3.6: Communication Process
The communication process may be explained by means of a linear model of communication, interactive model of communication or transactional model of communication [ 11 ].
Linear Model of Communication
Linear model of communication entails a sender, a message, a receiver and noise (Figure 3.6.1).
Interactive Model of Communication
Interactive model of communication gives a slightly more complex explanation of the communication process. Communication is seen as a process in which the listener gives feedback or responds to a message after a process of interpretation. A communicator creates and interprets a message with a personal field of expertise and/or a frame of reference Figure 3.6.2).
Transactional Model of Communication
Transactional model of communication acknowledges and gives emphasis to the dynamic nature of interpersonal communication and the multiple roles of the communicators. Features such as time, messages, noise, fields of experience, frames of reference, meanings, shared systems of communicators and personal systems all pay a role in the process of communication. Communicators often participate simultaneously (sending, receiving and interpreting). The unique interpretive and perceptual processes of individuals thus play an essential role in the communication process.


9.6: Concluding Comments
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Economists have long held that advertising has been a means of influencing consumer preferences in a manner that makes demand less elastic and gives further discretion in price setting. The argument here is that advertising is way for sellers to increase their market power in an imperfectly competitive market. This argument is not without merit but does not explain the breadth and differences in advertising messages observed in real world commerce. Furthermore, if this were the only purpose of advertising, it would be difficult to defend it as a valuable use of economic resources. Advertising would be doing nothing to make the economy more productive. Its sole purpose would be to transfer wealth from buyers to sellers and would probably worsen welfare losses that result from resource misallocation problems observed in models of imperfectly competitive behavior. As such, advertising would be a prime candidate for regulation or even prohibition under laws similar to those that prohibit collusion, price fixing, or other anti-competitive behavior.
Recent work in information economics has noted that advertising can facilitate consumer search and can provide believable signals about experience attributes that cannot be verified pre-sale. Economists are developing a deeper understanding of advertising and its role in a market economy. If advertising does aid search and mitigate problems of asymmetric information, then it plays a valuable role that can facilitate the functioning of markets.


18: Northern blot and Southern blot
Summary
Northern blot (RNA) and Southern blot (DNA) are methods used to detect the presence of a particular nucleic acid sequence in a mixture.
Also known as
No alternative names
Nomenclature note: The Southern blot is named after its inventor, Edward Southern, and therefore, the word “Southern” is a proper noun and should always be capitalized in its name. However, the northern blot and western blot were named in reference to the Southern blot and the cardinal directions. Therefore, the words “northern” and “western” in the method names are not proper nouns, and should not be capitalized.
Samples needed
Mixtures of nucleic acids
Method
The overall methods for northern and Southern blots are very similar, although they are used to detect different molecules, RNA and DNA, respectively. The first step is to separate the nucleic acid mixture by gel electrophoresis . Following electrophoresis, the nucleic acids are transferred to a membrane, then the membrane is treated with a single-stranded nucleic acid probe. If using double-stranded nucleic acid samples, a denaturing step is required to expose the nitrogenous bases.
The probe has two key features. First, it is able to base pair with the DNA or RNA sequence of interest. Second, it is labeled for visualization, often either by a radioactive or fluorescent molecule. When the membrane is visualized, the signal indicates the size (due to the electrophoresis step), and to some extent, the amount of the nucleic acid sequence of interest.
Controls
Ideally, there should be positive and negative controls to test the specificity of probe binding. The electrophoresis step should also include molecular weight ladders.
Interpretation
Figure 1 above shows the results of a two Southern blots, the first from embryonic stem cells that the authors were attempting to genetically modify, and the second from the resulting genetically modified mice. Importantly, the ES cells being used already had a modification that allowed researchers to easily insert a gene of interest. Therefore, when the genomic DNA was cut with the restriction enzyme SpeI, three band sizes were possible. The wild type locus is shown by the 6.2 kb band, the initial modification (to allow a transgene to be inserted) is shown by a 6.7 kb band, and the locus with the gene of interest ( PHGDH ) successfully inserted is shown by a 4.3 kb band.
In panel B, ES cell clones D2, D6, and D7 show one wild type locus and one modified locus without PHGDH ( bands at 6.2 and 6.7 kb). Clones D4 and D5 show one wild type locus and one locus with PHGDH (bands at 6.2 and 4.3 kb). Clone D1 has a band at an unexpected size, so that would not be a good clone to select to use to make genetically modified mice. Panel C shows that, as expected, mice that have been PCR genotyped as having two copies of PHGDH (“tetO/tetO”) have only the 4.2 kb band, mice with no transgene (“+/+”) have only the 6.2 kb band, and mice with one copy of PHGDH (“tetO/+”) have both bands.
Note that when all of the DNA in a mouse cell is digested with SpeI, a huge smear of DNA would be seen on a DNA gel if a normal gel visualization method like ethidium bromide were used. The use of a probe complementary to the locus of interest allows the researchers to see only the bands they care about, not every single SpeI fragment.
Image Descriptions
Thumbnail
"Southern blot membrane.jpg" ↗ by Bojan Žunar is licensed under CC BY-SA 4.0 ↗.
Description: Southern blot membrane.
Author
Katherine Mattaini, Tufts University
- Mattaini, K. R., M. R. Sullivan, A. N. Lau, B. P. Fiske, R. T. Bronson, and M. G. Vander Heiden. 2019. Increased PHGDH expression promotes aberrant melanin accumulation. BMC Cancer 19:723. ↵


22.5: Gas Exchange
By the end of this section, you will be able to:
- Compare the composition of atmospheric air and alveolar air
- Describe the mechanisms that drive gas exchange
- Discuss the importance of sufficient ventilation and perfusion, and how the body adapts when they are insufficient
- Discuss the process of external respiration
- Describe the process of internal respiration
The purpose of the respiratory system is to perform gas exchange. Pulmonary ventilation provides air to the alveoli for this gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting. It is through this mechanism that blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body.
Gas Exchange
In order to understand the mechanisms of gas exchange in the lung, it is important to understand the underlying principles of gases and their behavior. In addition to Boyle’s law, several other gas laws help to describe the behavior of gases.
Gas Laws and Air Composition
Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table \(\PageIndex{1}\)). Partial pressure ( P x ) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure \(\PageIndex{1}\)). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.
| Gas | Percent of total composition |
Partial pressure
(mm Hg) |
|---|---|---|
| Nitrogen (N 2 ) | 78.6 | 597.4 |
| Oxygen (O 2 ) | 20.9 | 158.8 |
| Water (H 2 O) | 0.4 | 3.0 |
| Carbon dioxide (CO 2 ) | 0.04 | 0.3 |
| Others | 0.06 | 0.5 |
| Total composition/total atmospheric pressure | 100% | 760.0 |
Partial pressure is extremely important in predicting the movement of gases. Recall that gases tend to equalize their pressure in two regions that are connected. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower. In addition, the greater the partial pressure difference between the two areas, the more rapid is the movement of gases.
Solubility of Gases in Liquids
Henry’s law describes the behavior of gases when they come into contact with a liquid, such as blood. Henry’s law states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas. The greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid. For example, although nitrogen is present in the atmosphere, very little nitrogen dissolves into the blood, because the solubility of nitrogen in blood is very low. The exception to this occurs in scuba divers; the composition of the compressed air that divers breathe causes nitrogen to have a higher partial pressure than normal, causing it to dissolve in the blood in greater amounts than normal. Too much nitrogen in the bloodstream results in a serious condition that can be fatal if not corrected. Gas molecules establish an equilibrium between those molecules dissolved in liquid and those in air.
The composition of air in the atmosphere and in the alveoli differs. In both cases, the relative concentration of gases is nitrogen > oxygen > water vapor > carbon dioxide. The amount of water vapor present in alveolar air is greater than that in atmospheric air (Table \(\PageIndex{2}\)). Recall that the respiratory system works to humidify incoming air, thereby causing the air present in the alveoli to have a greater amount of water vapor than atmospheric air. In addition, alveolar air contains a greater amount of carbon dioxide and less oxygen than atmospheric air. This is no surprise, as gas exchange removes oxygen from and adds carbon dioxide to alveolar air. Both deep and forced breathing cause the alveolar air composition to be changed more rapidly than during quiet breathing. As a result, the partial pressures of oxygen and carbon dioxide change, affecting the diffusion process that moves these materials across the membrane. This will cause oxygen to enter and carbon dioxide to leave the blood more quickly.
| Gas | Percent of total composition |
Partial pressure
(mm Hg) |
|---|---|---|
| Nitrogen (N 2 ) | 74.9 | 569 |
| Oxygen (O 2 ) | 13.7 | 104 |
| Water (H 2 O) | 6.2 | 40 |
| Carbon dioxide (CO 2 ) | 5.2 | 47 |
| Total composition/total alveolar pressure | 100% | 760.0 |
Ventilation and Perfusion
Two important aspects of gas exchange in the lung are ventilation and perfusion. Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible. However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced.
The partial pressure of oxygen in alveolar air is about 104 mm Hg, whereas the partial pressure of oxygenated blood in pulmonary veins is about 100 mm Hg. When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high. In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops. Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem. In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation. This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation. At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and pH levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli.
Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow.
Gas Exchange
Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up. External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.
External Respiration
The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries. These pulmonary capillaries create the respiratory membrane with the alveoli (Figure \(\PageIndex{2}\)). As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes (red blood cells) and binds to a protein called hemoglobin, a process described later in this chapter. Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli. Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter.
External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries.
Although the solubility of oxygen in blood is not high, there is a drastic difference in the partial pressure of oxygen in the alveoli versus in the blood of the pulmonary capillaries. This difference is about 64 mm Hg: The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg. This large difference in partial pressure creates a very strong pressure gradient that causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood.
The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary. However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar.
Internal Respiration
Internal respiration is gas exchange that occurs at the level of body tissues (Figure \(\PageIndex{3}\)). Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low, about 40 mm Hg, because oxygen is continuously used for cellular respiration. In contrast, the partial pressure of oxygen in the blood is about 100 mm Hg. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue. Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy in color.
Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood. It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg. The blood is then pumped back to the lungs to be oxygenated once again during external respiration.
Everyday Connection
Hyperbaric Chamber Treatment
A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber (Figure 22.24). Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia. Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized.
Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures.


18: The Cytoskeleton and Cell Motility
-
- 18.1: Introduction
- The cell as it appears in a microscope was long thought to be a bag of liquid surrounded by a membrane. The electron microscope revealed a cytoskeleton composed of thin and thick rods, tubes and filaments. Other intracellular structures and organelles are enmeshed in these microfilaments, intermediate filaments and microtubules. We will compare the molecular compositions of these structures and their subunit proteins.
-
- 18.2: Cytoskeletal Components
- Most eukaryotic cells look like a membrane-bound sac of cytoplasm containing a nucleus and assorted organelles in a light microscope. In the late 19th century, microscopists described a dramatic structural re-organization of dividing cells. In mitosis, duplicated chromosomes (i.e., chromatids) condense in the nucleus just as the nuclear membrane dissolves. Spindle fibers emerge and then seem to pull the chromatids apart to opposite poles of the cell.
-
- 18.3: The Molecular Structure and Sub-Cellular Organization of Cytoskeletal Components
- Of the three main cytoskeletal fibers, intermediate filaments serve a mainly structural role in cells. Microtubules and microfilaments have dual functions, dynamically maintaining cell shape and enabling cell motility. For example, when attached to the plasma membrane, microfilaments maintain cell shape. However, by interacting with motor proteins (e.g., myosin), they can pull or push against a muscle cell membrane, changing the shape of the cell.
Thumbnail: Image of a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in pink (Public Domain; Afunguy ).


4.1: Introduction
-
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Exhibit 4.1 (Credit: pxhere / Attribution CC0 Public Domain)
Learning Outcomes
After reading this chapter, you should be able to answer these questions:
- What are the advantages and disadvantages of the sole proprietorship form of business organization?
- What are the advantages of operating as a partnership, and what downside risks should partners consider?
- How does the corporate structure provide advantages and disadvantages to a company, and what are the major types of corporations?
- What other options for business organization does a company have in addition to sole proprietorships, partnerships, and corporations?
- What makes franchising an appropriate form of organization for some types of business, and why does it continue to grow in importance?
- Why are mergers and acquisitions important to a company’s overall growth?
- What current trends will affect the business organizations of the future?
EXPLORING BUSINESS CAREERS
Jessica MacLean
Sole Proprietor In most any elementary school classroom, at least one child’s answer to the question, “What do you want to do with your life?” will be, “A lawyer.” One of the most popular careers, lawyers are powerful figures in society, shaping our laws and ensuring that we adhere to them. Their prominence and power have led to the stereotype of rich, career-driven lawyers, often leaving no room in our minds for those who truly want to bring justice to the world. However, Jessica MacLean, a lawyer focusing primarily on women’s rights, is quick to say that, as with many stereotypes, that is only one side of the story. “I know because I lived that—I was on my way to being a successful corporate lawyer. But I realized what I was doing and how different that was from why I’d started practicing. So I walked away from it all to start my own practice.”
Nervous about the prospect of private practice, she has chosen to operate as a sole proprietorship for now. Sole proprietorships are easy to set up for people who want to work on their own, prefer direct control of the business, and desire the flexibility to sell the business or close the doors at any time. “For me, it’s the best choice because I am not responsible for or to anyone else. I can easily dissolve the business if I find it is not proceeding how I’d planned. More positively, too, if it does succeed, I know that success is due to my hard work.
Indeed MacLean’s law career was not always in corporate law. She turned her sights toward law after a gender and communications professor at DePaul University suggested her argumentative style might be an asset in that profession. “She said I needed to tone it down for class—that the other students seemed afraid to speak up—but then asked if I’d ever considered being a lawyer.” MacLean, who had always been interested in issues of justice and legality surrounding women, took her professor’s advice and made the leap into law.
While in law school, she clerked for the city of Chicago in their department of personnel’s sexual harassment office and volunteered for the Cook County state’s attorney’s office in the domestic violence division. The cases she worked on were emotionally trying. Despite the difficulty of the cases, she was drawn to them, compelled by the people she helped and the change she was able to effect. After school, she continued in related practice, working first for the Cook County state’s attorney’s office.
After several years with the state’s attorney’s office, she needed a change. It was then that MacLean decided to work for a corporation, a form of business that you will learn about in this chapter. “Why did I switch to corporate law? I think I was burnt out, to some extent. It’s so hard to work on those cases, day after day. I needed to see if I would be better somewhere else.”
Having enjoyed the rewards of working with the state’s attorney’s office and a corporation and being a sole proprietor, in 2014 MacLean joined a limited liability partnership (LLP, a form of business that you will learn about in this chapter) firm in Chicago. As her needs changed, the form and type of business organization she has worked for has changed also.
This chapter discusses sole proprietorships, as well as several other forms of business ownership, including partnerships and corporations, and compares the advantages and disadvantages of each.
With a good idea and some cash in hand, you decide to start a business. But before you get going, you need to ask yourself some questions that will help you decide what form of business organization will best suit your needs.
Would you prefer to go it alone as a sole proprietorship, or do you want others to share your burdens and challenges in a partnership ? Or would the limited liability protection of a corporation, or perhaps the flexibilit y of a limited liability company (LLC), make more sense?
There are other questions you need to consider too: Will you need financing? How easy will it be to obtain? Will you attract employees? How will the business be taxed, and who will be liable for the company’s debts? If you choose to share ownership with others, how much operating control would they want, and what costs would be associated with that?
As Table 4.1 illustrates, sole proprietorships are the most popular form of business ownership, accounting for 72 percent of all businesses, compared with 10 percent for partnerships and 18 percent for corporations. Because most sole proprietorships and partnerships remain small, corporations generate approximately 81 percent of total business revenues and 58 percent of total profits.
Most start-up businesses select one of these major ownership forms. In the following pages, we will discover the advantages and disadvantages of each form of business ownership and the factors that may make it necessary to change from one form of organization to another as the needs of the business change. As a company expands from small to midsize or larger, the form of business structure selected in the beginning may no longer be appropriate.


5.1: Communication Theory Overview
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A common place for this debate occurs in school textbooks—should they teach creationism or the big bang theory? How you answer this question depends on the theoretical perspective you hold. In either case, your theoretical perspective includes some common features—-reasons to justify your theory and evidence you use to prove that it is correct. Creationists cite the Bible or other religious texts as proof of their theoretical perspective. Advocates of the big bang theory argue that the earth emerged 13.7 billion years ago and cite the continued expansion of space (Hubble’s Law) as verifiable proof that this theory is correct. But how do we know which theory is right? Let’s apply this same reasoning to communication. Think about the many ways you develop, and try to answer, questions about the “right” ways to communicate.
We want to leave the intricacies of the theoretical debate between creationism and the big bang theory to our colleagues in the physical sciences, religious studies, and philosophies. However, we’ll use this chapter to explore theoretical issues relevant to the study of Communication. By the end of this chapter you should understand what communication theories are, their functions, how we evaluate them, and the five major theoretical paradigms shaping Communication study today. You’ll also discover just how important communication theory is to your everyday life.


Section 3: Semantics for identity
Identity is a special predicate of QL. We write it a bit differently than other two-place predicates: \(x\) = \(y\) instead of \(Ixy\). We also do not need to include it in a symbolization key. The sentence \(x\) = \(y\) always means ‘\(x\) is identical to \(y\),’ and it cannot be interpreted to mean anything else. In the same way, when you construct a model, you do not get to pick and choose which ordered pairs go into the extension of the identity predicate. It always contains just the ordered pair of each object in the UD with itself.
The sentence ∀\(xIxx\), which contains an ordinary two-place predicate, is contingent. Whether it is true for an interpretation depends on how you interpret \(I\), and whether it is true in a model depends on the extension of \(I\).
The sentence ∀\(x\) \(x\) = \(x\) is a tautology. The extension of identity will always make it true.
Notice that although identity always has the same interpretation, it does not always have the same extension. The extension of identity depends on the UD. If the UD in a model is the set {Doug}, then extension(=) in that model is {<Doug, Doug>}. If the UD is the set {Doug, Omar}, then extension(=) in that model is {<Doug, Doug>, <Omar, Omar>}. And so on.
If the referent of two constants is the same, then anything which is true of one is true of the other. For example, if referent(\(a\)) = referent(\(b\)), then \(Aa\) ↔ \(Ab\), \(Ba\) ↔ \(Bb\), \(Ca\) ↔ \(Cb\), \(Rca\) ↔ \(Rcb\), ∀\(xRxa\) ↔ ∀\(xRxb\), and so on for any two sentences containing \(a\) and \(b\). However, the reverse is not true.
It is possible that anything which is true of \(a\) is also true of \(b\), yet for \(a\) and \(b\) still to have different referents. This may seem puzzling, but it is easy to construct a model that shows this. Consider this model:
UD = {Rosencrantz, Guildenstern}
referent(\(a\)) = Rosencrantz
referent(\(b\)) = Guildenstern
for all predicates \(\mathcal{P}\), extension(\(\mathcal{P}\)) = ∅
extension(=) = {<Rosencrantz, Rosencrantz>,
<Guildenstern, Guildenstern>}
This specifies an extension for every predicate of QL: All the infinitely-many predicates are empty. This means that both \(Aa\) and \(Ab\) are false, and they are equivalent; both \(Ba\) and \(Bb\) are false; and so on for any two sentences that contain \(a\) and \(b\). Yet \(a\) and \(b\) refer to different things. We have written out the extension of identity to make this clear: The ordered pairhreferent(\(a\)),referent(\(b\))i is not in it. In this model, \(a\) = \(b\) is false and \(a\) ≠ \(b\) is true.


12.3: Important and Useful Rules/Formulas
Exponents (Assume each expression is defined.)
\(a^na^m = a^{n + m}\)
\(\dfrac{a^n}{a^m} = a^{n - m}\)
\((a^n)^m = a^{nm}\)
\((ab)^n = a^nb^n\)
\(a^{-1} = \dfrac{1}{n}\)
\(a^{-n} = \dfrac{1}{a^n}\)
\(a^0 = 1\)
\((\dfrac{a}{b})^n = \dfrac{a^n}{b^n}\)
Factorization and special product formulas
\(ab + ac = a(b + c)\)
\(a^2 + 2a +b^2 = (a+b)^2\)
\(a^2 - b^2 = (a + b)(a - b)\)
\(a^2 - 2ab + b^2 = (a-b)^2\)
Formulas
\(\begin{array}{flushleft}
x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a} & \text{ Quadratic formula}\\
y = mx + b & \text{ Slope-intercept form of a straight line}\\
y - y_1 = m(x - x_1) & \text{ Point-slope form of a straight line}\\
m = \dfrac{y_2 - y_1}{x_2 - x_1} & \text{ Slope of a straight line passing through the points } (x_1, x_2) \text{ and } (y_1, y_2)
\end{array}\)


11.9: Remaining Professional When You’re Frustrated
- Discuss ways to remain professional when you are feeling frustrated with others or a situation.
Behaving in a professional manner is a key to success in the workplace. Maintaining that demeanor, even in stressful times, can be a challenge. What does it mean to be “professional” at work? The definition varies, but usually includes possessing knowledge and expertise, being in a positive mood, meeting your obligations accurately and on time, respecting all with whom you interact, using proper language, operating ethically, having social and emotional intelligence and maintaining an appropriate appearance. Other terms describing professional conduct in the workplace are soft skills, protocol, business etiquette and polish.
Here is a video with some good advice on professional work characteristics:
At one point or another, we have all been subjected to negative circumstances and situations in the workplace that can test the patience of even the most professional of us. We are human beings. Our professional demeanor can temporarily be dented—engaging fight or flight mode, berating yourself, and lacking clear thinking can occur. The key is to rely on our emotional intelligence to gauge our thoughts and actions during these trying times.
Here are some techniques that can help you deal with emotional reactions to negative situations at work.
- Acceptance. It is normal to get mad when things go awry. Our brains are hard-wired to react in certain ways. It is best to step back and acknowledge that your emotions are normal so that you can move on to problem solving.
- Displacement. While you are experiencing a range of emotions that you may not initially control, it may be best for a change of scenery. Get up from your desk, walk out of your office and take some deep breaths outside. Imagine how you would like to see yourself react while you calm down.
- Articulation. Once you have spent some time thinking things through, it may be time to talk it out with the source of the issue. Remember your basic communication skills: Remember who you are communicating with and what will be effective in reaching them with your point.
- Improvement. After recognizing and dealing with your feelings, it is time to understand the true source of the issue so it can be solved going forward. So you were called out on some errors made in your analysis, but you know that you were not given adequate notice to properly prepare the report and double-check it. Address this with your manager and request an appropriate process in the future to allow for more careful work. [1]
Contributors and Attributions
- Remaining Professional When You're Frustrated. Authored by : Robert Danielson. Provided by : Lumen Learning. License : CC BY: Attribution
- 6 Traits of a True Professional. Authored by : MindToolsVideos. Located at : https://www.youtube.com/watch?v=2vFdQY1qSlM . License : All Rights Reserved . License Terms : Standard YouTube License


6.1: Organizing the Idea
By this point a speaker has chosen a topic, analyzed the audience, and gathered research on the subject. Now he or she must organize the information. Remember, public speakers should not try to memorize their speeches or improvise what they say, but speak extemporaneously. Compose a plan for what to say, then learn that plan, creating notes to keep on track, and then speak conversationally according to the plan.
To illustrate this point, take a look at the following example. Estimate much time it would take to memorize and repeat the following 41 letters:
y-m-s-e-c-p-h-e-i-s-a-u-t-o-b-m-u-s-o-a-t-e-p-o-r-x-e-e-n-n-o-r-o-t-a-a-i-n-i-z-g
Without a photographic memory, memorizing this seemingly random string of letters may prove nearly impossible. But what if the dashes got eliminated and letters reorganized as follows:
Notice that none of the letters changed; nothing got added or deleted. By arranging the letters into meaningful and manageable chunks, the message became more focused. The same holds true for information within a speech, whether speaking for 5 or 50 minutes. Besides the benefit associated with recalling information at will, a well-organized speech makes it easier for an audience to understand and recall the information shared, which is, of course, the end goal for an effective communicator.
Audiences can quickly tell the difference between an organized and a disorganized speaker. Disorganized speakers often bounce between unrelated points, detour into irrelevant stories, lose their connection to the audience, and generally seem unprepared. Such disorganization, at best, turns away an audience’s collective attention span, and at worst, can create a hostile, irritated, or insulted group of listeners. This does not suggest that a little disorganization will lead to failure, however. When a speaker can still engage, entertain, and inform effectively, a hint of disorganization may almost seem welcome, as it makes the speaker seem more fluid and conversational. On the whole though, audiences perceive organized speakers as more knowledgeable, articulate, and believable, ultimately gaining the their trust and respect.
To organize information efficiently, use the process of outlining to arrange the ideas for the speech. Outlines help speakers arrange the larger ideas into a manageable order, but then also help them fill in those larger ideas with supporting information to help expand and refine the major talking points. Outlines also help to ensure that both the introduction and conclusion effectively frame those larger ideas into a memorable format for the audience. The remainder of this chapter will present the recommended outline format needed to create effective speeches. First this chapter will cover the importance of introductions, followed by instructions on how to create the body of the speech, and end with a discussion on how to compose memorable conclusions.
Note to Self
Home Why Not Memorize?
Most novice speakers operate under the assumption that they should memorize their speeches, word-for-word, but that could not be further from the truth. The best speakers do not memorize, but rather learn their speeches in a process similar to learning directions from home to somewhere unfamiliar. Rather that obtaining a map and memorizing step-by-step, turn-by-turn directions, individuals pull up a map and learn the major milestones they need to note. They figure out where to turn, roughly how far to go between turns, and what to look for along the way. As such, an outline acts as a roadmap that focuses on the highlights that provide just enough detail to get from start to finish. Save the memorization for theatrical or cinematic performances.
Note To Self
In another analogy, think of a familiar story from your past, like when you learned to ride a bike. Could you tell the story without creating an outline and note cards? Of course you could, since you know the story. You might tell it differently from one retelling to the next, but the highlights of the story (the main points, central idea, etc.) remain the same.
Similar to a written essay or composition, speakers should utilize three main sections in an informative speech: the introduction, the body, and the conclusion. Each section serves an important purpose in crafting a memorable speech.
These three sections align perfectly with a saying often credited to Dale Carnegie : “Tell them what you are going to tell them, tell them, then tell them what you told them.” Though some question whether or not he coined the phrase, no such rift exists on the message it espouses, as a broad consensus among communication professionals and educators believe these three things represent all a person needs to know to craft a memorable speech or presentation regardless of length and complexity.
Tell Them What You Are Going to Tell Them
This portion serves as the introduction of the speech—the opening component that serves to engage the audience and capture their attention. The introduction has several specific roles to fill and generally should not consist of more than 10–15% of the speech. The introduction not only includes “coming attractions” for the audience, but it also grabs their attention and gives them a reason to sit up and pay attention.
Tell Them
This portion represents the substance or content of the speech. Organize this section into the most important points that will most clearly and effectively deliver the message to the audience. Provide the details of the speech, which should include researched information supported by evidence. This section of the speech should consume 70–80% of the speaking time.
Tell Them W hat You Told Them
Reiterate, summarize, and add punctuation during the speech’s conclusion. Like the introduction, the conclusion of the speech should only last 10–15% of the total time of delivery, but it serves as a critical role in achieving highly effective results. Reminding the audience about the most important points detailed in the body and ending the speech with a memorable closing statement solidifies the message in the minds of the audience. Abruptly ending a speech will nearly guarantee that the audience will remember less of it and for a shorter period of time—if at all.


1.1: Prelude to Prerequisites
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It’s a cold day in Antarctica. In fact, it’s always a cold day in Antarctica. Earth’s southernmost continent, Antarctica experiences the coldest, driest, and windiest conditions known. The coldest temperature ever recorded, over one hundred degrees below zero on the Celsius scale, was recorded by remote satellite. It is no surprise then, that no native human population can survive the harsh conditions. Only explorers and scientists brave the environment for any length of time.
Measuring and recording the characteristics of weather conditions in in Antarctica requires a use of different kinds of numbers. Calculating with them and using them to make predictions requires an understanding of relationships among numbers. In this chapter, we will review sets of numbers and properties of operations used to manipulate numbers. This understanding will serve as prerequisite knowledge throughout our study of algebra and trigonometry.


7.4: Crystal Structures of Metals
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The Crystalline Nature of Metals
All metallic elements (except Cs, Ga, and Hg) are crystalline solids at room temperature. Like ionic solids, metals and alloys have a very strong tendency to crystallize, whether they are made by thermal processing or by other techniques such as solution reduction or electroplating. Metals crystallize readily and it is difficult to form a glassy metal even with very rapid cooling. Molten metals have low viscosity, and the identical (essentially spherical) atoms can pack into a crystal very easily. Glassy metals can be made, however, by rapidly cooling alloys, particularly if the constituent atoms have different sizes. The different atoms cannot pack in a simple unit cell, sometimes making crystallization slow enough to form a glass.
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Body-centered cubic |
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hcp (left) and fcc (right) close-packing of spheres |
Crystal structures
Most metals and alloys crystallize in one of three very common structures: body-centered cubic (bcc), hexagonal close packed (hcp), or cubic close packed (ccp, also called face centered cubic, fcc). In all three structures the coordination number of the metal atoms (i.e., the number of equidistant nearest neighbors) is rather high: 8 for bcc, and 12 for hcp and ccp. We can contrast this with the low coordination numbers (i.e., low valences - like 2 for O, 3 for N, or 4 for C) found in nonmetals. In the bcc structure, the nearest neighbors are at the corners of a cube surrounding the metal atom in the center. In the hcp and ccp structures, the atoms pack like stacked cannonballs or billiard balls, in layers with a six-coordinate arrangement. Each atom also has six more nearest neighbors from layers above and below. The stacking sequence is ABCABC... in the ccp lattice and ABAB... in hcp. In both cases, it can be shown that the spheres fill 74% of the volume of the lattice. This is the highest volume fraction that can be filled with a lattice of equal spheres.
Atoms in metallic crystals have a tendency to pack in dense arrangments that fill space efficiently. The simple square packing (above) upon which the simple cubic structure is based is inefficient and thus rare among metallic crystal structures. Body- or face-centered structures fill space more efficiently and more common.
Periodic trends in structure and metallic behavior
Remember where we find the metallic elements in the periodic table - everywhere except the upper right corner. This means that as we go down a group in the p-block (let's say, group IVA, the carbon group, or group VA, the nitrogen group), the properties of the elements gradually change from nonmetals to metalloids to metals. The carbon group nicely illustrates the transition. Starting at the top, the element carbon has two stable allotropes - graphite and diamond. In each one, the valence of carbon atoms is exactly satisfied by making four electron pair bonds to neighboring atoms. In graphite, each carbon has three nearest neighbors, and so there are two single bonds and one double bond. In diamond, there are four nearest neighbors situated at the vertices of a tetrahedron, and so there is a single bond to each one.
The two elements right under carbon (silicon and germanium) in the periodic table also have the diamond structure (recall that these elements cannot make double bonds to themselves easily, so there is no graphite allotrope for Si or Ge). While diamond is a good insulator, both silicon and germanium are semiconductors (i.e., metalloids). Mechanically, they are hard like diamond. Like carbon, each atom of Si and Ge satisfies its valence of four by making single bonds to four nearest neighbors.
The next element under germanium is tin (Sn). Tin has two allotropes, one with the diamond structure, and one with a slightly distorted bcc structure. The latter has metallic properties (metallic luster, malleability), and conductivity about 10 9 times higher than Si. Finally, lead (Pb), the element under Sn, has the ccp structure, and also is metallic. Note the trends in coordination number and conducting properties:
| Element | Structure | Coord. no. | Conductivity |
|---|---|---|---|
| C | graphite, diamond | 3, 4 | semimetal, insulator |
| Si | diamond | 4 | semiconductor |
| Ge | diamond | 4 | semiconductor |
| Sn | diamond, distorted bcc | 4, 8 | semiconductor, metal |
| Pb | ccp | 12 | metal |
The elements C, Si, and Ge obey the octet rule, and we can easily identify the electron pair bonds in their structures. Sn and Pb, on the other hand, adopt structures with high coordination numbers. They do not have enough valence electrons to make electron pair bonds to each neighbor (this is a common feature of metals). What happens in this case is that the valence electrons become "smeared out" or delocalized over all the atoms in the crystal. It is best to think of the bonding in metals as a crystalline arrangement of positively charged cores with a "sea" of shared valence electrons gluing the structure together. Because the electrons are not localized in any particular bond between atoms, they can move in an electric field, which is why metals conduct electricity well. Another way to describe the bonding in metals is nondirectional. That is, an atom's nearest neighbors surround it in every direction, rather than in a few particular directions (like at the corners of a tetrahedron, as we found for diamond). Nonmetals (insulators and semiconductors), on the other hand, have directional bonding. Because the bonding is non-directional and coordination numbers are high, it is relatively easy to deform the coordination sphere (i.e., break or stretch bonds) than it is in the case of a nonmetal. This is why elements like Pb are much more malleable than C, Si, or Ge.


2.1: Reference Material
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This chapter was edited by Lauren Brand, with content contributions by Lauren Brand, Carole Butcher, Josh Garrett-Davis, Tracey Hanshew, Nick Roland, David Schley, Emma Teitelman, and Alyce Webb.
Recommended citation: Lauren Brand et al., “Conquering the West,” Lauren Brand, ed., in The American Yawp , eds. Joseph Locke and Ben Wright (Stanford, CA: Stanford University Press, 2018).
Recommended Reading
- Aarim, Najia. Chinese Immigrants, African Americans, and Racial Anxiety in the United States, 1848–1882. Champaign: University of Illinois Press, 2006.
- Andrews, Thomas. Killing for Coal: America’s Deadliest Labor War. Cambridge, MA: Harvard University Press, 2009.
- Brown, Dee. Bury My Heart at Wounded Knee: An Indian History of the American West. New York: Holt, Rinehart and Winston, 1970.
- Cahill, Cathleen. Federal Fathers and Mothers: A Social History of the United States Indian Service, 1869–1933. Chapel Hill: University of North Carolina Press, 2011.
- Cronon, William. Nature’s Metropolis: Chicago and the Great West. New York: Norton, 1991.
- Gordan, Linda. The Great Arizona Orphan Abduction. Cambridge, MA: Harvard University Press, 1999.
- Hämäläinen, Pekka. The Comanche Empire. New Haven, CT: Yale University Press, 2008.
- Hine, Robert V. The American West: A New Interpretive History. New Haven, CT: Yale University Press, 2000.
- Huhndorf, Shari M. Going Native: Indians in the American Cultural Imagination. Ithaca, NY: Cornell University Press, 2001.
- Isenberg, Andrew C. The Destruction of the Bison: An Environmental History, 1750–1920. Cambridge, UK: Cambridge University Press, 2000.
- Jacobs, Margaret D. White Mother to a Dark Race: Settler Colonialism, Maternalism, and the Removal of Indigenous Children in the American West and Australia, 1880–1940. Lincoln: University of Nebraska Press, 2009.
- Johnson, Benjamin Heber. Revolution in Texas: How a Forgotten Rebellion and Its Bloody Suppression Turned Mexicans into Americans. New Haven, CT: Yale University Press, 2003.
- Kelman, Ari. A Misplaced Massacre: Struggling over the Memory of Sand Creek. Cambridge, MA: Harvard University Press, 2013.
- Krech, Shepard. The Ecological Indian: Myth and History. New York: Norton, 1999.
- Limerick, Patricia Nelson. The Legacy of Conquest: The Unbroken Past of the American West. New York: Norton, 1987.
- Marks, Paula Mitchell. In a Barren Land: American Indian Dispossession and Survival. New York: Morrow, 1998.
- Montejano, David. Anglos and Mexicans in the Making of Texas, 1836–1986. Austin: University of Texas Press, 1987.
- Pascoe, Peggy. Relations of Rescue: The Search for Female Moral Authority in the American West, 1874–1939. New York: Oxford University Press, 1990.
- Prucha, Francis Paul. The Great Father: The United States Government and the American Indians. Lincoln: University of Nebraska Press, 1984.
- Schulten, Susan. The Geographical Imagination in America, 1880–1950. Chicago: University of Chicago Press, 2001.
- Shah, Nayan. Stranger Intimacy: Contesting Race, Sexuality, and the Law in the North American West. Berkeley: University of California Press, 2011.
- Smith, Henry Nash. Virgin Land: The American West as Symbol and Myth. New York: Vintage Books, 1957.
- Taylor, Quintard. In Search of the Racial Frontier: African Americans in the American West, 1528–1990. New York: Norton, 1999.
- Warren, Louis S. Buffalo Bill’s America: William Cody and the Wild West Show. New York: Knopf, 2005.
- White, Richard. “It’s Your Misfortune and None of My Own”: A New History of the American West. Norman: University of Oklahoma Press, 1991.
Notes
- Based on U.S. Census figures from 1900. See, for instance, Donald Lee Parman, Indians and the American West in the Twentieth Century (Bloomington: Indiana University Press, 1994), ix.
- Rodman W. Paul, The Mining Frontiers of the West, 1848–1880 (New York: Holt, Rinehart and Winston, 1963); Richard Lingenfelter, The Hard Rock Miners (Berkeley: University of California Press, 1979).
- Richard White, It’s Your Misfortune and None of My Own: A New History of the American West (Norman: University of Oklahoma Press, 1991), 216–220.
- Matthew Bowman, The Mormon People: The Making of an American Faith (New York: Random House, 2012).
- White, It’s Your Misfortune , 142–148; Patricia Nelson Limerick, The Legacy of Conquest: The Unbroken Past of the American West (New York: Norton, 1987), 161–162
- White, It’s Your Misfortune; Limerick, Legacy of Conquest .
- John D. Hicks, The Populist Revolt: A History of the Farmers’ Alliance and the People’s Party (Minneapolis: University of Minnesota Press, 1931), 6.
- Robert Utley, The Indian Frontier 1846–1890 (Albuquerque: University of New Mexico Press, 1984), 76.
- Jeffrey Ostler, The Plains Sioux and U.S. Colonialism from Lewis and Clark to Wounded Knee (New York: Cambridge University Press, 2004).
- Elliott West, The Contested Plains: Indians, Goldseekers, and the Rush to Colorado (Lawrence: Kansas University Press, 1998.
- Francis Paul Prucha, The Great Father: The United States Government and the American Indians (Lincoln: University of Nebraska Press, 1995), 482.
- Bureau of Indian Affairs, Annual Report of the Commissioner of Indian Affairs to the Secretary of the Interior (Washington, DC: U.S. Government Printing Office, 1875), 221.
- For the Comanche, see especially Pekka Hämäläinen, The Comanche Empire (New Haven, CT: Yale University Press, 2008)
- Ostler, The Plains Sioux and U.S. Colonialism .
- Utley, The Indian Frontier .
- Boyd Cothran, Remembering the Modoc War: Redemptive Violence and the Making of American Innocence (Chapel Hill: University of North Carolina Press, 2014).
- Report of the Secretary of War, Being Part of the Message and Documents Communicated to the Two Houses of Congress, Beginning of the Second Session of the Forty-Fifth Congress. Volume I (Washington, DC: U.S. Government Printing Office 1877), 630.
- Alfred D. Chandler Jr. The Visible Hand: The Managerial Revolution in American Business (Cambridge, MA: Belknap Press, 1977).
- Richard White, Railroaded: The Transcontinentals and the Making of Modern America (New York: Norton, 2011), 107.
- Walter Licht, Working on the Railroad: The Organization of Work in the Nineteenth Century (Princeton, NJ: Princeton University Press, 2014), chap. 5.
- John F. Stover, The Routledge Historical Atlas of the American Railroads (New York: Routledge, 1999), 15, 17, 39, 49.
- Richard W. Slatta, Cowboys of the Americas (New Haven, CT: Yale University Press, 1994). Richard W. Slatta, Cowboys of the Americas (New Haven, CT: Yale University Press, 1994).
- Limerick, Legacy of Conquest , 195–199; White, It’s Your Misfortune , 115
- Dee Brown, Bury My Heart at Wounded Knee: An Indian History of the American West (New York: Holt, Rinehart and Winston, 1970).
- Joy S. Kasson, Buffalo Bill’s Wild West: Celebrity, Memory, and Popular History (New York: Macmillan, 2001).
- Frederick Jackson Turner, The Frontier in American History (New York: Holt, 1921), 12.
- Kasson, Buffalo Bill’s Wild West , 117.


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14.10: Nervous System (Summary)
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The
neuron
is the basic unit of the nervous system. It consists of a
cell body
with a nucleus, filaments known as
dendrites
and a long fibre known as the
axon
often surrounded by a
myelin sheath
.
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A
nerve
is a bundle of axons.

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Nerve Impulses
travel along axons.
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Adjacent neurons connect with each other at
synapses
.
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Reflexes
are automatic responses to stimuli. The path taken by nerve impulses involved in reflexes is a
reflex arc
. Most reflex arcs involve 3 neurons - a
sensory neuron
, a
relay neuron
and a
motor neuron
. A stimulus, a pin in the paw for example, initiates an impulse in the sensory neuron that passes via a synapse to the relay neuron situated in the spinal cord and then via another synapse to the motor neurone. This transmits the impulse to the muscle causing it to contract and remove the paw from the pin.
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The nervous system is divided into 2 parts: the
central nervous system
, consisting of the brain and spinal cord and the
peripheral nervous
system
consisting of nerves connected to the brain and spinal cord. The
autonomic nervous system
is considered to be part of the peripheral nervous system.
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The brain consists of three major regions: 1. the
fore brain
which includes the
cerebral hemispheres
(or
cerebrum
),
hypothalamus
and
pituitary gland
; 2. the
hindbrain
or
brain stem
containing the
medulla oblongata
and 3. the
cerebellum
.
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Protective membranes known as the
meninges
surround the brain and spinal cord.
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There are 12 pairs of cranial nerves that include the optic, olfactory, acoustic and
vagus
nerves.
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The
spinal cord
is a cable of nerve tissue surrounded by meninges passing from the brain to the end of the tail.
Spinal nerves
emerge by a
ventral
and
dorsal root
between each vertebra and connect the spinal cord with organs and muscles.
-
The
autonomic nervous system
controls internal body functions not under conscious control. It is divided into 2 parts with 2 different functions: the
sympathetic nervous system
that is involved in the flight and fight response including increased heart rate, bronchial dilation, dilation of the pupil and decreased gut activity. The
parasympathetic nervous system
is associated with decreased heart rate, pupil constriction and increased gut activity.


7.1: Abstract
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The phrase ‘form follows function’, originally conceived as an aesthetic principle, has been applied to fields as disparate as architecture and software engineering. I use it here as a starting point from which to unpick the complex and changing relationship between writing and its supports during the Aegean Bronze Age, with the basic hypothesis that the shape, and to a lesser extent, material, of objects that bear writing change according to the purpose to which they, object + writing, are put. I examine the evidence at two levels. Firstly, the use of writing supports in each of the three main Aegean scripts, Cretan Hieroglyphic, Linear A. and Linear B, is reviewed. Cretan Hieroglyphic and Linear A are both in use on Crete during the First and early Second Palace Periods, although largely in different areas, offering the possibility of comparing contemporary approaches to the creation and use of different objects on which to write what seem to be (given that both scripts are undeciphered) broadly similar subject matters. Cretan Hieroglyphic ceases to be used later in the Second Palace Period, and Linear A use spreads — likewise, Linear B replaces Linear A in the Third Palace Period; these two transitions allow us to look at how practice changes through time, but also, potentially, at the deliberate refinement of writing supports as certain forms are carried from old to new script, new shapes are introduced, and others go out of use. While keeping these longer term patterns in mind, I then focus on Linear A; its diverse range of writing supports offers the potential of building up a more detailed picture of how and where different kinds of writing-bearing object are used within a particular chronological period. Writing appears on objects we classify as administrative, such as clay tablets, but also, intriguingly, on what seem to be non-administrative items like metal pins or stone ‘libation tables’, giving the impression of a loose and flexible attitude to what can be written upon. Key questions to consider include to what extent this diversity of shape is ‘organised’? Does the shape of the writing support add meaning to the usually brief inscription, or vice versa? And, is it possible that people interacting with writing might have visibility of only one kind of support — what would this mean for their conception of writing, and our definitions of literacy? To conclude, I return to the longer view, and my original hypothesis, to consider whether form really does follow function with Aegean Bronze Age writing, and whether the changes that occur result from writing-users refining the system, or the system refining the users.
How to cite this book chapter:
Finlayson, S. 2013. Form Follows Function: Writing and its supports in the Aegean Bronze Age. In: Piquette, K. E. and Whitehouse, R. D. (eds.)
Writing as Material Practice: Substance, surface and medium.
Pp. 123-142. London: Ubiquity Press. DOI:
http://dx.doi.org/10.5334/bai.g


1.6: Dispersion
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Learning Objectives
By the end of this section, you will be able to:
- Explain the cause of dispersion in a prism
- Describe the effects of dispersion in producing rainbows
- Summarize the advantages and disadvantages of dispersion
Everyone enjoys the spectacle of a rainbow glimmering against a dark stormy sky. How does sunlight falling on clear drops of rain get broken into the rainbow of colors we see? The same process causes white light to be broken into colors by a clear glass prism or a diamond (Figure \(\PageIndex{1}\)).
We see about six colors in a rainbow—red, orange, yellow, green, blue, and violet; sometimes indigo is listed, too. These colors are associated with different wavelengths of light, as shown in Figure \(\PageIndex{2}\). When our eye receives pure-wavelength light, we tend to see only one of the six colors, depending on wavelength. The thousands of other hues we can sense in other situations are our eye’s response to various mixtures of wavelengths. White light, in particular, is a fairly uniform mixture of all visible wavelengths. Sunlight, considered to be white, actually appears to be a bit yellow, because of its mixture of wavelengths, but it does contain all visible wavelengths. The sequence of colors in rainbows is the same sequence as the colors shown in the figure. This implies that white light is spread out in a rainbow according to wavelength. Dispersion is defined as the spreading of white light into its full spectrum of wavelengths. More technically, dispersion occurs whenever the propagation of light depends on wavelength.
Any type of wave can exhibit dispersion. For example, sound waves, all types of electromagnetic waves, and water waves can be dispersed according to wavelength. Dispersion may require special circumstances and can result in spectacular displays such as in the production of a rainbow. This is also true for sound, since all frequencies ordinarily travel at the same speed. If you listen to sound through a long tube, such as a vacuum cleaner hose, you can easily hear it dispersed by interaction with the tube. Dispersion, in fact, can reveal a great deal about what the wave has encountered that disperses its wavelengths. The dispersion of electromagnetic radiation from outer space, for example, has revealed much about what exists between the stars—the so-called interstellar medium.
Nick Moore’s video discusses dispersion of a pulse as he taps a long spring. Follow his explanation as Moore replays the high-speed footage showing high frequency waves outrunning the lower frequency waves. https://www.youtube.com/watch?v=KbmOcT5sX7I
Refraction is responsible for dispersion in rainbows and many other situations. The angle of refraction depends on the index of refraction, as we know from Snell’s law. We know that the index of refraction n depends on the medium. But for a given medium, n also depends on wavelength (Table \(\PageIndex{1}\)).
| Medium | Red (660 nm) | Orange (610 nm) | Yellow (580 nm) | Green (550 nm) | Blue (470 nm) | Violet (410 nm) |
|---|---|---|---|---|---|---|
| Water | 1.331 | 1.332 | 1.333 | 1.335 | 1.338 | 1.342 |
| Diamond | 2.410 | 2.415 | 2.417 | 2.426 | 2.444 | 2.458 |
| Glass, crown | 1.512 | 1.514 | 1.518 | 1.519 | 1.524 | 1.530 |
| Glass, flint | 1.662 | 1.665 | 1.667 | 1.674 | 1.684 | 1.698 |
| Polystyrene | 1.488 | 1.490 | 1.492 | 1.493 | 1.499 | 1.506 |
| Quartz, fused | 1.455 | 1.456 | 1.458 | 1.459 | 1.462 | 1.468 |
Note that for a given medium, n increases as wavelength decreases and is greatest for violet light. Thus, violet light is bent more than red light, as shown for a prism in Figure \(\PageIndex{3b}\). White light is dispersed into the same sequence of wavelengths as seen in Figures \(\PageIndex{1}\) and \(\PageIndex{2}\).
Example \(\PageIndex{1}\): Dispersion of White Light by Flint Glass
A beam of white light goes from air into flint glass at an incidence angle of 43.2°. What is the angle between the red (660 nm) and violet (410 nm) parts of the refracted light?
Strategy
Values for the indices of refraction for flint glass at various wavelengths are listed in Table \(\PageIndex{1}\). Use these values for calculate the angle of refraction for each color and then take the difference to find the dispersion angle.
Solution
Applying the law of refraction for the red part of the beam
\[n_{air}\sin θ_{air}=n_{red} \sinθ_{red}, \nonumber \]
we can solve for the angle of refraction as
\[θ_{red}=\sin^{−1}(\frac{n_{air}\sin θ_{air}}{n_{red}})=\sin^{−1}[\frac{(1.000)\sin43.2°}{(1.512)}]=27.0°. \nonumber \]
Similarly, the angle of incidence for the violet part of the beam is
\[θ_{violet}=\sin^{−1}(\frac{n_{air}sinθ_{air}}{n_{violet}})=\sin^{−1}[\frac{(1.000)\sin43.2°}{(1.530)}]=26.4°. \nonumber \]
The difference between these two angles is
\[θ_{red}−θ_{violet}=27.0°−26.4°=0.6°. \nonumber \]
Significance
Although 0.6° may seem like a negligibly small angle, if this beam is allowed to propagate a long enough distance, the dispersion of colors becomes quite noticeable.
Exercise \(\PageIndex{1}\)
In the preceding example, how much distance inside the block of flint glass would the red and the violet rays have to progress before they are separated by 1.0 mm?
- Answer
-
9.3 cm
Rainbows are produced by a combination of refraction and reflection. You may have noticed that you see a rainbow only when you look away from the Sun. Light enters a drop of water and is reflected from the back of the drop (Figure \(\PageIndex{4}\)).
The light is refracted both as it enters and as it leaves the drop. Since the index of refraction of water varies with wavelength, the light is dispersed, and a rainbow is observed (Figure \(\PageIndex{4a}\)). (No dispersion occurs at the back surface, because the law of reflection does not depend on wavelength.) The actual rainbow of colors seen by an observer depends on the myriad rays being refracted and reflected toward the observer’s eyes from numerous drops of water. The effect is most spectacular when the background is dark, as in stormy weather, but can also be observed in waterfalls and lawn sprinklers. The arc of a rainbow comes from the need to be looking at a specific angle relative to the direction of the Sun, as illustrated in Figure \(\PageIndex{4b}\). If two reflections of light occur within the water drop, another “secondary” rainbow is produced. This rare event produces an arc that lies above the primary rainbow arc, as in Figure \(\PageIndex{4c}\), and produces colors in the reverse order of the primary rainbow, with red at the lowest angle and violet at the largest angle.
Dispersion may produce beautiful rainbows, but it can cause problems in optical systems. White light used to transmit messages in a fiber is dispersed, spreading out in time and eventually overlapping with other messages. Since a laser produces a nearly pure wavelength, its light experiences little dispersion, an advantage over white light for transmission of information. In contrast, dispersion of electromagnetic waves coming to us from outer space can be used to determine the amount of matter they pass through.


4.3: The Seasons
By the end of this section, you will be able to:
- Describe how the tilt of Earth’s axis causes the seasons
- Explain how seasonal differences on Earth vary with latitude
One of the fundamental facts of life at Earth’s midlatitudes, where most of this book’s readers live, is that there are significant variations in the heat we receive from the Sun during the course of the year. We thus divide the year into seasons , each with its different amount of sunlight. The difference between seasons gets more pronounced the farther north or south from the equator we travel, and the seasons in the Southern Hemisphere are the opposite of what we find on the northern half of Earth. With these observed facts in mind, let us ask what causes the seasons.
Many people have believed that the seasons were the result of the changing distance between Earth and the Sun. This sounds reasonable at first: it should be colder when Earth is farther from the Sun. But the facts don’t bear out this hypothesis. Although Earth’s orbit around the Sun is an ellipse, its distance from the Sun varies by only about 3%. That’s not enough to cause significant variations in the Sun’s heating. To make matters worse for people in North America who hold this hypothesis, Earth is actually closest to the Sun in January, when the Northern Hemisphere is in the middle of winter. And if distance were the governing factor, why would the two hemispheres have opposite seasons? As we shall show, the seasons are actually caused by the 23.5° tilt of Earth’s axis.
The Seasons and Sunshine
Figure 4.5 shows Earth’s annual path around the Sun , with Earth’s axis tilted by 23.5°. Note that our axis continues to point the same direction in the sky throughout the year. As Earth travels around the Sun, in June the Northern Hemisphere “leans into” the Sun and is more directly illuminated. In December, the situation is reversed: the Southern Hemisphere leans into the Sun, and the Northern Hemisphere leans away. In September and March, Earth leans “sideways”—neither into the Sun nor away from it—so the two hemispheres are equally favored with sunshine.
How does the Sun’s favoring one hemisphere translate into making it warmer for us down on the surface of Earth? There are two effects we need to consider. When we lean into the Sun, sunlight hits us at a more direct angle and is more effective at heating Earth’s surface (Figure 4.6). You can get a similar effect by shining a flashlight onto a wall. If you shine the flashlight straight on, you get an intense spot of light on the wall. But if you hold the flashlight at an angle (if the wall “leans out” of the beam), then the spot of light is more spread out. Like the straight-on light, the sunlight in June is more direct and intense in the Northern Hemisphere, and hence more effective at heating.
The second effect has to do with the length of time the Sun spends above the horizon (Figure 4.7). Even if you’ve never thought about astronomy before, we’re sure you have observed that the hours of daylight increase in summer and decrease in winter. Let’s see why this happens.
As we saw in Observing the Sky: The Birth of Astronomy, an equivalent way to look at our path around the Sun each year is to pretend that the Sun moves around Earth (on a circle called the ecliptic). Because Earth’s axis is tilted, the ecliptic is tilted by about 23.5° relative to the celestial equator (review Figure 2.7). As a result, where we see the Sun in the sky changes as the year wears on.
In June, the Sun is north of the celestial equator and spends more time with those who live in the Northern Hemisphere. It rises high in the sky and is above the horizon in the United States for as long as 15 hours. Thus, the Sun not only heats us with more direct rays, but it also has more time to do it each day. (Notice in Figure 4.7 that the Northern Hemisphere’s gain is the Southern Hemisphere’s loss. There the June Sun is low in the sky, meaning fewer daylight hours. In Chile, for example, June is a colder, darker time of year.) In December, when the Sun is south of the celestial equator, the situation is reversed.
The Motions of the Sun Simulator from Columbia University's Center for Teaching and Learning provides a demonstration of the Sun's apparent motion in the sky as the Earth rotates each day, and its changing altitude with latitude and time of year.
Let’s look at what the Sun’s illumination on Earth looks like at some specific dates of the year, when these effects are at their maximum. On or about June 21 (the date we who live in the Northern Hemisphere call the summer solstice or sometimes the first day of summer), the Sun shines down most directly upon the Northern Hemisphere of Earth. It appears about 23° north of the equator, and thus, on that date, it passes through the zenith of places on Earth that are at 23° N latitude. The situation is shown in detail in Figure 4.8. To a person at 23° N (near Hawaii, for example), the Sun is directly overhead at noon. This latitude, where the Sun can appear at the zenith at noon on the first day of summer, is called the Tropic of Cancer .
We also see in Figure 4.8 that the Sun’s rays shine down all around the North Pole at the solstice . As Earth turns on its axis, the North Pole is continuously illuminated by the Sun; all places within 23° of the pole have sunshine for 24 hours. The Sun is as far north on this date as it can get; thus, 90° – 23° (or 67° N) is the southernmost latitude where the Sun can be seen for a full 24-hour period (sometimes called the “land of the midnight Sun”). That circle of latitude is called the Arctic Circle .
Many early cultures scheduled special events around the summer solstice to celebrate the longest days and thank their gods for making the weather warm. This required people to keep track of the lengths of the days and the northward trek of the Sun in order to know the right day for the “party.” (You can do the same thing by watching for several weeks, from the same observation point, where the Sun rises or sets relative to a fixed landmark. In spring, the Sun will rise farther and farther north of east, and set farther and farther north of west, reaching the maximum around the summer solstice.)
Now look at the South Pole in Figure 4.8. On June 21, all places within 23° of the South Pole—that is, south of what we call the Antarctic Circle —do not see the Sun at all for 24 hours.
The situation is reversed 6 months later, about December 21 (the date of the winter solstice , or the first day of winter in the Northern Hemisphere), as shown in Figure 4.9. Now it is the Arctic Circle that has the 24-hour night and the Antarctic Circle that has the midnight Sun. At latitude 23° S, called the Tropic of Capricorn , the Sun passes through the zenith at noon. Days are longer in the Southern Hemisphere and shorter in the north. In the United States and Southern Europe, there may be only 9 or 10 hours of sunshine during the day. It is winter in the Northern Hemisphere and summer in the Southern Hemisphere.
As you can see in Figure 4.8, the Tropic of Cancer is the latitude for which the Sun is directly overhead on the summer solstice. At this time, the Sun is at a declination of 23° N of the celestial equator, and the corresponding latitude on Earth is 23° N of the equator. If Earth were tilted a bit less, then the Tropic of Cancer would be at a lower latitude, closer to the equator.
The Arctic Circle marks the southernmost latitude for which the day length is 24 hours on the day of the summer solstice. This is located at 90° – 23° = 67° N of Earth’s equator. If Earth were tilted a bit less, then the Arctic Circle would move farther North. In the limit at which Earth is not tilted at all (its axis is perpendicular to the ecliptic), the Tropic of Cancer would be right on Earth’s equator, and the Arctic Circle would simply be the North Pole. Suppose the tilt of Earth’s axis were tilted only 5°. What would be the effect on the seasons and the locations of the Tropic of Cancer and Arctic Circle?
Solution
If Earth were tilted less, the seasons would be less extreme. The variation in day length and direct sunlight would be very small over the course of a year, and the Sun’s daily path in the sky would not vary much. If Earth were tilted by 5°, the Sun’s position on the day of the summer solstice would be 5° N of the celestial equator, so the Tropic of Cancer would be at the corresponding latitude on Earth of 5° N of the Equator. The Arctic Circle would be located at 90° – 5° = 85° N of the equator.
Suppose the tilt of Earth’s axis were 16°. What, then, would be the difference in latitude between the Arctic Circle and the Tropic of Cancer? What would be the effect on the seasons compared with that produced by the actual tilt of 23°?
- Answer
-
The Tropic of Cancer is at a latitude equal to Earth’s tilt, so in this case, it would be at 16° N latitude. The Arctic Circle is at a latitude equal to 90° minus Earth’s tilt, or 90° – 16° = 74°. The difference between these two latitudes is 74° – 16° = 58°. Since the tilt of Earth is less, there would be less variation in the tilt of Earth and less variation in the Sun’s paths throughout the year, so there would be milder seasonal changes.
The Columbia University’s Center for Teaching and Learning’s Motions of the Sun Simulator allows you to see how the Sun’s changing altitude over the course of the year changes the intensity of lighting experienced on Earth. Select the “Step by day” option before running the animation to illustrate this effect.
Many cultures that developed some distance north of the equator have a celebration around December 21 to help people deal with the depressing lack of sunlight and the often dangerously cold temperatures. Originally, this was often a time for huddling with family and friends, for sharing the reserves of food and drink, and for rituals asking the gods to return the light and heat and turn the cycle of the seasons around. Many cultures constructed elaborate devices for anticipating when the shortest day of the year was coming. Stonehenge in England, built long before the invention of writing, is probably one such device. In our own time, we continue the winter solstice tradition with various holiday celebrations around that December date.
Halfway between the solstices, on about March 21 and September 21, the Sun is on the celestial equator. From Earth, it appears above our planet’s equator and favors neither hemisphere. Every place on Earth then receives roughly 12 hours of sunshine and 12 hours of night. The points where the Sun crosses the celestial equator are called the vernal (spring) and autumnal (fall) equinoxes .
The Seasons at Different Latitudes
The seasonal effects are different at different latitudes on Earth. Near the equator, for instance, all seasons are much the same. Every day of the year, the Sun is up half the time, so there are approximately 12 hours of sunshine and 12 hours of night. Local residents define the seasons by the amount of rain (wet season and dry season) rather than by the amount of sunlight. As we travel north or south, the seasons become more pronounced, until we reach extreme cases in the Arctic and Antarctic.
At the North Pole, all celestial objects that are north of the celestial equator are always above the horizon and, as Earth turns, circle around parallel to it. The Sun is north of the celestial equator from about March 21 to September 21, so at the North Pole, the Sun rises when it reaches the vernal equinox and sets when it reaches the autumnal equinox. Each year there are 6 months of sunshine at each pole, followed by 6 months of darkness.
The Sun’s coordinates on the celestial sphere range from a declination of 23° N of the celestial equator (or +23°) to a declination 23° S of the celestial equator (or –23°). So, the Sun’s altitude at noon, when it crosses the meridian, varies by a total of 46°. What is the altitude of the Sun at noon on March 21, as seen from a place on Earth’s equator? What is its altitude on June 21, as seen from a place on Earth’s equator?
Solution
On Earth’s equator, the celestial equator passes through the zenith. On March 21, the Sun is crossing the celestial equator, so it should be found at the zenith (90°) at noon. On June 21, the Sun is 23° N of the celestial equator, so it will be 23° away from the zenith at noon. The altitude above the horizon will be 23° less than the altitude of the zenith (90°), so it is 90° – 23° = 67° above the horizon.
What is the altitude of the Sun at noon on December 21, as seen from a place on the Tropic of Cancer?
- Answer
-
On the day of the winter solstice, the Sun is located about 23° S of the celestial equator. From the Tropic of Cancer, a latitude of 23° N, the zenith would be a declination of 23° N. The difference in declination between zenith and the position of the Sun is 46°, so the Sun would be 46° away from the zenith. That means it would be at an altitude of 90° – 46° = 44°.
Clarifications about the Real World
In our discussions so far, we have been describing the rising and setting of the Sun and stars as they would appear if Earth had little or no atmosphere. In reality, however, the atmosphere has the curious effect of allowing us to see a little way “over the horizon.” This effect is a result of refraction , the bending of light passing through air or water, something we will discuss in Astronomical Instruments. Because of this atmospheric refraction (and the fact that the Sun is not a point of light but a disk), the Sun appears to rise earlier and to set later than it would if no atmosphere were present.
In addition, the atmosphere scatters light and provides some twilight illumination even when the Sun is below the horizon. Astronomers define morning twilight as beginning when the Sun is 18° below the horizon, and evening twilight extends until the Sun sinks more than 18° below the horizon.
These atmospheric effects require small corrections in many of our statements about the seasons. At the equinoxes, for example, the Sun appears to be above the horizon for a few minutes longer than 12 hours, and below the horizon for fewer than 12 hours. These effects are most dramatic at Earth’s poles, where the Sun actually can be seen more than a week before it reaches the celestial equator.
You probably know that the summer solstice (June 21) is not the warmest day of the year, even if it is the longest. The hottest months in the Northern Hemisphere are July and August. This is because our weather involves the air and water covering Earth’s surface, and these large reservoirs do not heat up instantaneously. You have probably observed this effect for yourself; for example, a pond does not get warm the moment the Sun rises but is warmest late in the afternoon, after it has had time to absorb the Sun’s heat. In the same way, Earth gets warmer after it has had a chance to absorb the extra sunlight that is the Sun’s summer gift to us. And the coldest times of winter are a month or more after the winter solstice.
Footnotes
- 1 Note that the dates indicated for the solstices and equinoxes are approximate; depending on the year, they may occur a day or two earlier or later.