 0.05. Find thenumber of atoms being divided and theremainings by the end of first, second and thirdsecond.Solution:after1 s; 0.05x10000 = 500 (divided)

10000 - 500 = 9500 (the rest)after 2 s; 0.05x9500 = 475 (divided)9500 - 475 = 9025 (the rest)

after 3 s; 0.05x9025 = 451.25 (divided)9025 451.25 = 8573.75 (the rest)

Physical Half Life

Time that is necessary for the number ofradioactive atoms to decrease down to half of itsoriginal value at the beginning. t = t1/2

N = N0/2By taking natural logarithm;

t1/2 = 0,693/Physical half-life is inversily proportional

to partition constant.As partition constant increases physical

half-life gets shorten.Decay constant is independant from

chemical and physical conditions (pressure,temperature, light).So, radioactive decay cannot be stopped, slowedor accelerated.By the end of physical half-lie, half of theradioactive atoms get lost, then half of the rest,and thus; in consistent with the equation

n

Decay CurveDecay CurveDecay curve which is a curve that shows changeof decay factor according to time on a halflogaritmic graphic paper.At the beginning (t=0)100 % decay factor (DF) ismarked (1st point). At the time of physical half-life 50 % DF is marked (2nd point).The line connecting these two points determinesdecay curve.


21/21

biyofizige giris

Documents