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SCIENTIFIC METHOD & RESEARCH DISCUSSION KING’S COLLEGE CORE273 WHAT IS THE PURPOSE OF RESEARCH? • Research: systematic investigation into and study of materials and sources in order to establish facts and reach new conclusions. • Conducted for exploration, to describe, or to explain. • Can be directed or non-directed. • Three common types: • Pure research: conducted to find out something unknown by examining anything. • Original research: looking for information no one else has found. • Secondary research: finding out what others have discovered trying to reconcile conflicts, find new relationships, arrive at own conclusions. CHARACTERISTICS OF RESEARCH 1. Systematic: rules and procedures to ensure objectivity. 2. Logical: cycle of deductive and inductive reasoning. • Deductive: involves reasoning from general to specific. • Inductive: reasoning from specific to general. 3. Empirical: derived from observations of what exists. 4. Replicable: can be repeated with similar results in similar circumstances each time. 5. Transmittable: should be representative of a larger population. 6. Reductive: focused on a manageable piece. 7. Objective: removal of personal values and bias – suspension of belief. HOW SHOULD RESEARCH BE CONDUCTED? • The Scientific Method: “process by which scientists, collectively and over time, endeavor to construct an accurate (that is; reliable, consistent, and non-arbitrary) representation of the world”. 1. Observation and description of phenomenon. 2. Formulation of a hypothesis to explain phenomena. • An educated guess. • “Proposed explanation made of the basis of limited evidence as a starting point for further observation.” 3. Use of the hypothesis to make testable predictions. 4. Perform experimental tests/observations of the predictions and gather the appropriate data. 5. Accept or reject/modify the hypothesis AND REPEAT! EXPERIMENTS SHOULD BE CONTROLLED • Determine variables: factors that can change. • Independent: goes unchanged by other variables; manipulated by experimenter. • Dependent: changes due to the independent variable. • Confounding: unintentional changes to dependent or independent variables. • Randomly select a large group of appropriate subjects. • Create two groups; similar in all ways except independent variable. • Experimental: receives variable to be tested. • Control: receives placebo or replaced/absent variable. • Conduct experiment. • Collect detailed and appropriate data and measurements. • Analyze collected data. • Make conclusions, modify, and repeat. Elevation (independent) and boiling temperatures of water (dependent) Two samples, one is the control group and the other is the experimental group. Three samples. One is the control group and the other two are part of the experimental group. DATA TYPES • Quantitative Data: collected data are numbers and statistics. • Information will commonly be displayed in graphs and tables. • Statistics will help determine the significance of the data. • Qualitative Data: collected data are words, pictures, or objects. • Data displayed in varying manners depending on methods used. INTERPRETING DATA • Results can determine relationships between variables: • Correlation: two variables are closely related. • Causation: one variable causes another to occur. • Can you accept the hypothesis? • Does the data support what you thought? • Can you modify the hypothesis or experiment? • Could you make a better “guess”? • Could your experimental design be more solid? • Are there confounding variables? Bias? • Should you fully reject your hypothesis? • Not right away! Repeat and see what happens! WHAT DO WE DO WITH WHAT WE FIND? • Hypothesis becoming a theory; NOT IMMEDIATE! • “ The process of establishing a new scientific theory is necessarily a grueling one; new theories must survive an adverse gauntlet of…experts in their particular area of science; the original theory may then need to be revised to satisfy those objections. The typical way in which new scientific ideas are debated are through refereed scientific journals…before a new theory can be officially proposed to the scientific community, it must be wellwritten, documented, and submitted to an appropriate scientific journal for publication. If the editors of these prestigious publications accept a research article for publication, they are signaling that the proposed theory has enough merit to be seriously debated and scrutinized closely by experts in that particular field of science”. • It is vital to disseminate research; to spread or disperse. • Peer-reviewed Journals: collection of articles analyzed and critiqued by appropriate peers. Contain the most accurate information. HOW DO I READ A RESEARCH ARTICLE? • Become a skeptic. • Appreciate the value of statistics. • Learn to read graphs. • Distinguish anecdotes from scientific evidence. • Anecdotes are testimonial and unverified. • Separate facts from conclusions. • Fact is objective reality. • Conclusion: judgement reached by reasoning. • Correlation versus causation. • Know that science has its limits! RESEARCH AND THE HUMAN BODY • Knowledge of Anatomy (form) • Egyptian mummification (BC 1600-1550). • Herophilus and Erasistratus perform systemic cadaver dissections (3rd century). • Discontinued in Middle Ages, revived in Renaissance (12th century onward). • Andreas Vesalius published De Humani Corporis Fabrica (16th century). • Knowledge of Physiology (function) • Erasistratus “Father of Physiology” applied physical laws to human function. • William Harvey demonstrated heart pumps blood through vessels (1578-1657). • Anton van Leeuwenhoek 1st man to make and use real microscope (1632-1723). • Majority of our knowledge has been gained in the 20th century. • Many early experiments had no ethical boundaries. ETHICS IN HUMAN RESEARCH • “The whole discipline of biomedical ethics rises from the ashes of the Holocaust” (Robert Leiter, Tainted Science, Jewish World, July 14-20, 1989). • The Nuremberg Code (1947) establishes principles to guide physicians in human experimentation. • • When human subjects can not be ethically elected, animals are often used. DISEASE DISCOVERY Heart Disease Studied in dogs, rats, rabbits, cats, sheep, and pigs. Studies with dogs contributed to our most basic understanding of how to manage heart disease. Techniques to diagnose the workings of the heart— electrocardiography, cardiac catheters, angiograms, and coronary blood flow measurement—were developed through research using dogs, as were surgical techniques such as cardiac bypass, angioplasty, and heart transplants HIV/AIDS Our understanding of the retrovirus that causes HIV/AIDS comes in part from studies of similar viruses in chickens, cats, and monkeys. Promising drugs and possible vaccines are tested first in mice and monkeys before being used in clinical trials with human volunteers. Cancer The chicken provided one of the earliest models of how cancer grows and spreads. An understanding of how viruses cause tumors and the use of hormone treatments to limit tumor growth were developed using rats, mice, rabbits, chickens, monkeys, and horses. Cancer treatments such as chemotherapy drugs, radiation therapy, and various surgical techniques were developed using rodents, dogs, and monkeys, among others. Bacterial Infections The effectiveness of penicillin and other antibiotics as treatments for bacterial infections was established through research using mice and other rodents. Scientists continue to use animals to determine what antibiotics are effective against specific organisms, their toxicity, and their potential side effects. WHY DO I NEED TO KNOW THIS, HERE? • Yes, the form and function of the human body is pretty well understood, BUT: • Sometimes things go wrong! • Disease ravages the body, medications become obsolete (think “antibiotic resistance”). • What we have now could be better! • Technology could make surgery less invasive, treatments more effective. • As living things, humans can adapt and evolve. • ASPM is a brain size regulator of increasing levels in younger individuals. • Sometimes we learn that we just weren’t “right” to begin with. SOURCES • • • • • • • • • • • • – citation for table. • aptive%20evolution%20of%20ASPM,%20a%20brain%20size%20determinant%20in%20Homo%20sapiens.pdf
Worksheet Eight CORE273 SUM18 NAME: Scientific Method and Research 1. Find one peer-reviewed journal article (about anything at all) and hand it in with this worksheet. You do not have to read it, but it MUST be from a credible scientific journal – not a magazine article, web blog, facebook page, etc. Use the school library or Google Scholar to help you find something. It is important that you know where to find valid research. 2. Using the steps for the scientific method as well as the elements of a controlled experiment (slides 4 and 5), create hypothesis and experiment based upon your own observations (even if it is something that you already know the outcome of). Do not worry about creating data – simply state which type of data you would collect. a. EX: I observe that after I drink soda, I get the hiccups. I hypothesize that the bubbles in carbonated beverages likely result in burps or hiccups in most people. I can test this by comparing the response of a large group of individuals to different drinks. I will have a control group that will drink only water. The experimental group will drink carbonated water (to attempt to control for all other substances in sodas and focus primarily on the bubbles). The two groups will drink their specified drink at the same time of day, as close to the same pace as possible, out of identical cups, and the same amount of fluid. They will be observed for their response (hiccups or burps). This qualitative data will be analyzed to determine the correlation between carbonation and hiccups/burps.

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The Relationship between Wi-Fi Access and Youtube Usage
Institution affiliation



Hypothesis, Control and Experimental Groups
Access to Wi-Fi or free internet increased the rate at which students use YouTube. To test
this hypothesis, I made four groups, each with twenty students and put them in a different
environment. Two groups were given the same task, involving doing research through the
internet. The remaining two groups were not given any assignments. One of the groups without
assignment was put in an environment with free internet and the other without free internet.
The Experiment and Observations
The group with no assignment and free internet was the control experiment. All the other
factors were constant across all groups. Each student had his or her laptop or smartphone and
time allocated to each group was the same. The usage of YouTube by each group was observed
in all the groups and properly analyzed. The analysis would involve a step-by-step check of the
students’ browser history and data usage statistics. The latter is easily accessible by following the
following simple steps: with the smartphone operating on iOS or Android, go to settings> data
usage> scroll down and observe the highest ranking applications and the data used by each app.
Inferences, Interpretations and Conclusion
On analysis of the data collected, the group without a task and having an unlimited access
to internet used YouTube the most as indicated by the data usage statistics on the phones and
laptops’ browser histories. This was followed by the group with an assignment and unlimited
access to the internet. The two remaining groups used YouTube very partially. Through the
analysis, I, therefore, accepted my hypothesis and concluded that access to Wi-Fi or free internet
increased the rate at which students used YouTube.

Phys . Med . Biol., 1980. V01. 25 . No . 3. 405-426 . Printed in Great Britain

Review Article

Ultraviolet radiation physics and the skin
B L Diffey:
Medical Physics Department. Kent andCanterbury

Hospital. CanterburyCT1

3NG .

This review was completed in June 1979

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 . Physics and measurement of natural and artifical uv sources . . . . . .
2.1. Thenature of ultravioletradiation
. . . . . . . . . . . . . . .
2.2. The production of ultravioletradiation
. . . . . . . . . . . . .
2.3. Artificialsources of ultraviolet radiation used in photobiology . . .
2.4. Solarradiation . . . . . . . . . . . . . . . . . . . . . . . .
2.5. Measurement of ultravioletradiation
. . . . . . . . . . . . . .
2.6. Ultravioletradiationdosimetry
. . . . . . . . . . . . . . . .
2.7. Isolation of spectralregions
. . . . . . . . . . . . . . . . . .
3 . Theskin
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1. Thestructure of the skin
. . . . . . . . . . . . . . . . . . .
3.2. Optics of theskin
. . . . . . . . . . . . . . . . . . . . . .
4 . The biological effects of ultraviolet radiation in normal skin . . . . . .
4.1. Ultravioleterythema
. . . . . . . . . . . . . . . . . . . . .
4.1.1. The mechanism of u v erythema
. . . . . . . . . . . .
4.1.2. The actionspectrumforerythema
. . . . . . . . . . . .
4.2. Melanin
. . . . . . . . . . . . . . . . . . . .
4.3. Production of vitamin D
. . . . . . . . . . . . . . . . . . .
4.4. Aging of theskin
. . . . . . . . . . . . . . . . . . . . . .
4.5. The carcinogenicnature of ultravioletradiation
. . . . . . . . .
4.6. Models of skincancerincidence
. . . . . . . . . . . . . . . .
5 . The current involvement of medical physics with ultraviolet radiation
. .
5.1. Protectionagainstultravioletradiation
. . . . . . . . . . . . .
5.2. Photochemotherapy . . . . . . . . . . . . . . . . . . . . .

42 1


1 Introduction
The role of sunlight in the causation of biological effects in the human skin has been
evident for many centuries. The importanceof sunlight for the maintenanceof health
was realised by the ancient Assyrians. Babylonians. Egyptians. Greeks and Romans.
was practised by the ancient
and the worship of the sun as a health-bringing deity
Germans andby the Incasof South America (Ellinger1957). However. it is only in the
f Present address: Regional Medical Physics Department. Durham Area Unit. Dryburn Hospital. Durham
DH1 5TW. England .


@ 1980 The

of Physics



B L Diffey

last hundred years or so that the scientific investigation of the effects of light, both
beneficial and harmful, has begun.
In 1666 Isaac Newton'. . . procured me a Triangularglass-Prisme, to try therewith
the celebrated Phaenomena of Colours'andtherebyexplainedthepolychromatic
nature of light. It was not until 1801 that Johann Ritter discovered the ultraviolet
region of the solar spectrum (Meyer 1952) and showed that
chemical action was caused
by some form of energy in the dark portion beyond the violet. Modern ultraviolet
photobiology started with the work of Niels Finsen, who by sound experimentation
during the years1893-96 proved that sunburn was caused by the ultraviolet radiation
(UVR)of the sun's spectrum and notby the radiant heat, as the name
implies. Although
a clinician, whose name is especially associated with the first successful therapy for
Lupus vulgaris, his approach was very much that of a scientist. His goal
was the efficient
exploitation of U V R therapy in medicine, but he also spent much time examining the
basic physical characteristics of U V R (Magnus 1978).
Following the pioneeringwork of Finsen, theearly part of the twentieth centurysaw
the rapid expansion of heliotherapy and actinotherapy throughout Europe and the
United States of America. In his book on sunlight andhealthpublished in 1926,
Saleeby discusses with much enthusiasm the benefits of heliotherapy and in particular
describes thework of Dr Rollier at Leysinin the Alpes Vaudoises, whose experiencein
twenty years of successful treatment of surgical tuberculosis by natural sunlight has
included '. . . many extreme cases of spinal tuberculosis, with paralysed lower limbs,
tuberculosis of every other partof the body,of course, includingthe lungs, rickets, many
of the longeststanding,wounds of war,non-healing
operative wounds,osteomyelitis, bed-sores and so on' (Saleeby 1926). In the preface to
the third edition of his book Saleeby notes the formation of the Sunlight League in
London in 1924 and states as one
of itsaims "the education of the public to the
appreciation of sunlightasa means of health; teaching the nation that
sunlight is
Nature's universal disinfectant, as well as a stimulant and tonic.' It
is interesting to
contrast this statement with the view of many leading dermatologists at the VIIth
International Congressof Photobiology held in Rome in 1976, whereit was maintained
that excessive or even moderate exposure sunlight
was harmful. It was suggested that
when we get up in the morning, after we have cleaned our teeth, we apply our sun
barrier lotion!
The interaction of ultravioletradiation in the skin leadingtoamacroscopic
biological effect encompasses several seemingly unconnected areas
of knowledge; from
meteorology through photophysics, photochemistry and
cellularbiology to clinical
dermatology and oncology. It is not appropriate or possible in the present review to
include the photochemistry and cellular biology associated withuv interactions in the
skin but for a good, recent monograph see Jagger (1967). Instead the
review will limit
itself to the beginning and endof the chain of events: the specification of U V R sources
and optics of the skin, and the observable biological effects.

2. Physics and measurement of natural and artificial uv sources
2.1. The nature of ultraviolet radiation

Ultraviolet radiation is part of the electromagnetic spectrum and
lies between the
visible spectrum and the x-ray region. The Commission Internationale de 1'Eclairage
(1970), amongst others, has divided the wavelengths between 400 and 100 nm into

Ultraviolet radiation physics andthe skin


three regions:






280-100 nm.

These regions have widely differing physical properties and potential for causing
biological damage. UVR in the region 200 to 100
nm is readily absorbed in air andso has
little opportunity to producebiological effects, apart from the indirecteffects resulting
from the production
of ozone andof oxides of nitrogen in the air. In the case
of mercury
vapour lamps with transparent vitreous silica envelopes, most the ozone production is
probably due to the 185 nm line (Koller 1952).

2.2. The production of ultraviolet radiation
by theheating of abodytoan
by theexcitation of a gas discharge(Hendersonand
Marsden 1972).
A body heated to ahigh temperature radiates as a resultof its constituent particles
becoming excited by numerous interactions andcollisions. For a perfect black body the
power radiated at anywavelength from unit surface area of such a body is determined
solely by its temperature in accordance with Planck's law, which is



A '[exp(B/AT) - l]

where M,, is the spectral radiant exitance at wavelengthA, T is the absolute temperature of the radiator, and A and B are constants.
As the temperature is raised, not only does the maximum power radiated increase
rapidly, but the peakof the emission curve moves to ashorter wavelength. The sun,of
course, is themostcelebratedsource
of incandescent UVR. However artificial
incandescent sources are not efficient emitters of UVR: the ultraviolet emission from a
general purpose tungsten filament lamp is only 0.08% of the rated power for a 40 W
lamp, rising to 0.1% for a 100 W lamp and 0.17% for a 1 kW lamp (Summer 1962).
In a discharge tube, across
which there is an electricfield, the electrons drift towards
the anode and the
positive ions towards the cathode. In a low pressure discharge (a few
Torr) such as occurs in a fluorescent lamp for example, one of three events may take
place when a free electroncollides with a neutral gas atom. The electronmay undergo
an elasticcollision, theatom may be excited ortheatom
may beionised. In a
fluorescent lamp containing a mixture
of mercury and argon, the mercury
is preferentially ionised since its ionisation potential (10.4 eV) is lower than that of argon
(15.7 eV). The inertgases present in most practical discharge lamps act to reduce ion
losses to the wall by ambipolar diffusion, to control the mobility of the electrons, to
provide easier breakdown at a lower striking voltage and to prolong the life of the
electrodes by reducing sputtering and evaporation (Henderson and Marsden 1972).
For a discharge to operatein a steady condition the rateof ionisation must exactly
balance the rate of loss of electrons and ions by ambipolar diffusion to the walls. The
consequence of this is that thereis no simple relationship between voltage and current.
The electrical characteristic of the discharge is very complex and dependenton all the

B L Diffey


constituents of the discharge and conditionsof operation. In general the discharge has a
‘falling characteristic’: the volt-ampere curve has a negative slope (Koller 1952).
Most of the radiation from the majority of discharge lamps is from the positive
column, i.e. the large uniform region
of the discharge between the electrodes. The
energetic electrons which produce the ionisation also produce excitation of the gas
atoms which subsequently radiate at their characteristic frequencies. Figure 1 shows a
few of the excitation and radiating transitionsin lamps containing mercury vapour.

7 73




L 89

P L67

Green Blue Vlolet
5L61 L35 8 LOL 7



t ‘





2 5 3 7nm





Figure 1. Simplified energy transition diagram for mercury (from Henderson and Marsden

As the pressure in a discharge tube is raised to a few atmospheres, two principal
changes occur:
(1) the gas temperature increases due to the
increasing number of collisions (mainly
elastic collisions) with the energetic electrons; and
(2) thehigh temperature becomes localised at the centreof the discharge, there now
being a temperature gradient towards thewalls, which are much cooler.
The wall becomesmuch less importantat high pressures,andnotaltogether
essential: discharges can operate between two electrodes without any restrainingwall,
and are then referred as
to arcs. At high pressures thecharacteristic lines presentin the
low pressure discharge spectrum broaden to give a virtually continuous spectrum.
For a much more detailed description of lamp performance and technology the
reader is referred to thebrief article by Beeson (1978) or
to the textbooksby Henderson
and Marsden (1972), Summer (1962) andKoller (1952).
2.3. Artificial sources of ultraviolet radiation used in photobiology
The most common artificial sources of UVR currently used in photobiology are the
xenon arc, mercury vapour arcs operating at various pressures and mercury discharge
lamps used with or withoutfluorescent coatings. For a historical review of the artificial
production of UVR see Schafer (1969).
The spectral emission from a xenon arc lamp operating at several atmospheres is
similar to that of the uv component of the solar spectrum. An apparatus consisting of a
150 W xenon lamp, collecting optics, spectral shaping components and a refocusing lens


and the skin


phototesting human skin (Urbach 1969a). The output spectrum

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