3.4: Kohlberg's Stages of Moral Development
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Lawrence Kohlberg (1963) built on the work of Piaget and was interested in finding out how our moral reasoning changes as we get older. He wanted to find out how people decide what is right and what is wrong. In order to explore this area, he read a story containing a moral dilemma to boys of different age groups. In the story, a man is trying to obtain an expensive drug that his wife needs in order to treat her cancer. The man has no money and no one will loan him the money he requires. He begs the pharmacist to reduce the price, but the pharmacist refuses. So, the man decides to break into the pharmacy to steal the drug. Then Kohlberg asked the children to decide whether the man was right or wrong in his choice. Kohlberg was not interested in whether they said the man was right or wrong, he was interested in finding out how they arrived at such a decision. He wanted to know what they thought made something right or wrong.
Pre-conventional Moral Development
The youngest subjects seemed to answer based on what would happen to the man as a result of the act. For example, they might say the man should not break into the pharmacy because the pharmacist might find him and beat him. Or they might say that the man should break in and steal the drug and his wife will give him a big kiss. Right or wrong, both decisions were based on what would physically happen to the man as a result of the act. This is a self-centered approach to moral decision-making. He called this most superficial understanding of right and wrong pre-conventional moral development.
Conventional Moral Development
Middle childhood boys seemed to base their answers on what other people would think of the man as a result of his act. For instance, they might say he should break into the store, and then everyone would think he was a good husband. Or, he shouldn’t because it is against the law. In either case, right and wrong is determined by what other people think. A good decision is one that gains the approval of others or one that complies with the law. This he called conventional moral development.
Post-conventional Moral Development
Older children were the only ones to appreciate the fact that this story has different levels of right and wrong. Right and wrong are based on social contracts established for the good of everyone or on universal principles of right and wrong that transcend the self and social convention. For example, the man should break into the store because, even if it is against the law, the wife needs the drug and her life is more important than the consequences the man might face for breaking the law. Or, the man should not violate the principle of the right of property because this rule is essential for social order. In either case, the person’s judgment goes beyond what happens to the self. It is based on a concern for others; for society as a whole or for an ethical standard rather than a legal standard. This level is called post-conventional moral development because it goes beyond convention or what other people think to a higher, universal ethical principle of conduct that may or may not be reflected in the law. Notice that such thinking (the kind supreme justices do all day in deliberating whether a law is moral or ethical, etc.) requires being able to think abstractly. Often this is not accomplished until a person reaches adolescence or adulthood.
Exercise:
Consider your own decision-making processes. What guides your decisions? Are you primarily concerned with your personal well-being? Do you make choices based on what other people will think about your decision? Or are you guided by other principles? To what extent is this approach guided by your culture?


6: Social Groups and Organization Last updated Save as PDF Page ID 130593 Anonymous LibreTexts 6.1: Society and Groups 6.2: Types of Social Groups 6.2A: The Nature of Groups 6.2B: Primary Groups 6.2C: Secondary Groups 6.2D: In-Groups and Out-Groups 6.2E: Reference Groups 6.2F: Social Networks 6.2G: Online Communities 6.3: Functions of Social Groups 6.3A: Defining Boundaries 6.3B: Choosing Leaders 6.3C: Making Decisions 6.3D: Setting Goals 6.3E: Controlling the Behaviors of Group Members 6.4: Large Social Groups 6.4A: Formal Structure 6.4B: Informal Structure 6.4C: Gemeinschaft and Gesellschaft 6.4D: Mechanical and Organic Solidarity 6.5: Bureaucracy 6.5A: Bureaucracies and Formal Groups 6.5B: Weber’s Model for Bureaucracy 6.5C: The “McDonaldization” of Society 6.6: Group Dynamics 6.6A: Effects of Group Size on Stability and Intimacy 6.6B: Effects of Group Size on Attitude and Behavior 6.6C: The Asch Experiment- The Power of Peer Pressure 6.6D: The Milgram Experiment- The Power of Authority 6.6E: Groupthink 6.7: Social Structure in the Global Perspective 6.7B: Gemeinschaft and Gesellschaft 6.7C: Lenski’s Sociological Evolution Approach


1.6: Samuel de Champlain (c. 1570–1635)
Samuel de Champlain was born at Brouage, Saintagone, France. His education focused on seamanship and navigation. In 1599, he undertook the first of several voy‑ ages to America, joining a Spanish fleet to the Caribbean. His record of this voyage, including illustrations and first-hand de‑ scriptions of the Spanish empire and their rule over American Indians, won him the attention and support of Henry IV, king of France.
Image \(\PageIndex{1}\): Samuel de Champlain
As Royal Geographer, he joined Francois Pont-Grave’s expedition charged with establishing a French colony in America. He sailed up the Saint Lawrence River and proposed a settlement at what is now the lower town of Quebec City. His written reports on America, first with Des Sauvages (of the Indians) (1604) followed by his Les Voyages (1613) did much to encourage French interest in America.
He defended the small colony through alliances with the Montagnais, the Algonquians, and the Hurons, joining them in a fierce battle against the Mohawk in what is now central New York. He died on Christmas Day in 1635 and was buried at Notre Dame de la Recouvance, a Catholic church he founded in what is now Quebec City. He is still known as the father of New France.


6.2.4: Metal Carbonyls
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Learning Objectives
In this lecture you will learn the following
- The historical background of metal carbonyl complexes.
- The CO ligand and its binding ability to metal.
- Synergism between the ligand to metal forward σ–donation and the metal to ligand backward π–donation observed in a metal-CO interaction.
- The synthesis, characterization and their reactivity of the metal carbonyl compounds.
Metal carbonyls are important class of organometallic compounds that have been studied for a long time. Way back in 1884, Ludwig Mond, upon observing that the nickel valves were being eating away by CO gas in a nickel refining industry, heated nickel powder in a stream of CO gas to synthesize the first known metal carbonyl compound in the form Ni(CO) 4 . The famous Mond refining process was thus born, grounded on the premise that the volatile Ni(CO) 4 compound can be decomposed to pure metal at elevated temperature. Mond subsequently founded the Mond Nickel Company Limited for purifying nickel from its ore using this method.
The carbonyl ligand (CO) distinguishes itself from other ligands in many respects. For example, unlike the alkyl ligands, the carbonyl (CO) ligand is unsaturated thus allowing not only the ligand to σ−donate but also to accept electrons in its π* orbital from d π metal orbitals and thereby making the CO ligand π−acidic. The other difference lies in the fact that CO is a soft ligand compared to the other common σ−and π−basic ligands like H 2 O or the alkoxides (RO−), which are considered as hard ligands.
Being π−acidic in nature, CO is a strong field ligand that achieves greater d −orbital splitting through the metal to ligand π−back donation. A metal−CO bonding interaction thus comprises of a CO to metal σ−donation and a metal to CO π−back donation (Figure \(\PageIndex{1}\)). Interestingly enough, both the spectroscopic measurements and the theoretical studies suggest that the extent of the metal to CO π−back donation is almost equal to or even greater than the extent of the CO to metal σ−donation in metal carbonyl complexes. This observation is in agreement with the fact that low valent−transition metal centers tend to form metal carbonyl complexes.
In the metal carbonyl complexes, the direct bearing of the π−back donation is observed on the M−C bond distance that becomes shorter as compared to that of a normal M−C single bond distance. For example, the CpMo(CO) 3 CH 3 complex, exhibits two kind of M−C bond distances that comprise of a longer Mo−CH 3 distance (2.38 Å) and a much shorter Mo−CO distance (1.99 Å) arising out of a metal to ligand π−back donation. It becomes thus apparent that the metal−CO interaction can be easily characterized using X−ray crystallography. The infrared spectroscopy can also be equally successfully employed in studying the metal−CO interaction. Since the metal to CO π−back bonding involves a π−donation from the metal d π orbital to a π* orbital of a C−O bond, significant shift of the ν(CO) stretching frequency towards the lower energy is observed in metal carbonyl complexes with respect to that of free CO (2143 cm −1 ).
Preparation of metal carbonyl complexes
The common methods of the preparation of the metal carbonyl compounds are,
i. Directly using CO
\[\ce{Fe ->[CO, \: 200atm, \: 200°C] Fe(CO)5} \nonumber \]
The main requirement of this method is that the metal center must be in a reduced low oxidation state in order to facilitate CO binding to the metal center through metal to ligand π−back donation.
ii. Using CO and a reducing agent
\[\ce{NiSO4 + CO + S2O4^{2-} -> Ni(CO)4} \nonumber \]
This method is commonly called reductive carbonylation and is mainly used for the compounds having higher oxidation state metal centers. The reducing agent first reduces the metal center to a lower oxidation state prior to the binding of CO to form the metal carbonyl compounds.
iii. From carbonyl compounds
This method involves abstraction of CO from organic compounds like the alcohols, aldehydes and CO
2
.
Reactivities of metal carbonyls
i. Nucleophilic attack on carbon
The reaction usually gives rise to carbene moiety.
ii. Electrophilic attack at oxygen
\[\ce{Cl(PR3)4Re-CO + AlMe3 -> Cl(PR3)4Re-CO -> AlMe3} \nonumber \]
iii. Migratory insertion reaction
\[\ce{MeMn(CO)5 +PMe3 -> (MeCO)Mn(CO)4(PMe3)} \nonumber \]
The metal carbonyl displays two kinds of bindings in the form of the terminal and the bridging modes. The infrared spectroscopy can easily distinguish between these two binding modes of the metal carbonyl moiety as the terminal ones show ν(CO) stretching band at ca . 2100-2000 cm −1 while the bridging ones appear in the range 1720−1850 cm −1 . The carbonyl moiety can bridge between more than two metal centers (Figure \(\PageIndex{2}\)).
Problems
1. How many lone pairs are there in the CO molecule?
Ans: Three (one from carbon and two from oxygen).
2. Despite O being more electronegative than C, the dipole moment of CO is almost zero. Explain.
Ans: Because of the electron donation from oxygen to carbon.
3. What type of metal centers form metal carbonyl complexes?
Ans: Low−valent metal centers.
4. What are the two main modes of binding exhibited by CO ligand?
Ans: Terminal and bridging modes of binding.
Self Assessment test
1. Predict the product of the reaction?
\[\ce{Ni + CO_{Excess} ->} \nonumber \]
Ans: Three (one from carbon and two from oxygen).
2. Upon binding to a metal center the C−O stretching frequency increases/decreases with regard to that of the free CO?
Ans: Decreases.
3. Explain why do low−valent metal centers stabilize CO binding in metal carbonyl complexes?
Ans: Because metal to ligand π−back donation.
4. Give an example of a good σ−donor and π−donor ligand?
Ans: Alkoxides (RO - ).
Summary
CO is a hallmark ligand of organometallic chemistry. The metal carbonyl complexes have been studied for a long time. The CO ligands bind tightly to metal center using a synergistic mechanism that involves σ−donation of the ligand lone pair to metal and followed by the π−back donation from a filled metal d orbital to a vacant σ* orbital of C−O bond of the CO ligand. The metal carbonyl complexes are prepared by several methods. The metal carbonyl complexes are usually stabilized by metal centers in low oxidation states.


8.1: Introduction
Module 8
Metamorphism and Metamorphic Rock
Introduction
In any introductory textbook on physical geology, the reader will find the discussion on metamorphic rocks located after the chapters on igneous and sedimentary rocks, and for very good reason. Metamorphic rocks form by the physical and sometimes chemical alteration of a pre-existing rock, whether it is igneous or sedimentary. In some cases, even metamorphic rocks can be altered into a completely different metamorphic rock. With igneous rocks forming from the melt produced by any rock type and a sedimentary rock forming from the weathered product of any rock type, the alteration of any rock to produce a metamorphic one completes the components of what is known as the rock cycle.
Basically, the rocks we encounter today that we classify as either igneous, metamorphic, or sedimentary, could have belonged to a different rock classification in the past, because rocks are recycled throughout geologic time. This cycle is driven by the motion of the tectonic plates. It is easy to see that increasing the temperature of a rock can produce magma, and that rocks on the surface of the Earth can break up into sediment that can ultimately lithify into a sedimentary rock. But how can we alter a solid rock into a new rock, without melting it or making it become sediment?
All rocks are formed at certain temperatures and pressures either on Earth’s surface or, more commonly, beneath the surface. These rocks are the most stable at the conditions under which they form. Therefore, changing the temperature and/or pressure conditions may lead to a different rock, one that changed in order to be stable under new external conditions. This new rock that forms in response to changes in its physical and chemical environment is called a metamorphic rock; the word metamorphism means to change form, and for rocks this means a recrystallization of minerals (crystals) under subsolidus (temperatures too low for melt production) conditions. A metamorphic change can also occur if the rock’s composition is altered by hot, chemically reactive fluids, causing a change in the mineral content of the rock. To distinguish between the pre-existing rock and the new metamorphic one, the term protolith, or parent rock, is used to describe the pre-existing rock. Therefore, all metamorphic rocks have at least one protolith that has altered during metamorphism. In this module you will learn that all metamorphic rocks are identified by the mineral content and texture of the rock; for metamorphic rocks, texture refers to the orientation of the minerals in the rock. In addition, crystal size also conveys important information regarding the temperature conditions during metamorphism.
To summarize, metamorphism is the process by which a pre-existing rock (the protolith) is altered by a change in temperature, pressure, or by contact with chemically reactive fluids, or by any combination of these three parameters. The alteration process is a recrystallization event, where the initial rock’s minerals (crystals) have changed size, shape, and/or composition in response to these new external conditions. The end result is a new (metamorphic) rock that has an altered appearance, sometimes strikingly different from what it used to look like before metamorphism occurred. The metamorphic rock you end up with is strongly dependent on what rock you started with before the metamorphic event. Of secondary importance is the agent of metamorphic change: was recrystallization a result of increased temperature, pressure, or both? Or were chemically reactive fluids involved?
One must also consider how high the temperatures and pressures were, because metamorphism can occur in a range of temperature and pressure conditions. However, as mentioned in the preceding paragraph, metamorphism occurs under subsolidus conditions, meaning that elevated temperatures that promote the recrystallization of a rock are not high enough to cause melting.
Select an image to view larger
Module Objectives
At the completion of this module you will be able to:
- Summarize the factors that influence the nature of metamorphic rocks and the mechanisms for the formation of foliation, if present.
- Classify metamorphic rocks on the basis of their texture and mineral content, and explain the origins of these differences.
- Describe the various settings in which metamorphic rocks are formed and explain the links between plate tectonics and metamorphism.
- Summarize the important processes of regional metamorphism, and explain how rocks that were metamorphosed at depths of 10 km or 20 km can now be found on Earth’s surface.
- Summarize the important processes of contact metamorphism and metasomatism, and explain the key role of hydrothermal fluids.
Activities Overview
See the Schedule of Work for dates of availability and due dates.
Be sure to read through the directions for all of this module’s activities before getting started so that you can plan your time accordingly. You are expected to work on this course throughout the week.
Read
Physical Geology by Steven Earle
- Chapter 7 (Metamorphism and Metamorphic Rock)
Module 8 Assignment: Metamorphic Rock Lab
10 points
After you complete the reading, you can start working on Module 8 Assignment – Metamorphic Rock Lab
Module 8 Quiz
10 points
Module 8 Quiz has 10 multiple-choice questions and is based on the content of the Module 8 readings and Assignment 8.
The quiz is worth a total of 10 points (1 points per question). You will have only 10 minutes to complete the quiz, and you may take this quiz only once. Note : that is not enough time to look up the answers!
Make sure that you fully understand all of the concepts presented and study for this quiz as though it were going to be proctored in a classroom, or you will likely find yourself running out of time.
Keep track of the time, and be sure to look over your full quiz results after you have submitted it for a grade.
Your Questions and Concerns…
Please contact me if you have any questions or concerns.
General course questions : If your question is of a general nature such that other students would benefit from the answer, then go to the discussions area and post it as a question thread in the “General course questions” discussion area.
Personal questions : If your question is personal, (e.g. regarding my comments to you specifically), then send me an email from within this course.


12.2: Contours of the Industry
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- Heather Berg & Constance Penley
- University of California Press
Though increasingly diffuse, the adult film industry occupies a central role in the spatial and political economy of California’s San Fernando Valley. We focus our inquiry there in the interests of space and precision, while also attending to the growing production centers of Las Vegas, San Francisco, south Florida, and globally, Brazil and Eastern Europe. A small roster of production and distribution companies, including Manwin, Bang Brothers, Brazzers, West Coast Productions, Evil Angel, Wicked Pictures, Larry Flynt Productions, Playboy Enterprises, and Vivid Entertainment, dominates the adult film industry landscape. But as production costs rise and potential profits from large-scale productions decrease, 4 small, boutique production companies producing niche content increasingly populate the adult film industry. In using the term industry , we do not suggest a monolithic, static, or internally consistent body. Instead, we mean to indicate the dynamic networks of workers, management, and institutions that take part in the production process of adult film, all of which are affected by regulatory policies such as Measure B, the 2012 Los Angeles County mandatory condom law that saw more than a 90 percent drop in adult film production permits issued.
Studio executives, investors, producers, talent agents, directors, crew, performers, postproduction editors, and distribution and marketing staff are key players in adult film production. Common institutions connect these actors: trade publications distribute industry news and host annual trade and award shows; the industry’s trade organization, the Free Speech Coalition, lobbies on its behalf and, since the 2010 collapse of what had been an industry-run health clinic, sets the terms for recommended sexually transmitted infection (STI) testing panels and exposure protocols; the Adult Performer Advocacy Committee (APAC), since the fall of 2013, provides worker education such as the Porn 101 video and brings performers together to advocate on their own behalf in discussions of testing protocols and other informal policies; and private but industry-specific testing clinics clear performers for work. Other institutions and actors, while not of the porn industry, are intimately connected to it: multinational software development firms design web platforms and process credit card payments, real estate agents coordinate filming locations, beauty service providers specialize in readying performers for work, publicity firms cater to performers and adult businesses, and nonprofit organizations such as the Aids Healthcare Foundation build political identities and funding bases through their relationships with (or stark opposition to) the industry. In describing the contours of the “industry,” we think it is important to include organizations and institutions that could not exist without the adult industry, such as for-profit “porn addiction” therapies, religious antiporn initiatives like the XXX-CHURCH, which sends its preachers on the college circuit to debate with porn stars (“Jesus loves porn stars!”), and the antiporn feminists who spend extraordinary amounts of time and energy fighting not only the adult industry but those who think it merits study rather than blanket condemnation (Stop Porn Culture).
We also understand the “industry” to encompass the satellite industries—including erotic dance, webcam, escort, and novelty—that enjoy a symbiotic relationship with the adult film industry. This relationship has three dimensions: first, income streams from satellite industries economically sustain adult film performers, securing a reserve army of performer labor for whom the film industry is not financially responsible. Were such income streams not available, it would be difficult if not impossible for performers to maintain themselves amid the vicissitudes of demand, filming schedules, industry, and other factors that mean a performer might work twenty days one month and two the next. 5 Second, many performers describe the increased earnings they can draw from satellite industries by marketing themselves as “porn stars” as a primary reason for taking on porn performance. 6 Dominic Ace, an adult industry publicist and photographer who has worked as a roadie for performers on feature dancing tours, explained it this way: “You’ve got web sites, you’ve got Skype shows, you’ve got privates [escorting], you’ve got fan clubs, you’ve got custom videos, appearances, feature dancing, Verified Call [a service that connects fans to performers via cell phone], a ton of different revenue streams. . . . You don’t make money doing scenes, a scene is a marketing tool [emphasis added].” 7 Talent agents for film frequently recruit in erotic dance clubs and on webcam sites, and adult actresses report having begun careers in these fields, later moving into the film industry. Finally, production companies and agents who sign performers to exclusive contracts may be, depending on the specific terms of the contract, entitled to a percentage of workers’ earnings in satellite industries.
Porn workers push the boundaries of the industry to meet their financial needs, as well as satisfy desires for autonomy, flexibility, and work-life balance. Porn performer and single parent Raylene explained that her average take from three to five hours of webcamming work was comparable to her film performance rate, but webcamming allowed her to have greater control over her schedule and working environment: “I was able to work alone, in my house, during school hours, and then, you know, have the rest of the evening with my child and make a better living at home than when I was in front of the camera.” 8 Those performers who prefer satellite industries to adult filmmaking describe taking just enough film gigs to maintain their “brands.” In line with Dominic Ace’s description of scenes as “marketing tool[s],” performer Venus Lux noted, “When you’re in porn, especially transsexual porn, it’s not a money making thing. It’s for the fame, that’s it. The chain reaction of the fame means you can eventually get money.” 9 Management too is keenly aware of the industry’s reliance on satellite industries. Christian Mann, a longtime board member of the industry’s trade organization and general manager of distribution giant Evil Angel, compared the porn industry’s increasing reliance on alternative profit streams to similar trends in the mainstream music industry. “The reality is,” he wrote, “albums don’t make money anymore. Record stores are gone, right? So the saving grace for the music industry has been concert tickets.” 10


5.8: Kinematic analysis with the path coordinate s
In some cases the velocity \(v_{s, i}(s)\), acceleration \(a_{s, i}(s)\) or time \(t_{s}(s)\) as a function of path coordinate \(s\) is known, but the explicit time dependence is unknown. In those cases it can be more convenient to choose \(s\) as an independent differentiation or integration variable than \(t\).
Note well, the function \(v_{s, i}(s)\) is mathematically different from the function \(v_{s, i}(t)\), and that also holds for and \(a_{s, i}(s)\) and \(a_{s, i}(t)\). These functions are connected by the relations \(v_{s, i}(s(t))=v_{s, i}(t)\) and \(a_{s, i}(s(t))=a_{s, i}(t)\) that should hold at any time. The difference by these functions will be designated by clearly indicating between brackets the variable on which they depend \(\left(v_{s, i}(t)\right.\) or \(\left.v_{s, i}(s)\right)\).
5.8.1 Path differentiation
If we take the time derivative of the function \(v_{s, i}(s)\) we obtain using the chain rule:
\[a_{s, i}(s)=\frac{\mathrm{d} v_{s, i}(s)}{\mathrm{d} t}=\frac{\mathrm{d} v_{s, i}(s)}{\mathrm{d} s} \frac{\mathrm{d} s_{i}}{\mathrm{~d} t}=\frac{\mathrm{d} v_{s, i}(s)}{\mathrm{d} s} v_{s, i}(s) \tag{5.43} \label{5.43}\]
This equation can be used to obtain the acceleration function \(a_{s, i}(s)\) from \(v_{s, i}(s)\).
5.8.2 Path integration
When the acceleration \(a_{s, i}(s)\) is known as a function of the path coordinate \(s\) instead of as a function of time, the following differential equation needs to be solved to obtain the velocity \(v_{s, i}(s)\) :
\[a_{s, i}(s)=\frac{\mathrm{d} v_{s, i}}{\mathrm{~d} t}=\ddot{s}_{i} \tag{5.44} \label{5.44}\]
After multiplying the equation on both sides by \(\mathrm{d} s\), and using that \(\frac{\mathrm{d} v_{s, i}}{\mathrm{~d} t} \mathrm{~d} s=\) \(\mathrm{d} v \frac{\mathrm{d} s_{i}}{\mathrm{~d} t}=v_{s, i} \mathrm{~d} v_{s, i}\) the differential equation can be solved by integration:
\[\int_{s_{1}}^{s_{2}} a_{s, i} \mathrm{~d} s=\int_{v_{1}}^{v_{2}} v_{s, i} \mathrm{~d} v_{s, i}=\left[\frac{1}{2} v_{s, i}^{2}\right]_{v_{1}}^{v_{2}}=\frac{1}{2}\left(v_{2}^{2}-v_{1}^{2}\right) \tag{5.45} \label{5.45}\]
Where \(v_{1}\) and \(v_{2}\) are the velocity of the point mass at the positions \(s_{1}\) and \(s_{2}\), \(v_{1}=v_{s, i}\left(s_{1}\right)\) and \(v_{2}=v_{s, i}\left(s_{2}\right)\). This equation can be rewritten in a form that allows finding \(v_{s, i}\) from \(a_{s, i}\) :
\[v_{s, i}^{2}\left(s_{2}\right)=v_{s, i}^{2}\left(s_{1}\right)+2 \int_{s_{1}}^{s_{2}} a_{s, i}(s) \mathrm{d} s \tag{5.46} \label{5.46}\]
We note that the relation \(a_{s} \mathrm{~d} s=v_{s} \mathrm{~d} v_{s}\) that appears under the integrals in Equation 5.45 is often useful to simplify expressions for differentiation and integration with the path coordinate \(s\).
5.8.3 Velocity dependent acceleration
A final case that can become of relevance, is when acceleration \(a_{s, i}(v)\) depends on velocity. To obtain the velocity as a function of time \(v_{s, i}(t)\) one needs to solve this differential equation:
\[\frac{\mathrm{d} v_{s, i}}{\mathrm{~d} t}=a_{s, i}(v) \tag{5.47} \label{5.47}\]
The strategy for solving this kind of ODE is to rearrange all terms such that terms depending on \(t\) are on one side of the equal side and terms depending on \(v\) are on the other side. Here that is done by multiplying both sides by \(\mathrm{d} t\) and dividing them by \(a_{s, i}\) and then integrating:
\[\int_{v_{1}}^{v_{s}} \frac{\mathrm{d} v_{s, i}}{a_{s, i}(v)}=\int_{t_{1}}^{t_{s}} \mathrm{~d} t=t_{s}-t_{1} \tag{5.48} \label{5.48}\]
By evaluating this integral and using the information on the initial condition at \(t_{1}\), one obtains a function \(t_{s}\left(v_{s}\right)\), which can be inverted to give the velocity as a function of time \(v_{s}\left(t_{s}\right)\). Alternatively, if one is looking for the function \(v_{s}(s)\) it is possible to multiply both sides of the differential equation (5.47) by \(\mathrm{d} s\), divide by \(a_{s, i}\) and integrate to obtain:
\[\int_{v_{1}}^{v_{s}} \frac{\mathrm{d} v_{s, i}}{a_{s, i}(v)} v_{s, i}=\int_{s_{1}}^{s} \mathrm{~d} s^{\prime}=s-s_{1} \tag{5.49} \label{5.49}\]
Using the initial condition this gives \(s\left(v_{s}\right)\) which can be inverted to obtain \(v_{s}(s)\).
5.8.4 Overview integration and differentiation in kinematics
After having discussed several ways to differentiate and integrate the kinematics when motion is along a one-dimensional path curve, we provide here an overview table with all equations for reference. The equations for integrating and differentiating between the different kinematic variables \(a, v, s\) and \(t\) as a function of each other are summarised in Table 5.1 below. Please note that the cases with \(t\) as dependent variable are usually the most important. Moreover, realise that it is better to learn how to properly derive these equations yourself by integrating and differentiation than to memorise equations.
5.8.5 Numerical differentiation and integration
Often, expressions are too complicated to differentiate or integrate using analytical equations. However in those cases the integration can usually still be performed numerically.
- Advantages of numerical methods:
- Can solve almost all problems
- No need to perform (difficult) analytical integration or differentiation
- Disadvantages of numerical methods:
| \(a_{s}()\) | \(v_{s}()\) | \(s()\) | \(t_{s}()\) | |
|---|---|---|---|---|
| \(t\) | \(a_{s}(t)=\frac{d v_{s}(t)}{d t}\) | \(v_{s}(t)=\frac{\mathrm{ds}(t)}{\mathrm{d} t}\) | \(s(t)=t_{s}^{t^{-}}\) | |
| \(t\) | \(v_{s}(t)=v_{s}\left(t_{1}\right)+\int_{t_{1}}^{t} a_{s}\left(t^{\prime}\right) \mathrm{d} t^{\prime}\) | \(s(t)=s\left(t_{1}\right)+\int_{t_{1}}^{t} v_{s}\left(t^{\prime}\right) \mathrm{d} t^{\prime}\) | ||
| s | \(a_{s}(s)=v_{s}(s) \frac{\mathrm{d} v_{s}(s)}{\mathrm{d} s}\) | \(v_{s}(s)=\left(\frac{\mathrm{d} t_{s}(s)}{\mathrm{d} s}\right)^{-}\) | \(t_{s}(s)=s^{\langle-1\rangle}(t)\) | |
| \(s\) | \(v_{s}^{2}(s)=v_{s}^{2}\left(s_{1}\right)+2 \int_{s_{1}}^{s} a_{s}\left(s^{\prime}\right) \mathrm{d} s^{\prime}\) | \(t_{s}(s)=t_{s}\left(s_{1}\right)+\int_{s_{1}}^{s} \frac{d_{s} s^{\prime}}{\left.v_{s}\right)}\) | ||
| \(v\) | \(a_{s}(v)=\left(\frac{d t_{s}(v)}{d v}\right)^{-}\) | \(s(v)=v_{s}^{\langle-1\rangle}(s)\) | \(t_{s}(v)=v_{s}^{\langle-1\rangle}(t)\) | |
| \(v\) | \(a_{s}(v)=v\left(\frac{\mathrm{d} s(v)}{\mathrm{d} v}\right)\) | \(\left.s(v)=s\left(v_{1}\right)+\int_{v_{1}}^{v} \frac{v_{s}^{\prime}\left(v_{v}\right.}{v^{\prime}}\right)\) | \(\left.t_{s}(v)=t_{s}\left(v_{1}\right)+\int_{v_{1}}^{v} \frac{d v^{\prime}}{\left.a_{s}\right)^{\prime}}\right)\) |
Table 5.1: Equations to relate different kinematic quantities along the path curve \(a, v, s\) and \(t\) as a function of each other. The top row indicates the function and dependent variable, while the left column indicates the independent variable. For example, the function \(s(t)\) can be obtained in 2 ways: either by time integrating the function \(v_{s}(t)\) or by taking the inverse function of the function \(t_{s}(s)\). Note that \(t_{s}^{\langle-1\rangle}(s)\) in this table indicates the inverse function of \(t_{s}(s)\), not \(1 / t_{s}(s)\).
- Less accurate and fast than computing an analytic solution
- Programming required
- Gives less insight because only one specific solution is found, not the dependence on variables
To numerically determine the time derivative of a known function \(s_{A}(t)\), you determine the position \(s_{A}\) at two closely spaced points in time \(s_{A}(t)\) and \(s_{A}(t+\Delta t)\), with a small time difference \(\Delta t\). The simplest numerical differentiation in formula form is then performed using this equation:
\[v_{s, A}(t) \approx \frac{s_{A}(t+\Delta t)-s_{A}(t)}{\Delta t} \tag{5.50} \label{5.50}\]
This equation can be applied for all values of \(t\) to obtain \(v_{s, A}(t)\). According to the definition of the derivative, this expression becomes exactly correct in the limit \(\Delta t \rightarrow 0\) which allows improving the numerical accuracy as much as needed by reducing the time step \(\Delta t\).
If instead the velocity \(v_{s, A}(t)\) is known, the position \(s_{A}\) can be determined by numerical time integration by just rewriting the previous equation to:
\[s_{A}(t+\Delta t)=s_{A}(t)+v_{s, A}(t) \Delta t \tag{5.51} \label{5.51}\]
This equation can be applied iteratively to obtain \(s_{A}(t+\Delta t)\) at a next time from its value \(s_{A}(t)\) at a previous time. For example the next step is:
\[s_{A}(t+2 \Delta t)=s_{A}(t+\Delta t)+v_{s, A}(t+\Delta t) \Delta t \tag{5.52} \label{5.52}\]
This integration procedure, which is called the Euler forward method, can be iterated to get the complete numerical integral for \(s_{A}\) for all times. Reducing
the time step \(\Delta t\) helps to increase the accuracy. The method can also be applied to integrate acceleration and velocity vectors, by performing scalar integration along each of the axes in a Cartesian system like in eq. (5.57). There are multiple methods for numerically solving integrals and obtaining derivatives. An important integration method is Euler’s forward method, which is the simplest but by far not the most efficient and accurate method. To be sure of a result, it can be a good strategy to solve a problem both analytically and numerically. Then the numerical solution can function as a plausibility check for the analytical solution or vice versa.


6.5: Angular Momentum and Its Conservation
Learning Objectives
- Understand the analogy between angular momentum and linear momentum.
- Observe the relationship between torque and angular momentum.
- Apply the law of conservation of angular momentu
Why does Earth keep on spinning? What started it spinning to begin with? And how does an ice skater manage to spin faster and faster simply by pulling her arms in? Why does she not have to exert a torque to spin faster? Questions like these have answers based in angular momentum, the rotational analog to linear momentum.
By now the pattern is clear—every rotational phenomenon has a direct translational analog. It seems quite reasonable, then, to define angular momentum \(L\) as
\[L=I \omega. \nonumber \]
This equation is an analog to the definition of linear momentum as \(p=m v\). Units for linear momentum are \(\mathrm{kg} \cdot \mathrm{m} / \mathrm{s}\) while units for angular momentum are \(\mathrm{kg} \cdot \mathrm{m}^{2} / \mathrm{s}\). As we would expect, an object that has a large moment of inertia \(I\), such as Earth, has a very large angular momentum. An object that has a large angular velocity \(\omega\), such as a centrifuge, also has a rather large angular momentum.
Example \(\PageIndex{1}\): Calculating Angular Momentum of the Earth
Strategy
No information is given in the statement of the problem; so we must look up pertinent data before we can calculate \(L=I \omega\). First, according to Figure 10.3.3 from [link] , the formula for the moment of inertia of a sphere is
\[I=\frac{2 M R^{2}}{5} \nonumber\]
so that
\[L=I \omega=\frac{2 M R^{2} \omega}{5}. \nonumber\]
Earth’s mass \(M\) is \(5.979 \times 10^{24} \mathrm{~kg}\) and its radius \(R\) is \(6.376 \times 10^{6} \mathrm{~m}\). The Earth’s angular velocity \(\omega\) is, of course, exactly one revolution per day, but we must covert \(\omega\) to radians per second to do the calculation in SI units.
Solution
Substituting known information into the expression for \(L\) and converting \(\omega\) to radians per second gives
\[\begin{aligned}
L &=0.4\left(5.979 \times 10^{24} \mathrm{~kg}\right)\left(6.376 \times 10^{6} \mathrm{~m}\right)^{2}\left(\frac{1 \; \mathrm{rev}}{\mathrm{d}}\right) \\
&=9.72 \times 10^{37} \mathrm{~kg} \cdot \mathrm{m}^{2} \cdot \mathrm{rev} / \mathrm{d}.
\end{aligned} \nonumber\]
Substituting \(2 \pi\) rad for \(1\) rev and \(8.64 \times 10^{4}\) for 1 day gives
\[\begin{aligned}
L &=\left(9.72 \times 10^{37} \mathrm{~kg} \cdot \mathrm{m}^{2}\right)\left(\frac{2 \pi \; \mathrm{rad} / \mathrm{rev}}{8.64 \times 10^{4} \mathrm{~s} / \mathrm{d}}\right)(1 \; \mathrm{rev} / \mathrm{d}) \\
&=7.07 \times 10^{33} \mathrm{~kg} \cdot \mathrm{m}^{2} / \mathrm{s}.
\end{aligned} \nonumber\]
Discussion
This number is large, demonstrating that Earth, as expected, has a tremendous angular momentum. The answer is approximate, because we have assumed a constant density for Earth in order to estimate its moment of inertia.
When you push a merry-go-round, spin a bike wheel, or open a door, you exert a torque. If the torque you exert is greater than opposing torques, then the rotation accelerates, and angular momentum increases. The greater the net torque, the more rapid the increase in \(L\). The relationship between torque and angular momentum is
\[\text { net } \tau=\frac{\Delta L}{\Delta t}. \nonumber \]
This expression is exactly analogous to the relationship between force and linear momentum, \(F=\Delta p / \Delta t\). The equation \(\text { net } \tau=\frac{\Delta L}{\Delta t}\) is very fundamental and broadly applicable. It is, in fact, the rotational form of Newton’s second law.
Example \(\PageIndex{2}\): Calculating the Torque Putting Angular Momentum Into a Lazy Susan
Figure \(\PageIndex{1}\) shows a Lazy Susan food tray being rotated by a person in quest of sustenance. Suppose the person exerts a 2.50 N force perpendicular to the lazy Susan’s 0.260-m radius for 0.150 s. (a) What is the final angular momentum of the lazy Susan if it starts from rest, assuming friction is negligible? (b) What is the final angular velocity of the lazy Susan, given that its mass is 4.00 kg and assuming its moment of inertia is that of a disk?
Strategy
We can find the angular momentum by solving \(\text { net } \tau=\frac{\Delta L}{\Delta t}\) for \(\Delta L\), and using the given information to calculate the torque. The final angular momentum equals the change in angular momentum, because the lazy Susan starts from rest. That is, \(\Delta L=L\). To find the final velocity, we must calculate \(\omega\) from the definition of \(L\) in \(L=I \omega\).
Solution for (a)
Solving \(\text { net } \tau=\frac{\Delta L}{\Delta t}\) for \(\Delta L\) gives
\[\Delta L=(\operatorname{net} \tau) \Delta \mathrm{t}. \nonumber\]
Because the force is perpendicular to \(R\), we see that \(\text { net } \tau=r F\), so that
\[\begin{aligned}
L &=\mathrm{rF} \Delta t=(0.260 \mathrm{~m})(2.50 \mathrm{~N})(0.150 \mathrm{~s}) \\
&=9.75 \times 10^{-2} \mathrm{~kg} \cdot \mathrm{m}^{2} / \mathrm{s}.
\end{aligned} \nonumber\]
Solution for (b)
The final angular velocity can be calculated from the definition of angular momentum,
\[L=I \omega. \nonumber\]
Solving for \(\omega\) and substituting the formula for the moment of inertia of a disk into the resulting equation gives
\[\omega=\frac{L}{I}=\frac{L}{\frac{1}{2} M R^{2}}. \nonumber\]
And substituting known values into the preceding equation yields
\[\omega=\frac{9.75 \times 10^{-2} \mathrm{~kg} \cdot \mathrm{m}^{2} / \mathrm{s}}{(0.500)(4.00 \mathrm{~kg})(0.260 \mathrm{~m})}=0.721 \mathrm{rad} / \mathrm{s}. \nonumber\]
Discussion
Note that the imparted angular momentum does not depend on any property of the object but only on torque and time. The final angular velocity is equivalent to one revolution in 8.71 s (determination of the time period is left as an exercise for the reader), which is about right for a lazy Susan.
MAKING CONNECTIONS: CONSERVATION LAWS
Angular momentum, like energy and linear momentum, is conserved. This universally applicable law is another sign of underlying unity in physical laws. Angular momentum is conserved when net external torque is zero, just as linear momentum is conserved when the net external force is zero.
Conservation of Angular Momentum
We can now understand why Earth keeps on spinning. As we saw in the previous example, \(\Delta L=(\operatorname{net} \tau) \Delta t\). This equation means that, to change angular momentum, a torque must act over some period of time. Because Earth has a large angular momentum, a large torque acting over a long time is needed to change its rate of spin. So what external torques are there? Tidal friction exerts torque that is slowing Earth’s rotation, but tens of millions of years must pass before the change is very significant. Recent research indicates the length of the day was 18 h some 900 million years ago. Only the tides exert significant retarding torques on Earth, and so it will continue to spin, although ever more slowly, for many billions of years.
What we have here is, in fact, another conservation law. If the net torque is zero , then angular momentum is constant or conserved . We can see this rigorously by considering \(\text { net } \tau=\frac{\Delta L}{\Delta t}\) for the situation in which the net torque is zero. In that case,
\[\operatorname{net} \tau=0 \nonumber \]
implying that
\[\frac{\Delta L}{\Delta t}=0. \nonumber \]
If the change in angular momentum \(\Delta L\) is zero, then the angular momentum is constant; thus,
\[L=\text { constant }(\text { net } \tau=0) \nonumber \]
or
\[L=L^{\prime}(\operatorname{net} \tau=0) . \nonumber \]
These expressions are the law of conservation of angular momentum . Conservation laws are as scarce as they are important.
An example of conservation of angular momentum is seen in Figure \(\PageIndex{2}\), in which an ice skater is executing a spin. The net torque on her is very close to zero, because there is relatively little friction between her skates and the ice and because the friction is exerted very close to the pivot point. (Both \(F\) and \(R\) are small, and so \(\tau\) is negligibly small.) Consequently, she can spin for quite some time. She can do something else, too. She can increase her rate of spin by pulling her arms and legs in. Why does pulling her arms and legs in increase her rate of spin? The answer is that her angular momentum is constant, so that
\[L=L^{\prime}. \nonumber \]
Expressing this equation in terms of the moment of inertia,
\[I \omega=I^{\prime} \omega^{\prime}, \nonumber \]
where the primed quantities refer to conditions after she has pulled in her arms and reduced her moment of inertia. Because \(I^{\prime}\) is smaller, the angular velocity \(\omega^{\prime}\) must increase to keep the angular momentum constant. The change can be dramatic, as the following example shows.
Example \(\PageIndex{3}\): Calculating the Angular Momentum of a Spinning Skater
Suppose an ice skater, such as the one in Figure \(\PageIndex{2}\), is spinning at 0.800 rev/ s with her arms extended. She has a moment of inertia of \(2.34 \mathrm{~kg} \cdot \mathrm{m}^{2}\) with her arms extended and of \(0.363 \mathrm{~kg} \cdot \mathrm{m}^{2}\) with her arms close to her body. (These moments of inertia are based on reasonable assumptions about a 60.0-kg skater.) (a) What is her angular velocity in revolutions per second after she pulls in her arms? (b) What is her rotational kinetic energy before and after she does this?
Strategy
In the first part of the problem, we are looking for the skater’s angular velocity \(\omega^{\prime}\) after she has pulled in her arms. To find this quantity, we use the conservation of angular momentum and note that the moments of inertia and initial angular velocity are given. To find the initial and final kinetic energies, we use the definition of rotational kinetic energy given by
\[\mathrm{KE}_{\mathrm{rot}}=\frac{1}{2} I \omega^{2}. \nonumber\]
Solution for (a)
Because torque is negligible (as discussed above), the conservation of angular momentum given in \(I \omega=I^{\prime} \omega^{\prime}\) is applicable. Thus,
\[L=L^{\prime} \nonumber\]
or
\[I \omega=I^{\prime} \omega^{\prime} \nonumber\]
Solving for \(\omega^{\prime}\) and substituting known values into the resulting equation gives
\[\begin{aligned}
\omega^{\prime} &=\frac{I}{I^{\prime}} \omega=\left(\frac{2.34 \mathrm{~kg} \cdot \mathrm{m}^{2}}{0.363 \mathrm{~kg} \cdot \mathrm{m}^{2}}\right)(0.800 \mathrm{rev} / \mathrm{s}) \\
&=5.16 \mathrm{rev} / \mathrm{s}.
\end{aligned} \nonumber\]
Solution for (b)
Rotational kinetic energy is given by
\[\mathrm{KE}_{\mathrm{rot}}=\frac{1}{2} I \omega^{2}. \nonumber\]
The initial value is found by substituting known values into the equation and converting the angular velocity to rad/s:
\[\begin{aligned}
\mathrm{KE}_{\mathrm{rot}} &=(0.5)\left(2.34 \mathrm{~kg} \cdot \mathrm{m}^{2}\right)((0.800 \mathrm{rev} / \mathrm{s})(2 \pi \mathrm{rad} / \mathrm{rev}))^{2} \\
&=29.6 \mathrm{~J}.
\end{aligned} \nonumber\]
The final rotational kinetic energy is
\[\mathrm{KE}_{\mathrm{rot}}^{\prime}=\frac{1}{2} I^{\prime} \omega^{\prime 2}. \nonumber\]
Substituting known values into this equation gives
\[\begin{aligned}
K E_{\text {rot }}^{\prime} &=(0.5)\left(0.363 \mathrm{~kg} \cdot \mathrm{m}^{2}\right)[(5.16 \mathrm{rev} / \mathrm{s})(2 \pi \mathrm{rad} / \mathrm{rev})]^{2} \\
&=191 \mathrm{~J}.
\end{aligned} \nonumber\]
Discussion
In both parts, there is an impressive increase. First, the final angular velocity is large, although most world-class skaters can achieve spin rates about this great. Second, the final kinetic energy is much greater than the initial kinetic energy. The increase in rotational kinetic energy comes from work done by the skater in pulling in her arms. This work is internal work that depletes some of the skater’s food energy.
There are several other examples of objects that increase their rate of spin because something reduced their moment of inertia. Tornadoes are one example. Storm systems that create tornadoes are slowly rotating. When the radius of rotation narrows, even in a local region, angular velocity increases, sometimes to the furious level of a tornado. Earth is another example. Our planet was born from a huge cloud of gas and dust, the rotation of which came from turbulence in an even larger cloud. Gravitational forces caused the cloud to contract, and the rotation rate increased as a result. (See Figure \(\PageIndex{3}\).)
In case of human motion, one would not expect angular momentum to be conserved when a body interacts with the environment as its foot pushes off the ground. Astronauts floating in space aboard the International Space Station have no angular momentum relative to the inside of the ship if they are motionless. Their bodies will continue to have this zero value no matter how they twist about as long as they do not give themselves a push off the side of the vessel.
Exercise \(\PageIndex{1}\)
Is angular momentum completely analogous to linear momentum? What, if any, are their differences?
- Answer
-
Yes, angular and linear momentums are completely analogous. While they are exact analogs they have different units and are not directly inter-convertible like forms of energy are.
Section Summary
- Every rotational phenomenon has a direct translational analog , likewise angular momentum \(L\) can be defined as \(L=I \omega\).
- This equation is an analog to the definition of linear momentum as \(p=m v\). The relationship between torque and angular momentum is \(\text { net } \tau=\frac{\Delta L}{\Delta t}\).
- Angular momentum, like energy and linear momentum, is conserved. This universally applicable law is another sign of underlying unity in physical laws. Angular momentum is conserved when net external torque is zero, just as linear momentum is conserved when the net external force is zero.
Glossary
- rotational kinetic energy
- the kinetic energy due to the rotation of an object. This is part of its total kinetic energy


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agenda setting
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the identification of an issue or issues that require resolution and bringing these issues to the attention of community partners and concerned parties
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cost-benefit analysis
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analysis that compares the outcomes of the changes to the cost of implementing a policy
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cycle of poverty
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a series of events that occur between generations; once a person or family becomes impoverished, it is almost impossible to change their economic status, and external intervention is needed to break the cycle
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directly observed therapy (DOT)
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system in which medication is dispensed at a clinic or pharmacy to a client one dose at a time to ensure compliance for those who are at high risk for noncompliance (such as with clients who lack a permanent address)
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evidence-based practice policies
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policies developed from reliable data and statistics rather than intuition and personal opinion
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four spheres of political action in nursing
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the four areas in which nurses can effect change: workplace, government, community, and professional organizations
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Health in All Policies (HiAP)
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a collaborative approach to policy creation that integrates and articulates health considerations into policy development across sectors to improve the health of all communities and people
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health policy
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policies that describe a health goal and a way to accomplish it
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health policy process
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the steps or stages that are followed as a specific issue is identified and a plan of action intended to correct it is made
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health policymaking
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the formulation and establishment of policies and methods of achieving the policies by government bodies or other relevant organizations to address any of the varied aspects of health care, which includes public health and the health care system
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institutional policy
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rules that an organization has developed to govern the activities of anyone employed by or associated with the institution
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laws
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the system of rules by which a country or community regulates the behavior and actions of its members
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nursing policy
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sets goals and boundaries for nursing practice
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policy
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a course or principle of action adopted or proposed by a government, party, business, or individual
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policy adoption
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the acceptance or ratification of a policy
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policy development process
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the steps or stages that are followed as a specific problem or concern generates a plan of action intended to correct it
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policy evaluation
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determining how a policy is working and whether the intended outcomes are happening
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policy formulation
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creating a plan to solve a previously identified problem
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policy implementation
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the process of putting a new policy into effect through planning and funding
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preexisting conditions
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health problems diagnosed before an insurance policy goes into effect and will therefore not be covered under the new insurance policy
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public policy
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local, state, or national laws and regulations
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social capital
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resources accessed through social connections or networking that decrease barriers to health care
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social justice
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the fair and equal treatment of individuals
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social policy
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policy decisions that promote the general welfare of the public
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social support
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both actual and perceived assistance from one’s friends, acquaintances, coworkers, and family
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stage-sequential model
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a process that uses five steps to create a policy; these include agenda setting, policy formulation, policy adoption, policy implementation, and policy evaluation


8.2: Running MATLAB (Macintosh)
In order to run MATLAB on a Macintosh SE or PLUS computer, you need the program called EDU-MATLAB. The program requires at least 1 Mbyte of memory, System 3.0 or above, Finder version 3.0 or above, and an 800K drive. A hard disc drive is highly recommended. In order to run MATLAB on a Macintosh II, IIx, IIcx, or SE/30, you need the program called MacII-MATLAB, and the same system requirements apply.
To start MATLAB, you may need to open the folder containing the MATLAB program. Then just “double-click” the program icon or the program name (for example, EDU-MATLAB). Figure A.1 shows a typical organization of the folder containing Mac II-MATLAB. It contains the main program, the settings file, the demonstrations folder, and any toolbox folders. The double-click on Mac II-MATLAB produces the Command window as shown in Figure A.2. You will also see a Graph window partially hidden behind it. (The fact that the window is not in ffont means that it is opened but not currently active.) If you do not know what “clicking,” “dragging,” “pop-up menu,” and “trash” mean, you should stop reading now and familiarize yourself with the Macintosh.
In the command window, you should see the prompt \(\gg\). The program interpreter is waiting for you to enter instructions. At this point it is a good idea to run the demonstration programs that are available in the “About MATLAB” menu under the Apple menu. Just click on the “demos” button and select a demo. During pauses, strike any key to continue. Whenever you have a MATLAB file in any folder, then you may double-click the file to launch the program.
MATLAB has four types of windows:
- Command for computing, programming, and designing input/output displays;
- Graph for displaying plots and graphs;
- Edit for creating and modifying your own files; and
- Help for getting on-line help and for running demos.
All windows follow the traditional behavior of Macintosh windows. You can resize them (actually the help window has a fixed size) or move them. For more details on menus and windows, see the Macintosh and MATLAB manuals.


31.2: Fungal Forms, Nutrition, and Reproduction
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The word fungus comes from the Latin word for mushroom. Indeed, the familiar mushrooms are fungi, but there are many other types of fungi as well (Figure \(\PageIndex{1}\)). The kingdom Fungi includes an enormous variety of living organisms collectively referred to as Eumycota, or true fungi. While scientists have identified about 100,000 species of fungi, this is only a fraction of the over 1 million species likely present on Earth. Edible mushrooms, yeasts, black mold, and Penicillium notatum (the producer of the antibiotic penicillin) are all members of the kingdom Fungi, which belongs to the domain Eukarya. As eukaryotes, a typical fungal cell contains a true nucleus and many membrane-bound organelles.
Fungi were once considered plant-like organisms; however, DNA comparisons have shown that fungi are more closely related to animals than plants. Fungi are not capable of photosynthesis: They use complex organic compounds as sources of energy and carbon. Some fungal organisms multiply only asexually, whereas others undergo both asexual reproduction and sexual reproduction. Most fungi produce a large number of spores that are disseminated by the wind. Like bacteria, fungi play an essential role in ecosystems, because they are decomposers and participate in the cycling of nutrients by breaking down organic materials into simple molecules.
Fungi often interact with other organisms, forming mutually beneficial or mutualistic associations. Fungi also cause serious infections in plants and animals. For example, Dutch elm disease is a particularly devastating fungal infection that destroys many native species of elm ( Ulmus spp.). The fungus infects the vascular system of the tree. It was accidentally introduced to North America in the 1900s and decimated elm trees across the continent. Dutch elm disease is caused by the fungus Ophiostoma ulmi . The elm bark beetle acts as a vector and transmits the disease from tree to tree. Many European and Asiatic elms are less susceptible than American elms.
In humans, fungal infections are generally considered challenging to treat because, unlike bacteria, they do not respond to traditional antibiotic therapy since they are also eukaryotes. These infections may prove deadly for individuals with a compromised immune system.
Fungi have many commercial applications. The food industry uses yeasts in baking, brewing, and wine making. Many industrial compounds are byproducts of fungal fermentation. Fungi are the source of many commercial enzymes and antibiotics.
Cell Structure and Function
Fungi are eukaryotes and as such have a complex cellular organization. As eukaryotes, fungal cells contain a membrane-bound nucleus. A few types of fungi have structures comparable to the plasmids (loops of DNA) seen in bacteria. Fungal cells also contain mitochondria and a complex system of internal membranes, including the endoplasmic reticulum and Golgi apparatus.
Fungal cells do not have chloroplasts. Although the photosynthetic pigment chlorophyll is absent, many fungi display bright colors, ranging from red to green to black. The poisonous Amanita muscaria (fly agaric) is recognizable by its bright red cap with white patches (Figure \(\PageIndex{2}\)). Pigments in fungi are associated with the cell wall and play a protective role against ultraviolet radiation. Some pigments are toxic.
Like plant cells, fungal cells are surrounded by a thick cell wall; however, the rigid layers contain the complex polysaccharides chitin and glucan and not cellulose that is used by plants. Chitin, also found in the exoskeleton of insects, gives structural strength to the cell walls of fungi. The cell wall protects the cell from desiccation and predators. Fungi have plasma membranes similar to other eukaryotes, except that the structure is stabilized by ergosterol, a steroid molecule that functions like the cholesterol found in animal cell membranes. Most members of the kingdom Fungi are nonmotile. Flagella are produced only by the gametes in the primitive division Chytridiomycota.
Growth and Reproduction
The vegetative body of a fungus is called a thallus and can be unicellular or multicellular. Some fungi are dimorphic because they can go from being unicellular to multicellular depending on environmental conditions. Unicellular fungi are generally referred to as yeasts. Saccharomyces cerevisiae (baker’s yeast) and Candida species (the agents of thrush, a common fungal infection) are examples of unicellular fungi.
Most fungi are multicellular organisms. They display two distinct morphological stages: vegetative and reproductive. The vegetative stage is characterized by a tangle of slender thread-like structures called hyphae (singular, hypha), whereas the reproductive stage can be more conspicuous. A mass of hyphae is called a mycelium (Figure \(\PageIndex{3}\)). It can grow on a surface, in soil or decaying material, in a liquid, or even in or on living tissue. Although individual hypha must be observed under a microscope, the mycelium of a fungus can be very large with some species truly being “the fungus humongous.” The giant Armillaria ostoyae (honey mushroom) is considered the largest organism on Earth, spreading across over 2,000 acres of underground soil in eastern Oregon; it is estimated to be at least 2,400 years old.
Most fungal hyphae are divided into separate cells by end walls called septa (singular, septum). In most divisions (like plants, fungal phyla are called divisions by tradition) of fungi, tiny holes in the septa allow for the rapid flow of nutrients and small molecules from cell to cell along the hyphae. They are described as perforated septa. The hyphae in bread molds (which belong to the division Zygomycota) are not separated by septa. They are formed of large cells containing many nuclei, an arrangement described as coenocytic hyphae.
Fungi thrive in environments that are moist and slightly acidic, and can grow with or without light. They vary in their oxygen requirements. Most fungi are obligate aerobes, requiring oxygen to survive. Other species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes, meaning that they cannot grow and reproduce in an environment with oxygen. Yeasts are intermediate: They grow best in the presence of oxygen but can use fermentation in the absence of oxygen. The alcohol produced from yeast fermentation is used in wine and beer production, and the carbon dioxide they produce carbonates beer and sparkling wine, and makes bread rise.
Fungi can reproduce sexually or asexually. In both sexual and asexual reproduction, fungi produce spores that disperse from the parent organism by either floating in the wind or hitching a ride on an animal. Fungal spores are smaller and lighter than plant seeds, but they are not usually released as high in the air. The giant puffball mushroom bursts open and releases trillions of spores: The huge number of spores released increases the likelihood of spores landing in an environment that will support growth (Figure \(\PageIndex{4}\)).
How Fungi Obtain Nutrition
Like animals, fungi are heterotrophs: They use complex organic compounds as a source of carbon rather than fixing carbon dioxide from the atmosphere, as some bacteria and most plants do. In addition, fungi do not fix nitrogen from the atmosphere. Like animals, they must obtain it from their diet. However, unlike most animals that ingest food and then digest it internally in specialized organs, fungi perform these steps in the reverse order. Digestion precedes ingestion. First, exoenzymes, enzymes that catalyze reactions on compounds outside of the cell, are transported out of the hyphae where they break down nutrients in the environment. Then, the smaller molecules produced by the external digestion are absorbed through the large surface areas of the mycelium. As with animal cells, the fungal storage polysaccharide is glycogen rather than starch, as found in plants.
Fungi are mostly saprobes, organisms that derive nutrients from decaying organic matter. They obtain their nutrients from dead or decomposing organic matter, mainly plant material. Fungal exoenzymes are able to break down insoluble polysaccharides, such as the cellulose and lignin of dead wood, into readily absorbable glucose molecules. Decomposers are important components of ecosystems, because they return nutrients locked in dead bodies to a form that is usable for other organisms. This role is discussed in more detail later. Because of their varied metabolic pathways, fungi fulfill an important ecological role and are being investigated as potential tools in bioremediation. For example, some species of fungi can be used to break down diesel oil and polycyclic aromatic hydrocarbons. Other species take up heavy metals such as cadmium and lead.
Fungal Diversity
The kingdom Fungi contains four major divisions that were established according to their mode of sexual reproduction. Polyphyletic, unrelated fungi that reproduce without a sexual cycle, are placed for convenience in a fifth division, and a sixth major fungal group that does not fit well with any of the previous five has recently been described. Not all mycologists agree with this scheme. Rapid advances in molecular biology and the sequencing of 18S rRNA (a component of ribosomes) continue to reveal new and different relationships between the various categories of fungi.
The traditional divisions of Fungi are the Chytridiomycota (chytrids), the Zygomycota(conjugated fungi), the Ascomycota (sac fungi), and the Basidiomycota (club fungi). An older classification scheme grouped fungi that strictly use asexual reproduction into Deuteromycota, a group that is no longer in use. The Glomeromycota belong to a newly described group (Figure \(\PageIndex{5}\)).
Pathogenic Fungi
Many fungi have negative impacts on other species, including humans and the organisms they depend on for food. Fungi may be parasites, pathogens, and, in a very few cases, predators.
Plant Parasites and Pathogens
The production of enough good-quality crops is essential to our existence. Plant diseases have ruined crops, bringing widespread famine. Most plant pathogens are fungi that cause tissue decay and eventual death of the host (Figure \(\PageIndex{6}\)). In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Fungi are also responsible for food spoilage and the rotting of stored crops. For example, the fungus Claviceps purpurea causes ergot, a disease of cereal crops (especially of rye). Although the fungus reduces the yield of cereals, the effects of the ergot’s alkaloid toxins on humans and animals are of much greater significance: In animals, the disease is referred to as ergotism. The most common signs and symptoms are convulsions, hallucination, gangrene, and loss of milk in cattle. The active ingredient of ergot is lysergic acid, which is a precursor of the drug LSD. Smuts, rusts, and powdery or downy mildew are other examples of common fungal pathogens that affect crops.
Aflatoxins are toxic and carcinogenic compounds released by fungi of the genus Aspergillus . Periodically, harvests of nuts and grains are tainted by aflatoxins, leading to massive recall of produce, sometimes ruining producers, and causing food shortages in developing countries.
Animal and Human Parasites and Pathogens
Fungi can affect animals, including humans, in several ways. Fungi attack animals directly by colonizing and destroying tissues. Humans and other animals can be poisoned by eating toxic mushrooms or foods contaminated by fungi. In addition, individuals who display hypersensitivity to molds and spores develop strong and dangerous allergic reactions. Fungal infections are generally very difficult to treat because, unlike bacteria, fungi are eukaryotes. Antibiotics only target prokaryotic cells, whereas compounds that kill fungi also adversely affect the eukaryotic animal host.
Many fungal infections (mycoses) are superficial and termed cutaneous (meaning “skin”) mycoses. They are usually visible on the skin of the animal. Fungi that cause the superficial mycoses of the epidermis, hair, and nails rarely spread to the underlying tissue (Figure \(\PageIndex{7}\)). These fungi are often misnamed “dermatophytes” from the Greek dermis skin and phyte plant, but they are not plants. Dermatophytes are also called “ringworms” because of the red ring that they cause on skin (although the ring is caused by fungi, not a worm). These fungi secrete extracellular enzymes that break down keratin (a protein found in hair, skin, and nails), causing a number of conditions such as athlete’s foot, jock itch, and other cutaneous fungal infections. These conditions are usually treated with over-the-counter topical creams and powders, and are easily cleared. More persistent, superficial mycoses may require prescription oral medications.
Systemic mycoses spread to internal organs, most commonly entering the body through the respiratory system. For example, coccidioidomycosis (valley fever) is commonly found in the southwestern United States, where the fungus resides in the dust. Once inhaled, the spores develop in the lungs and cause signs and symptoms similar to those of tuberculosis. Histoplasmosis (Figure \(\PageIndex{7}\) c ) is caused by the dimorphic fungus Histoplasma capsulatum ; it causes pulmonary infections and, in rare cases, swelling of the membranes of the brain and spinal cord. Treatment of many fungal diseases requires the use of antifungal medications that have serious side effects.
Opportunistic mycoses are fungal infections that are either common in all environments or part of the normal biota. They affect mainly individuals who have a compromised immune system. Patients in the late stages of AIDS suffer from opportunistic mycoses, such as Pneumocystis , which can be life threatening. The yeast Candida spp., which is a common member of the natural biota, can grow unchecked if the pH, the immune defenses, or the normal population of bacteria is altered, causing yeast infections of the vagina or mouth (oral thrush).
Fungi may even take on a predatory lifestyle. In soil environments that are poor in nitrogen, some fungi resort to predation of nematodes (small roundworms). Species of Arthrobotrys fungi have a number of mechanisms to trap nematodes. For example, they have constricting rings within their network of hyphae. The rings swell when the nematode touches it and closes around the body of the nematode, thus trapping it. The fungus extends specialized hyphae that can penetrate the body of the worm and slowly digest the hapless prey.
Beneficial Fungi
Fungi play a crucial role in the balance of ecosystems. They colonize most habitats on Earth, preferring dark, moist conditions. They can thrive in seemingly hostile environments, such as the tundra, thanks to a most successful symbiosis with photosynthetic organisms, like lichens. Fungi are not obvious in the way that large animals or tall trees are. Yet, like bacteria, they are major decomposers of nature. With their versatile metabolism, fungi break down organic matter that is insoluble and would not be recycled otherwise.
Importance to Ecosystems
Food webs would be incomplete without organisms that decompose organic matter and fungi are key participants in this process. Decomposition allows for cycling of nutrients such as carbon, nitrogen, and phosphorus back into the environment so they are available to living things, rather than being trapped in dead organisms. Fungi are particularly important because they have evolved enzymes to break down cellulose and lignin, components of plant cell walls that few other organisms are able to digest, releasing their carbon content.
Fungi are also involved in ecologically important coevolved symbioses, both mutually beneficial and pathogenic with organisms from the other kingdoms. Mycorrhiza, a term combining the Greek roots myco meaning fungus and rhizo meaning root, refers to the association between vascular plant roots and their symbiotic fungi. Somewhere between 80–90 percent of all plant species have mycorrhizal partners. In a mycorrhizal association, the fungal mycelia use their extensive network of hyphae and large surface area in contact with the soil to channel water and minerals from the soil into the plant. In exchange, the plant supplies the products of photosynthesis to fuel the metabolism of the fungus. Ectomycorrhizae (“outside” mycorrhiza) depend on fungi enveloping the roots in a sheath (called a mantle) and a net of hyphae that extends into the roots between cells. In a second type, the Glomeromycota fungi form arbuscular mycorrhiza. In these mycorrhiza, the fungi form arbuscles, a specialized highly branched hypha, which penetrate root cells and are the sites of the metabolic exchanges between the fungus and the host plant. Orchids rely on a third type of mycorrhiza. Orchids form small seeds without much storage to sustain germination and growth. Their seeds will not germinate without a mycorrhizal partner (usually Basidiomycota). After nutrients in the seed are depleted, fungal symbionts support the growth of the orchid by providing necessary carbohydrates and minerals. Some orchids continue to be mycorrhizal throughout their lifecycle.
Lichens blanket many rocks and tree bark, displaying a range of colors and textures. Lichens are important pioneer organisms that colonize rock surfaces in otherwise lifeless environments such as are created by glacial recession. The lichen is able to leach nutrients from the rocks and break them down in the first step to creating soil. Lichens are also present in mature habitats on rock surfaces or the trunks of trees. They are an important food source for caribou. Lichens are not a single organism, but rather a fungus (usually an Ascomycota or Basidiomycota species) living in close contact with a photosynthetic organism (an alga or cyanobacterium). The body of a lichen, referred to as a thallus, is formed of hyphae wrapped around the green partner. The photosynthetic organism provides carbon and energy in the form of carbohydrates and receives protection from the elements by the thallus of the fungal partner. Some cyanobacteria fix nitrogen from the atmosphere, contributing nitrogenous compounds to the association. In return, the fungus supplies minerals and protection from dryness and excessive light by encasing the algae in its mycelium. The fungus also attaches the symbiotic organism to the substrate.
Fungi have evolved mutualistic associations with numerous arthropods. The association between species of Basidiomycota and scale insects is one example. The fungal mycelium covers and protects the insect colonies. The scale insects foster a flow of nutrients from the parasitized plant to the fungus. In a second example, leaf-cutting ants of Central and South America literally farm fungi. They cut disks of leaves from plants and pile them up in gardens. Fungi are cultivated in these gardens, digesting the cellulose that the ants cannot break down. Once smaller sugar molecules are produced and consumed by the fungi, they in turn become a meal for the ants. The insects also patrol their garden, preying on competing fungi. Both ants and fungi benefit from the association. The fungus receives a steady supply of leaves and freedom from competition, while the ants feed on the fungi they cultivate.
Importance to Humans
Although we often think of fungi as organisms that cause diseases and rot food, fungi are important to human life on many levels. As we have seen, they influence the well-being of human populations on a large scale because they help nutrients cycle in ecosystems. They have other ecosystem roles as well. For example, as animal pathogens, fungi help to control the population of damaging pests. These fungi are very specific to the insects they attack and do not infect other animals or plants. The potential to use fungi as microbial insecticides is being investigated, with several species already on the market. For example, the fungus Beauveria bassiana is a pesticide that is currently being tested as a possible biological control for the recent spread of emerald ash borer. It has been released in Michigan, Illinois, Indiana, Ohio, West Virginia, and Maryland.
The mycorrhizal relationship between fungi and plant roots is essential for the productivity of farmland. Without the fungal partner in the root systems, 80–90% of trees and grasses would not survive. Mycorrhizal fungal inoculants are available as soil amendments from gardening supply stores and promoted by supporters of organic agriculture.
We also eat some types of fungi. Mushrooms figure prominently in the human diet. Morels, shiitake mushrooms, chanterelles, and truffles are considered delicacies (Figure \(\PageIndex{8}\)). The humble meadow mushroom, Agaricus campestris , appears in many dishes. Molds of the genus Penicillium ripen many cheeses. They originate in the natural environment such as the caves of Roquefort, France, where wheels of sheep milk cheese are stacked to capture the molds responsible for the blue veins and pungent taste of the cheese.
Fermentation—of grains to produce beer, and of fruits to produce wine—is an ancient art that humans in most cultures have practiced for millennia. Wild yeasts are acquired from the environment and used to ferment sugars into CO 2 and ethyl alcohol under anaerobic conditions. It is now possible to purchase isolated strains of wild yeasts from different wine-making regions. Pasteur was instrumental in developing a reliable strain of brewer’s yeast, Saccharomyces cerevisiae , for the French brewing industry in the late 1850s. It was one of the first examples of biotechnology patenting. Yeast is also used to make breads that rise. The carbon dioxide they produce is responsible for the bubbles produced in the dough that become the air pockets of the baked bread.
Many secondary metabolites of fungi are of great commercial importance. Antibiotics are naturally produced by fungi to kill or inhibit the growth of bacteria, and limit competition in the natural environment. Valuable drugs isolated from fungi include the immunosuppressant drug cyclosporine (which reduces the risk of rejection after organ transplant), the precursors of steroid hormones, and ergot alkaloids used to stop bleeding. In addition, as easily cultured eukaryotic organisms, some fungi are important model research organisms including the red bread mold Neurospora crassa and the yeast, S . cerevisiae.
Section Summary
Fungi are eukaryotic organisms that appeared on land over 450 million years ago. They are heterotrophs and contain neither photosynthetic pigments such as chlorophylls nor organelles such as chloroplasts. Because they feed on decaying and dead matter, they are saprobes. Fungi are important decomposers and release essential elements into the environment. External enzymes digest nutrients that are absorbed by the body of the fungus called a thallus. A thick cell wall made of chitin surrounds the cell. Fungi can be unicellular as yeasts or develop a network of filaments called a mycelium, often described as mold. Most species multiply by asexual and sexual reproductive cycles, and display an alternation of generations.
The divisions of fungi are the Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota, and Glomeromycota.
Fungi establish parasitic relationships with plants and animals. Fungal diseases can decimate crops and spoil food during storage. Compounds produced by fungi can be toxic to humans and other animals. Mycoses are infections caused by fungi. Superficial mycoses affect the skin, whereas systemic mycoses spread through the body. Fungal infections are difficult to cure.
Fungi have colonized all environments on Earth but are most often found in cool, dark, moist places with a supply of decaying material. Fungi are important decomposers because they are saprobes. Many successful mutualistic relationships involve a fungus and another organism. They establish complex mycorrhizal associations with the roots of plants.
Fungi are important to everyday human life. Fungi are important decomposers in most ecosystems. Mycorrhizal fungi are essential for the growth of most plants. Fungi, as food, play a role in human nutrition in the form of mushrooms and as agents of fermentation in the production of bread, cheeses, alcoholic beverages, and numerous other food preparations. Secondary metabolites of fungi are used in medicine as antibiotics and anticoagulants. Fungi are used in research as model organisms for the study of eukaryotic genetics and metabolism.
Glossary
- Ascomycota
- (sac fungi) a division of fungi that store spores in a sac called ascus
- basidiomycota
- (club fungi) a division of fungi that produce club shaped structures, basidia, which contain spores
- Chytridiomycota
- (chytrids) a primitive division of fungi that live in water and produce gametes with flagella
- Glomeromycota
- a group of fungi that form symbiotic relationships with the roots of trees
- hypha
- a fungal filament composed of one or more cells
- lichen
- the close association of a fungus with a photosynthetic alga or bacterium that benefits both partners
- mold
- a tangle of visible mycelia with a fuzzy appearance
- mycelium
- a mass of fungal hyphae
- mycorrhiza
- a mutualistic association between fungi and vascular plant roots
- mycosis
- a fungal infection
- septum
- the cell wall division between hyphae
- thallus
- a vegetative body of a fungus
- yeast
- a general term used to describe unicellular fungi
- Zygomycota
- (conjugated fungi) the division of fungi that form a zygote contained in a zygospore
Contributors and Attributions
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Samantha Fowler (Clayton State University), Rebecca Roush (Sandhills Community College), James Wise (Hampton University). Original content by OpenStax (CC BY 4.0; Access for free at https://cnx.org/contents/b3c1e1d2-83...4-e119a8aafbdd ).


11.4: The Competitive World of Retailing
What are the Different Kinds of Retail Operations?
Some 15 million Americans are engaged in retailing. Of this number, almost half work in service businesses such as barbershops, lawyers’ offices, and amusement parks. Although most retailers are involved in small businesses, most sales are made by the giant retail organizations, such as Walmart, Target, and Macy’s. Half of all retail sales come from fewer than 10 percent of all retail businesses. This small group employs about 40 percent of all retail workers. Retailers feel the impact of changes in the economy more than many other types of businesses. Survival depends on keeping up with changing lifestyles and customer shopping patterns. In recent years, online retailing trends have significantly impacted retailing organizations, providing more opportunity for smaller retailers and more competition for larger retailers.
Types of Retail Operations
There is a great deal of variety in retail operations. The major types of retailers are described in Table 11.4.1, which divides them into two main categories: in-store and non-store retailing. Examples of in-store retailing include Walmart, Target, Macy’s, and Neiman Marcus. These retailers get most of their revenue from people who come to the store to buy what they want. Many in-store retailers also do some catalog and telephone sales.
Table \(\PageIndex{1}\): Retailing Takes Many Forms
| Types of In-Store Retailing | Description | Examples |
|---|---|---|
| Department store | Houses many departments under one roof with each treated as a separate buying center to achieve economies of buying, promotion, and control | Macy’s, Nordstrom, Bloomingdale’s, Kohl’s |
| Specialty store | Specializes in a category of merchandise and carries a complete assortment | Toys “R” Us, Zales Jewelers |
| Convenience store | Offers convenience goods with long store hours and quick checkout | 7-Eleven, Circle K |
| Supermarket | Specializes in a wide assortment of food, with self-service | Safeway, Kroger, Winn-Dixie |
| Discount store | Competes on the basis of low prices and high turnover; offers few services | Walmart, Target |
| Off-price retailer | Sells at prices 25 percent or more below traditional department store prices in a spartan environment | TJ Maxx, HomeGoods |
| Factory outlet | Owned by manufacturer; sells closeouts, factory seconds, and canceled orders | Levi Strauss, Dansk |
| Catalog store | Sends catalogs to customers and displays merchandise in showrooms where customers can order from attached warehouse | Ikea |
| Types of Non-store Retailing | Description | Examples |
| Vending machine | Sells merchandise by machine | Canteen |
| Direct selling | Sells face-to-face, usually in the person’s home | Avon, Amway |
| Direct-response marketing | Attempts to get immediate consumer sale through media advertising, catalogs, pop-up ads, or direct mail | K-Tel Music, Ronco |
| Home shopping networks | Selling via cable television | Home Shopping Network, QVC |
| Internet retailing (e-retailing) | Selling over the internet | Bluefly.com, landsend.com, gap.com, Amazon.com, Wayfair.com, Dell.com |
Non-store retailing includes vending, direct selling, direct-response marketing, home shopping networks, and internet retailing. Vending uses machines to sell food and other items, usually as a convenience in institutions such as schools and hospitals.
Atmosphere and Retail Image
In considering retailing as a distribution strategy (place in the 5Ps), it is important to understand that place includes more than channel members or logistics. It also includes atmospherics—the image of the actual retailing store (or, in the case of non-store retailing, the platform from which the product is offered, such as a website or vending machine). An important task in retailing is to create this image. Marketers combine the store’s merchandise mix, service level, and atmosphere to make up a retail image. Atmosphere refers to the physical layout and décor of the store. They can create a relaxed or busy feeling, a sense of luxury, a friendly or cold attitude, and a sense of organization or clutter.
These are the most influential factors in creating a store’s atmosphere:
- Employee type and density: Employee type refers to an employee’s general characteristics—for instance, neat, friendly, knowledgeable, or service-oriented. Density is the number of employees per 1,000 square feet of selling space. A discount retailer such as Target has a low employee density that creates a “do-it-yourself” casual atmosphere.
- Merchandise type and density: The type of merchandise carried and how it is displayed add to the atmosphere the retailer is trying to create. A prestigious retailer such as Saks or Nordstrom carries the best brand names and displays them in a neat, uncluttered arrangement. Other retailers such as Dollar Tree may display goods in a more cluttered, crowded, disheveled way because their target market (lower-income individuals) equates clutter with open markets (and with lower prices and “deals”).
- Fixture type and density: Fixtures can be elegant (rich woods) or trendy (chrome and smoked glass), or they can be old, beat-up tables, as in an antique store. The fixtures should be consistent with the general atmosphere the store is trying to create. By displaying its merchandise on tables and shelves rather than on traditional pipe racks, the Gap creates a relaxed and uncluttered atmosphere that enables customers to see and touch the merchandise more easily. In addition to traditional display racks, Cabela’s retail stores feature two 5,000-gallon aquariums stocked with carp, trout, and other fish and a diorama featuring elephants, lions, zebras, hyenas, and other animals. A typical Cabela’s has several million customers a year. It is not unusual for someone to drive many miles to get to a Cabela’s, where you can often see license plates from many states and Canadian provinces.
- Sound: Sound can be pleasant or unpleasant for a customer. Classical music at a nice Italian restaurant helps create ambiance, just as country and western music does at a truck stop. Music can also entice customers to stay in the store longer and buy more, or it can encourage them to eat quickly and leave a table for others.
- Odors: Smell can either stimulate or detract from sales. The wonderful smell of pastries and breads entices bakery customers, as does the smell of freshly brewed coffee in a shopping mall. Conversely, customers can be repulsed by bad odors, such as cigarette smoke, musty smells, antiseptic odors, and overly powerful room deodorizers.
EXPANDING AROUND THE GLOBE
Creative Retailing at Selfridges
To steer traffic to its flagship store in London, Selfridges sought divine intervention—that is, a 50-foot statue of Jesus. The small-scale replica of Rio de Janeiro’s famous monument gazed down on shoppers during a month-long Brazilian-themed promotion.
Combined with a radical redesign of the retail space that makes each of Selfridges’ four outlets feel more like a collection of quirky boutiques than one gargantuan marketplace, stunts like the Brazil 40° celebration have transformed the once-staid 95-year-old British retail chain into a premier arbiter of hip. Selfridges’ success has spurred retailers worldwide to take a closer look. “A department store chief who has not made his way to Selfridges to study its operation,” says Arnold Aronson, former CEO of Saks Fifth Avenue, “is an executive not doing his job.”
Typically, department stores develop their own merchandising strategies, resulting in a retail space crowded with Tommy Hilfiger, Ralph Lauren, and other predictable names arranged in displays that rarely vary from one chain to the next. Selfridges, however, operates on the theory that no one understands a product better than the designer or vendor that created it. So individual designers are allotted space in Selfridges and asked to create in-store displays that highlight their work. Traditional “departments” such as shoes, cosmetics, and men’s business wear have been organized by lifestyle—youth, sports, or women’s contemporary. This helps expose customers to merchandise they might not otherwise see.
Recently, Selfridges asked a tattoo and body-piercing parlor called Metal Morphosis to set up shop next to some women’s fashion vendors. Metal Morphosis was such a huge hit with shoppers en route to the clothing racks that it will soon expand to other Selfridges outlets.
Selfridges is also known for its “happenings.” They recently opened a low-cost interfaith charity shop within the confines of their luxury brand Oxford street store in London. Performance artist Miranda July was involved in the creation of this shop-within-a-shop, which partners with Islamic, Jewish, and other faith groups to promote the charity store. Ironically, shoppers can find bargain-priced donated blouses just feet away from some priced at over $3,000.
Critical Thinking Questions
- Selfridges opened a new store described as a “silver blob” or “spaceship.” The building has no straight lines and is covered with 15,000 anodized aluminum disks. The atrium is an array of high-gloss white elevators and balconies that are all slanted to avoid “the atrium look.” Do you think Selfridges is becoming too cool or hip? What impact will this have on sales?
- Would Selfridges be successful in the United States? Why or why not?
CONCEPT CHECK
- Describe at least five types of in-store retailing and four forms of non-store retailing.
- What factors most influence a retail store’s atmosphere?


17.1: Prelude to Sound
Sound is an example of a mechanical wave, specifically, a pressure wave: Sound waves travel through the air and other media as oscillations of molecules. Normal human hearing encompasses an impressive range of frequencies from 20 Hz to 20 kHz. Sounds below 20 Hz are called infrasound, whereas those above 20 kHz are called ultrasound. Some animals, like the bat shown in Figure 17.1, can hear sounds in the ultrasonic range.
Many of the concepts covered in Waves also have applications in the study of sound. For example, when a sound wave encounters an interface between two media with different wave speeds, reflection and transmission of the wave occur.
Ultrasound has many uses in science, engineering, and medicine. Ultrasound is used for nondestructive testing in engineering, such as testing the thickness of coating on metal. In medicine, sound waves are far less destructive than X-rays and can be used to image the fetus in a mother’s womb without danger to the fetus or the mother. Later in this chapter, we discuss the Doppler effect, which can be used to determine the velocity of blood in the arteries or wind speed in weather systems.


2.0: Dream of the Rood- Background
The Dream of the Rood is one of the earliest Christian poems in the corpus of Old English literature and an example of the genre of dream poetry. Like most Old English poetry, it is written in alliterative verse. Rood is from the Old English word rod ‘pole’, or more specifically ‘crucifix’. Preserved in the 10th century Vercelli Book, the poem may be considerably older, even one of the oldest works of Old English literature.
Background information
A part of The Dream of the Rood can be found on the 8th century Ruthwell Cross, which was an 18 feet (5.5 m), free standing Anglo-Saxon cross that was perhaps intended as a ‘conversion tool’. At each side of the vine-tracery are carved runes. On the cross there is an excerpt that was written in runes along with scenes of Jesus healing the blind, the Annunciation and the story of Egypt. Although it was torn down and destroyed during a Protestant revolt, it was reconstructed as much as possible after the fear of iconography passed. Fortunately during that time of religious unrest, those words that were in the runes were still protected in the Vercelli Book , so called because the book is kept in the Italian city of Vercelli. The Vercelli Book , which can be dated to the 10th century, includes twenty-three homilies interspersed with six poems: The Dream of the Rood , Andreas , The Fates of the Apostles , Soul and Body , Elene and a poetic, homiletic fragment.
Possible authorship
The author of Dream of the Rood is unknown, but by knowing the approximate date of the Ruthwell Cross, scholars have been able to suggest possible authors. These include the Anglo-Saxon poets Cædmon and Cynewulf.
The Poem
The poem is set up with the narrator having a dream. In this dream or vision he is speaking to the Cross on which Jesus was crucified. The poem itself is divided up into three separate sections: the first part (ll. 1–27), the second part (ll. 28–121) and the third part (ll. 122–156). In section one, the narrator has a vision of the Cross. Initially when the dreamer sees the Cross, he notes how it is covered with gems. He is aware of how wretched he is compared to how glorious the tree is. However, he comes to see that amidst the beautiful stones it is stained with blood. In section two, the Cross shares its account of Jesus’ death. The Crucifixion story is told from the perspective of the Cross. It begins with the enemy coming to cut the tree down and carrying it away. The tree learns that it is not to be the bearer of a criminal, but instead Christ crucified. The Lord and the Cross become one, and they stand together as victors, refusing to fall, taking on insurmountable pain for the sake of mankind. It is not just Christ, but the Cross as well that is pierced with nails. Adelhied L. J. Thieme remarks, “The cross itself is portrayed as his lord’s retainer whose most outstanding characteristic is that of unwavering loyalty”. The Rood and Christ are one in the portrayal of the Passion—they are both pierced with nails, mocked and tortured. Then, just as with Christ, the Cross is resurrected, and adorned with gold and silver. It is honoured above all trees just as Jesus is honoured above all men. The Cross then charges the visionary to share all that he has seen with others. In section three, the author gives his reflections about this vision. The vision ends, and the man is left with his thoughts. He gives praise to God for what he has seen and is filled with hope for eternal life and his desire to once again be near the glorious Cross.
Additional information on “Dream of the Rood” can be found here.
- Dream of the Rood. Provided by : Wikipedia. Located at : https://en.Wikipedia.org/wiki/Dream_of_the_Rood . License : CC BY-SA: Attribution-ShareAlike