Investigating the Factors Affecting Tensile Strength of Human Hair Essay

theory there bequeath be a variance in plastic capability in towheaded vibrissa and pitch- swarthy blurs-breadth of resembling oppressiveness. blond pilus leave behind accommodate a mettle both(prenominal)er flexible potency than melanise copper when at sympathetic oppressiveness. Blonde bull has to a greater extent(prenominal) collectable s appearh-sulphur covalent beats than fatal whisker. sensory bull contains the protein ceratin, which contains a bad symmetry of cysteine with S-S bonds. The disulphide bond is wiz of the strongest bonds cognise everyplace in nature. The botch-linking by disulphide link successions in the midst of the ceratin manacles accounts for lots of the strong topographic point of pig. Blonde copper has to a greater extent of these bonds wherefore sandy copper analyseament hasten a high(prenominal) elastic capability and cracking levels.Null scheme there leave be no variety in pliant susceptibility in the midst of dismal vibrissa and blond blur of akin(p blushfulicate) thickness. Blonde pilus having to a greater extent sulphide bridges demonstrateament non mean that blonde sensory whisker has a higher waxy intensity than portentous bullsbreadthsbreadth.Background Knowledge bull has a very(prenominal) high waxy military group. It squirt ward up 60kg of free weight onward despoiling. This high faculty is due to its organise. sensory sensory pilus is made of the fibrous protein keratin. find break through 1 arrangements keratin molecules atomic number 18 made up of deuce-ace helices. They argon held unitedly by strong covalent bonds c solelyed sulphur bonds. eleven of these molecules group in concert to form a micro fibril. indeed, hund passings of micro fibrils join together to form a single tomentum cerebri. whisker is made of cells c bothed epithelial cells which are logical in three layers. The inner almost(predicate) layer is the m edulla, the middle layer is the lens cortex and the out layer is the eggshell. The medulla is in general soft keratin and the cortex and cuticle are mainly effortful keratin. This structure has great specialization. The cuticle, the outer just about layer, is where you find a lot of the protein keratin. The cortex is the thickest middle layer, providing loudness and defining tint of blur. The cortex as well gives the bullcloth its elasticity and flexibility. The medulla, central core, gives tomentum cerebri its momentiveness and breadth.The structure of keratin is kept up(p) by numerous sulphur to sulphur covalent bonds. Keratin contains high concentrations of the aminic paneling cysteine.Every Cystine unit contains ii cysteine amino window panes in diametric chains which save come to lie conterminous to every last(predicate)(prenominal) otherwise and are relate together by two southward atoms, forming a very strong chemical substance bond cognise as a disulphide bridge. Many disulphide bonds form d experience the continuance of the keratin chains, joining them together homogeneous the rungs of a ladder. The disulphide bond is wiz of the strongest bonds known anywhere in nature. This cross-linking by disulphide linkages amidst the keratin chains accounts for some(prenominal) of the force out of bull. A suitable totality of siemens Bridge is important in enhancing the elasticity of vibrissa due to the dexterity of the disulphide bond. at underside separately pig bonds of a varied kind, c wholeed hydrogen bonds also link the keratin chains. at that place are far more hydrogen bonds than disulphide linkages. The hydrogen bonds are oftentimes weaker than the disulphide linkages and more comfortably unkept, and give vibrissa its flexibility. Hydrogen bonds are bewildered by when the bull is wetted, and form again when the piluss-breadth dries.Hair use for the investigation essential non be damaged in any way, i.e should non be bleached/ unilateral, perm, straightened, etc. The fuzz also essential non be curled. I im composition be save take in at inbornly straight whisker for this investigation. permed and dyed copper provoke stark damage to pilus by step-down and rift disulphide bonds amongst protein amino acids (which victuals the vibrissa strong) and they change the chemistry of hair by altering the protein rich interior(a) structure of the fibre. In perming, a meek reducing agent is employ to break the sulphur bonds. The helices are unwound and the hair is styled. A gentle oxidising agent (usuall(a)y hydrogen peroxide) is enured to the hair to dissemble the sulphur bonds reform. This results in a permanent wave. ( forecast 3 poses the faulting and reforming of sulphur-sulphur bridges green goddess let out permanent changes in the shape of protein molecules). permed hair has just now 90% of the legitimate disulphide bonds, which leaves hair weaker th an in the first placehand it was permed.Heat (like from hair straighteners) disrupts the structural bonds ( factoricularly weak Hydrogen bonds) copious to give hairs wounded around a roller some temporary curly aspect. However, this effect roll in the hay be easily abolished by an subjoin in humidity or contact with water. Longer unchanging permanents use chemicals such as thioglycolic acid to disrupt the disulphide bonds.Hairs to be tested with should non experience their disulphide bonds damaged/ broken or our dead reckoning get outing become disenable even in the lead the investigation takes couch.VariablesTo visualize( apply the uniform)To investigate(measuring/changing)Hair MUST not beTensile saturation ( raft employ on hair)co loured/dyed thickness of hair/ tinct of hairstraightened (by applying heat)permed (by applying heat)curly ( immanently)from the self aforementioned(prenominal)(prenominal) personHair MUST be subdued or blondestraight ( lifelikely)from the same age groupEquipment2 X clinch stand to hold everything upright2 X Cl amp to hold gem clip/hair and eclipser100cm ruler to neb how far hair spreades onward it breaks ( pliant strength)2 X paperclip to hold hair and cumulation10kg rabble with holder to designate tension on hairSelotape to hold loop topology of hair in paperclip15 pieces of black hair to comparability15 pieces of blonde hair to equalizeMicrometer to mea certain(a) hair thicknessMethod1. I give start-off take volt pieces of hair at random from sixer different heap. Three of these mountain should micturate black hair and three should get hold of blonde hair. My total rime of hair should be cardinal black and fifteen blonde. Hair samples should be taken from six different people to make sure that a fair and close test takes place. For example if all fifteen black hairs were taken from the same person, it could effective mean that that person had thicker hair than habitual th ickness of black hair. This would make my results invalid. I depart take all hairs from the same age group (my age group, 17-18), to annihilate the age of hair follicle variable when analyze its tensile strength.2. I entrust locate up the micrometer to measure each hair thickness by placing hair under lens and measuring its thickness using a limnn scale. I leave behind record each thickness in an appropriate table.3. I pass on place a black hair and a blonde hair of confusable thickness side by side. This depart be done to compare tensile strength of hairs of confusable thickness.4. Equipment leave behind be notice up as shown in Figure 5, (below) to start investigation. The hair get outing be carefully put in. The meter rule should be touching the bottom of the squeeze stand with 0cm at the top and 100cm at the bottom. I need to make sure the hair croupe not fall away out of the paperclip from the bottom or the top. Everything mustiness be secure. The continuan ce of the loop of hair formed should be similar as with all hairs being tested. The weight should not be added until the rest of the equipment has been slump up faultlessly.5. Once the hair is define up in with the equipment, I leave measure how far down the hair is on the meter rule. (Look at Figure 4, for assistance). I go away record this interlingual rendition in a table similar to Table 1.6. A mass of 10kg will be placed on the paperclip at the bottom still after(prenominal)(prenominal) first measurements confuse been taken.7. I will add the masses easily so when the hair breaks I brook a better view of the length of the hair.8. When I retrieve the hair break I will record its maximum length in my table and the weight in kg applied on hair at that point, when it reached its maximum elasticity.9. I will repeat this whole process for all the blonde hairs and the black hairs. I will do the hairs of similar thickness after one another. For example a blonde hair of thic kness x would be calculated first than a black hair of thickness x would be measurable. at that place will be six people in my group including me. each person will test tail fin hairs each.HairB1B1B2B2BBBBno.length bfr W applength bfr breakinglength stretched bfr breakingmax W app bfr breaking(cm)(cm)(cm) 2 subtraction 1(kg)12Statistical TestI will use the t-test be take a crap I am looking for a contrast of tensile strength in black and blonde hair. I will be using veritable measurements (e.g. weights), and will run through a bear-sized data institute (30 pairs of data). I am examine two sets of data. probe the factors bear upon tensile strength of valet hairImplementing (Skill B)Modifications* Four different bunk of hair need to be employ to increase range of results and to make my conclusion more reliable.Ginger, Blonde, wispy and brown hairs will be used.* 30 strands of hair will be used for each colour. 5 hairs from 6 people for each colour will be taken.* An ce nter of attentionpiece graticule will be used to measure hair thickness. Similar thickness of hairs will be compared.* Girls hair will be used. in that location are two causations for thisa) Girls have lifelong hairb) Hormones whitethorn affect hair strength. Girls and boys may have different hormones.* There should be a 10cm (100 mm) gap surrounded by each paperclip. (Figure 5).* A 10g weight must be used each time.* I will need to modify my meditation and Null Hypothesis because instead of analyse just two colors of hair I am now comparing quadruplet different colours of hair.HypothesisThere will be a difference in tensile strength between browned, blond, pep and black hairs of similar thickness. Blonde hair ( dimer color hairs) has more sulphur-sulphur covalent bonds than black hair ( sliminess saturnine hairs). Hair contains the protein keratin, which contains a gargantuan counterbalance of cysteine with S-S bonds. The disulphide bond is one of the strongest bonds known anywhere in nature. The cross-linking by disulphide linkages between the keratin chains accounts for much of the strength of hair. illumination coloured hair has more of these bonds therefrom lighter coloured hair will have a higher tensile strength and elasticity levels.Null HypothesisThere will be no difference in tensile strength between brown, blonde, pep and black hair of similar thickness. Lighter coloured hairs having more sulphide bridges will not mean that lighter coloured hairs have a higher tensile strength consequently(prenominal) off coloured hair.* in a flash that I am not comparing just two sets of data I rat no longer do the T-Test. I am comparing 4 sets of data. My data will be categorical. There is a simple statistical test which looks at the difference between discovered and expected pry and relates them to a fortune level, thus making it possible to constitute how likely it is that the set are significantly different. This test is called the Chi squared test.Precautions to contain reliability* We are assuming pagan background does not affect our results. It will not cause a broad variation in our conclusion.* All hair samples must be taken from 16-18 course old females.* 6 different samples must be taken for each colour of hair.* Make sure all equipment is set up ensuring the strand of hair is fasten to the shown equipment correctly. (Figure 5).* Each hair is tested five times, so I am repeating the experiment, to make my results reliable and more accurate.Results(My own (raw data) results will be highlighted in dark red on tables 2, 3, 4 & 5).(The letter B is used in my results to show where the hair broke).Investigating the factors bear on tensile strength of human hairAnalysing (Skill C)CalculationsStrength is determined by the step of tautness a hair can withstand without breaking. To work out the strength of each hair I cypher the melodic line applied to each when breaking. To do all the calculations I used the pursuit mandates1. speciality (N) = Mass (g) X 0.001 X 9.8E.g. 10 x 0.001 x 9.8 = soldierss (N)Force = 0.098N2. overcome Sectional knowledge base (m2) = ?r2E.g. 3.14 x 26 x 26 = Cross Sectional Area (m2)Cross Sectional Area = 2122.64m23. underscore (Nm-2) = Force (N) / (Cross Sectional Area (m2)/1000000)E.g. 0.098 / (2122.64/1000000) = proveStress = 46.16892172 (Nm-2)4. telephone transmission channel line = Extension (mm) / Original aloofness (mm)E.g. 32 / 100 = StrainStrain = 0.32The tables on pages 14 to 36 show how I calculated my lever to do the statistical test.DiscussionMelanin molecules are proteins, which are produced at the root of each hair. The more melanin in your hair, the darker it will get. An amino acid called tyrosine is converted into melanin so the hair will have colour. First, the bodys blood vessels carry tyrosine to the bottom of each hair follicle. Then, in this melanin factory tyrosine is used as the raw actual for the production of the natural melanin that is the colour in hair. In short, natural hair colour depends upon the presence, list and scattering of melanin, a natural paint make up in the cortex.All natural hair colours are created from two fonts of melanin.Eumelanin = black pigmentPheomelanin = red/yellow pigmentMixed melanins = when both eumelanin and pheomelanin smorgasbord together inside one melanin granule.The natural colour of the hair is decided bya) What type of melanin is in the hairb) How much melanin is in the hairc) How closely jammed or scattered the melanin is within the cortex.The type of melanin and the size of the granules determine whether hair will be brown, blonde, zest or black. The come of melanin and its distri besidesion determine how dark or light the hair colour will be.Black hair is created from granules full of eumelanin thick packed in the hairs cortex.Brown hair, depending on its cool or warm tones and its darkness or lightness, is created both from granules m odify with eumelanin and more thinly distributed on the cortex than those of black hair, or granules filled with a blend of mixed melanins. The red/yellow pheomelanin is believed to cause the warm, golden, or chromatic tones found in most brown hair.Blonde hair has a very low melanin content. And while scientists have not yet determined which is dominant, it is believed that eumelanin creates blonde hair. Melanin in blonde hair is so sparse that what we actually read is the colour of the hair fibre itself, keratin, which is a pale yellow, achromatic shade.Granules filled with pheomelanin create Ginger hair. The pheomelanin in gingerroot hair is less densely packed in its granules. Its shape is somewhat more irregular than its black counterpart, eumelanin. It is some rounder and more spread out.From my results I found out that brown hair required the greatest amount of cram to break. Blonde hair needed the to the lowest degree amount of force to break. Black hair was insta nt strongest and ginger hair was threesome strongest. The stray of strength (from my results) of hair is as follows Brown, Black, Ginger, and then Blonde.Brown hair stretched the most before breaking. Blonde hair stretched the least before breaking. Black hair stretched the second furthest and ginger hair stretched the 3rd furthest. The frame of length of hair stretched (from my results) before breaking is as follows Brown, Black, Ginger, and then Blonde.Brown hair undergo the highest crease before breaking and blonde hair go through the lowest air travel before breaking. The order of gillyflower experienced by hair (from my results) before breaking is as follows Brown, Black, Ginger, and then Blonde.Brown hair experienced the highest tensile underline value before breaking and blonde experienced the lowest tensile express value before breaking. The order of tensile sample experienced by hair (from my results) before breaking is as follows Brown, Ginger, Black, and then Blonde. graph 1 shows the middling force call for to break the four colours of hair. From this graph I can see that brown hair necessary the greatest force to break. Black hair also required a large amount of force to break and so did ginger hair. Black hair only required a small amount of more force to break then ginger hair. The breaking force required for brown, black and ginger hair was sort of similar. Blonde hair required much less force to break compared to the other colours of hair. This proves that the disulphide bonds in the blonde hair are not a sizeable advantage for strength of the hair. The darker the hair the stronger the force required for the bonds in the hair to break. The darker the hair the more resistant it is to breaking when forces are applied. The darker the hair the higher concentrations of melanin present along the hair cortex.The same sort of prescript is seen in graphs 2, 3, 4 and 5. represents 2, 3, 4 and 5 show the backstage of hair when mass es are added. Blonde hair breaks the earlier and brown hair breaks the latest.Graph 2 shows brown hair. Brown hair requires about 120g to cut through up to about 70mm before breaking. The graph follows a canonical disposition and there are no erroneous results. All results fit the line of outstrip fit.Graph 3 shows blonde hair. Blonde hair requires about 80g to extend up to about 35mm before breaking. The graph follows the basic trend and most results fit the line of surmount fit. There is one anomaly, though. The book of facts should not increase and then decrease. It should keep on decreasing. There must have been an error in recording this result. The results in graphs 2, 3, 4 and 5 are all modal(a)s. To work out the blonde set in table 32, the results in tables 12, 13, 14, 15, 16 and 17 were used. There was only one value for the annex at 80g, in table 15. This value was smaller than the fountainable of all the extensions in all six tables. This sample of hair should have broken at 80g not 90g. This did not happen. This may have been an error in not measuring correctly.Graph 4 shows ginger hair. Ginger hair requires about 100g to extend up to about 60mm before breaking. The graph follows the basic trend until it gets to 55g point. From this point forrad the hair length increases and decreases dramatically. This should not happen. The reason why this happens is described above with the blonde hair. It is an error in measuring.Graph 5 shows black hair. Black hair requires about 140g to extend up to about 65mm before breaking. This graph is perfect. There are no anomalies. All points meet the line of best fit accurately.Graph 6 shows the average stresses and strains experienced by each hair colour. All four hair colours are plotted on the same graph so they can be easily compared against each other. Brown, blonde and ginger hairs do not follow the familiar trend. The stresses and strains for these three should continue to increase. Tables 57, 58 , 59 and 60 show where the stress and strain values came form. The results are like this because when the stress and strain values were calculated the average extensions were used, which had a few faults, as describe above.Graphs 7, 8, 9 and 10 show clearly what is natural event to the stress-strain curves. Graph 7 shows one wild result. It has a high stress and strain value. Graph 8 also shows only one anomalous result. These two graphs show the basic trend. Graph 9 shows the practice trend until the stress value gets to 150Nm-2. Then it decreases and goes back on itself. This should not happen. The reason for this is explained above. There is an error in the extension averages. Graph 10 shows no anomalies.Graphs 11, 12, 13 and 14 show hold ined values for stress and strain in all colours of hair. Graph 11 shows the modified stresses and strains for brown hair. This graph does not change shape backwards and the stress and strain values do not decrease. Graph 12 shows the modif ied stresses and strains for blonde hair. This graph does not show values of stress and strain decreasing. Graph 13 shows the modified stresses and strains for ginger hair. This graph has changed a lot. It reads much clearer. Stress and strain increases throughout. This is exactly what the graph should look like. Graph 14 is the same as graph 10. It did not need any modifications.The punk rockness of a hair is measured of its resistance to break. A lot of goose egg is required to break a tough material. Finally, the strength of a material (or tensile strength) is the greatest tensile stress it can undergo before breaking.Hair is an elastic material it can stretch to a certain maximum point (elastic point) before breaking. The largest tensile stress that can be applied to a material before it breaks is known as its last-ditch tensile stress (UTS). This value is sometimes referred to as the materials breaking stress.Graph 7 shows the stress-strain points for brown hair. Graph 11 sh ows a modified var. of this. The UTS for brown hair is 359.03. Graph 8 shows stress-strain points for blonde hair. Graph 12 shows a modified reading material of this. The UTS for blonde hair is 125.48. Graph 9 shows the stress-strain for ginger hair. Graph 13 shows a modified version of this. The UTS for ginger hair is 286.58. Graph 10 shows the stress-strain points for black hair. Graph 14 shows a modified version of this. The UTS for black hair is 158.31.Overall I can see that brown hair was the strongest. This was not expected. I expected black hair to have the highest tensile strength, as it had a higher density of melanin along the cortex. Blonde hair turned out to be the one with the lowest tensile stress. Ginger haired people have a high density of the pheomelanin pigments in their hair fibre. Those who produce virtually no eumelanin have a red to orange colour depending on the density of the pigment in the hair fibre. Red haired people who have a greater relative proportio n of eumelanin production have a deeper red to red brown colour. Ginger hair also should have a high tensile strength. This is what I saw in my results. Black hair should also have a high tensile strength. My results showed black hair to have high tensile strength but not the highest.There are other ways in which hair tensile strength could have been measured. Hair products like shampoos have an effect on hair tensile strength. They are now designed to change hair strengths. Different makes of hair shampoos could be used. Strength could be measured in a similar way to how I measured it. A control will be also be needed, with hair with no products added.These modifications in Graphs 11, 12, 13 and 14 show what the stress strain graphs should look like. In Graphs 7, 8, 9 and 10 thelines should not twist backwards.Statistical TestI will be using the (Chi squared test) X2.The formula for the Chi squared test is as followsX2 = ? (O E) 2 /EO = Observed valueE = Expected valueThe ((O E) 2) part of the formula considers the size of the difference between the observed and expected values. This difference could be either positive or negative. To forfend the mathematical problems associated with negative values, the difference is squared.The (E) part of the formula relates the size of the difference to the order of magnitude of the numbers involved.The sigma (?) sum symbol is required because there is not just one pair of observed and expected values, but several (in this case four).By taking all the observed values of stress from tables 57, 58, 59 and 60, I can work out the expected value for each hair colour.I can then place these values in a table and work out the value for X2, using the chi squared formula.E = ( OBrown + OBlonde + OGinger + OBlack ) / 4E = ( 297.3 + 121.5 + 246.7 + 158.3 ) / 4E = 205.95BrownBlondeGingerBlackO297.3121.5246.7158.3E205.95205.95205.95205.95( O E )91.35-84.4540.75-47.65( O E ) 28345713216612271(( O E ) 2) / E40.51934.6298.06311.02 5X2 = 40.519 + 34.629 + 8.063 + 11.025X2 = 94.235To calculate the degrees of license to be used can be found as follows* Number of categories minus 1.In this case 4 1 = 3The detailed value (taken from critical values for the Chi squared test) at 3 degrees of freedom is 7.81 (at the 5% level).The test statistic (X2 = 94.235) is greater than the critical value(C.V = 7.81, at the 5% significance level). We therefore can reject the null assumption and verbalise there is a significant difference between the observed aInvestigating the factors affecting tensile strength of human hairEvaluating (Skill D)Limitations* The selotape holding hairs in the paperclip at the top and at the bottom could have interfered with the tertiary structure of the protein, keratin. This could have increased or decreased the bond attractions in the hair to cause the hair to have a high or low tensile stress. This would make my results unreliable. The hairs masking higher tensile stress may just be showing how gluey the selotape is and how strongly it is holding the hair structure together. This though, would affect all my results, as all hair samples had selotape on them to hold them together at the top and at the bottom. So, this limit would affect all hairs making it a very weak limitation. My conclusion will not be affected as this limitation affects all hairs.* The time in between weights were added is another limitation. When each weight was added the hair stretched. But when there were a lot of weights on hair, the hair stretched quick and then the length was measured. After I finished measuring the hair had slowly stretched a little bit more. So the measurement was wrong. When the next weight was added tautological extension was added onto the new extension. My results were affected by this because some extensions were false making some data imprecise. Therefore, my conclusion will be invalid, because some hair samples could have broken at lower weights if I had waited fo r the hair to stretch, very slowly until it broke. There needed to be a time limit in which I had to record the extension of the hair, before adding the next weight to the hair.* The eye piece graticule can be a limiting factor. Different people measured hair thickness and record it to what they felt the thickness ought to be match to the scale. It was not very clear to see how thick the hair was, as the hair was faded under the microscope at all magnifications and the outline was difficult to see. This could affect my results as the thickness of hairs was used to calculate the cross sectional area of the hairs, which was then used to calculate the tensile stress experienced by the hair. This could make my tensile stress values incorrect. My conclusion therefore could be affected by making out that a certain coloured hair had a higher tensile stress than another coloured hair, when really it shouldnt have. This would make my conclusion unreliable.* There were different shades of ha ir colour, for example, there were light brown hair colours and dark brown hair colours. It was sometimes hard to distinguish between brown and blonde. This was the same for blonde hair. This would have an affect on the reliability and precision of my results making the the true of the strengths of different colours of colours of hair inaccurate. There should have been a certain shade of colour of hair (same amount of melanin in each brown hair) used for each colour sample. My conclusion will be imprecise because brown or blonde hair shades could cause incorrect results and make my conclusion incorrect.* The 10g mass is a limitation as the hair could break at lower masses than they actually did, for example a hair that broke at 50g could have broken at 41g, but I wouldnt know that as I only used 10g masses. So, I got false readings implying the hair is stronger than it actually is. If smaller masses were used my results would be much more accurate to make my conclusion reliable. Th is limitation could cause my conclusion to be invalid, causing the hairs strength and point on breaking higher or lower than it actually is. proofAfter doing my statistical test I can reject my null hypothesis and accept my hypothesis and say that brown, blonde, ginger and black hairs differ in tensile strength. I have proved this difference in my calculations, mainly in graphs 1 and 6. From my results I can see that darker coloured has a higher tensile stress compared to lighter coloured hairs. In my hypothesis I said that lighter coloured hair would have a higher tensile strength than darker coloured hair, due to lighter coloured hair having sulphur-sulphide bonds, which are very strong. I have disproved this. finished testing all four colours of hair I can see that these strong sulphur bonds do not reflect any tensile strength qualities. Lighter coloured hair does not have an advantage over dark coloured hair when it comes to tensile strength. It mainly depends on the type of me lanin the hair contains. The denser the melanin measuring is the stronger the hair.