4.6: Moving Objects, Spectra, and the Doppler Effect
The
Doppler Effect
is a change in an object’s spectrum because the object is moving closer or away from the observer. In
sound
we experience this change in a siren’s pitch. When it approaches us, the waves are being compressed, then becoming longer as it moves away. This increase in pitch can be heard as a police car approaches and then decreases as it moves farther away.
What are the Implications of Doppler Shift?
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What are The Astronomical Implications and Importance of Spectra?

- From the star’s spectra
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How do we know if an object, star, galaxy, etc., is moving towards or away from us?
- Look for a red or blue shift in the object’s spectra
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Can we tell how fast an object is moving towards or away from us?
- Yes, by the extent of red or blue shift
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How do we know what a star is made up of?
Consider this…
For most of history, visible light was the single most recognized portion of the electromagnetic spectrum, EMS. The ancient Greeks noted that light traveled in straight lines and studied its properties. Over the years the study of light continued. During the 16th and 17th centuries there were conflicting theories which regarded light as either a wave or a particle. In 1800, astronomer Frederick William Herschel discovered infrared radiation while using a thermometer to measure temperatures of visible light frequencies. A year later Johann Ritter discovered ultraviolet radiation.


9.1: Analyzing Poetry
This resource created by Jonathan Sircy, Department of English, Charleston Southern University.
What is poetry?
We can distinguish poetry from prose by its
- preference for formal organization,
- intensely conveyed emotions and images,
- and concentrated use of language.
Poetry favors the concrete and particular over the vague and abstract. Poetic language isn’t disconnected from normal communication. Rather, it conveys ideas and emotions with greater precision than everyday language.
How can we analyze poetry?
There are several ways to skin the poetic cat. What follows are four large categories with accompanying questions that can help us systematically interpret a poem. Not only are these categories not mutually exclusive, they are often complementary.
STRUCTURE
If we pay attention to a particular poem’s meter, tone, imagery, and figurative language, we are able to talk about a poem’s unity . This attention to structure starts from the premise that each of the poem’s parts work together organically (rather than, say, mechanically) to achieve a unified goal. If we were to put that goal into a single sentence, we would have the poem’s theme , a succinct statement of the poem’s central idea and emotions.
Chief question: What idea or emotion UNIFIES the poem’s different parts?
Key terms: meter, tone, imagery, figurative language
Meter
: the pattern of accented and unaccented syllables in a given poetic line
Tone
: the speaker’s attitude toward his subject, audience, or himself
Imagery
: the poetic representation of any sense experience
Figurative language
: the non-literal use of language to achieve an effect
HISTORICAL CONTEXT
When we pay attention to a poem’s structure, we pretend that it is an artifact that can be separated from the outside world. But every literary work had an author and an audience, and both are deeply influenced by a particular place and time. This not only affects the way we read poetic allusions but the way we interpret particular words.
Chief Question: How do the poem’s words reflect the cultural context of the author and/or poet?
INTERTEXTUALITY
Poems aren’t just in conversation with history. They’re in conversation with other poems. This means that a literary work—in its form and/or content—resembles other literary works. When we focus on formal similarities, we’re concerned with genres, the different types or subcategories a poet has chosen (e.g. epic, lyric, satire). When we focus on similar content, we are either discussing allusions —intended references to another literary image—or archetypes , images or characters that appear so frequently they are less the domain of one author than part of a common literary heritage.
Chief question: How is this literary work like/unlike other literary works?
ETHICS
Every poem interprets life and thus, explicitly or implicitly, provides us with a view of the world. Defenders of poetry have long maintained that poetry is uniquely able to delight AND instruct; in fact, it often instructs BY delighting. That means every literary work presents actions/beliefs for us to applaud or denounce. This is often the most difficult thing to interpret about a particular work of art, and we must keep in mind that a work may present objectionable actions or beliefs in order to criticize them.
Chief question: What actions or beliefs does the poem support?


7.13D: Synthesizing DNA
- Outline the methods and uses of DNA synthesis
To understand bacterial genetics, the underlying genetic material (i.e. DNA) must be understood. DNA must be synthesized to study genes, the sequence of genomes, and many other studies. This occurs in two fashions, by polymerase chain reaction (PCR) which is enzymatic and chemical synthesis. PCR is covered in another atom. Here we will focus on chemical synthesis of DNA, which is also known as oligonucleotide synthesis.
Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids, both DNA and RNA with a defined chemical structure (sequence). The technique is extremely useful in current laboratory practice because it provides a rapid and inexpensive access to custom-made oligonucleotides of the desired sequence. Whereas enzymes synthesize DNA and RNA in a 5′ to 3′ direction, chemical oligonucleotide synthesis is carried out in the opposite, 3′ to 5′ direction.
Currently, the process is implemented as solid -phase synthesis using phosphoramidite method and phosphoramidite building blocks derived from protected 2′-deoxynucleosides (dA, dC, dG, and T), ribonucleosides (A, C, G, and U), or chemically modified nucleosides, e.g. LNA. To obtain the desired oligonucleotide, the building blocks are sequentially coupled to the growing oligonucleotide chain in the order required by the sequence of the product. The process has been fully automated since the late 1970’s. Upon the completion of the chain assembly, the product is released from the solid phase to solution, deprotected, and collected. The occurrence of side reactions sets practical limits for the length of synthetic oligonucleotides (up to about 200 nucleotide residues) because the number of errors accumulates with the length of the oligonucleotide being synthesized. Products are often isolated by HPLC to obtain the desired oligonucleotides in high purity. Typically, synthetic oligonucleotides are single-stranded DNA or RNA molecules around 15–25 bases in length. Oligonucleotides find a variety of applications in molecular biology and medicine. They are most commonly used as antisense oligonucleotides, small interfering RNA, primers for DNA sequencing and amplification, probes for detecting complementary DNA or RNA via molecular hybridization, tools for the targeted introduction of mutations and restriction sites, and for the synthesis of artificial genes.
A further application of oligosynthesis is to make artificial genes. Artificial gene synthesis is the process of synthesizing a gene in vitro without the need for initial template DNA samples. The main method is currently by oligonucleotide synthesis (also used for other applications) from digital genetic sequences and subsequent annealing of the resultant fragments. In contrast, natural DNA replication requires existing DNA templates for synthesizing new DNA.
Key Points
- DNA and RNA are at their essence chemical structures, and as such complex chemical reactions can be used to synthesize them.
- There are enzymatic ways to amplify DNA, notably PCR, while DNA sequences can be chemically synthesized by a process known as oligosynthesis.
- Oligosynthesis can be used to make artificial genes, which allows scientists to design and synthesis novel gene products, without relying a template of a gene found in nature.
Key Terms
- phosphoramidite : Any of a class of organic compounds formally derived from a phosphite by replacing a >P-O-R with a >P-N<R2 group; used in the synthesis of nucleic acids, etc.
- HPLC : High-performance liquid chromatography (sometimes referred to as high-pressure liquid chromatography), HPLC, is a chromatographic technique used to separate a mixture of compounds in analytical chemistry and biochemistry with the purpose of identifying, quantifying and purifying the individual components of the mixture.


3.2: Solving a Formula for a Variable (Rewriting a Formula)
In the Water Industry, we use lots of formulas for computing area, volume, pressure, cost, and so much more. Sometimes, we need to rewrite a formula in terms of a different quantity.
When solving a formula for a particular variable, it is sometimes helpful to place a rectangle or a circle around the variable you are isolating since formulas contain many variables and we may lose our focus as to which variable we are isolating. We will proceed as we did for solving linear equations by “undoing” operations to isolate the variable.
The volume of a rectangular tank is given by \(V=LWH\), rewrite the formula by solving for \(H\).
Solution
To “undo” the multiplication of H by LW, we divide both sides of the equation by LW to obtain:
\[\frac{V}{ \boldsymbol{LW}}=\frac{LWH}{ \boldsymbol{ LW}}\]
\[{V}\over {LW}=H\]
The filtration rate is defined as Filtration Rate \(=\frac{Flow}{Surface \, \, Area}\). Solve this equation for the Surface Area.
Solution
Step 1: Multiply both sides of the equation by Surface Area (to remove the Surface Area from the denominator. In other words, we cannot isolate Surface Area until it is no longer in the denominator)
\[\left(Filtration\,\, Rate\right)\cdot \left(\boldsymbol{Surface\,\, Area}\right) =\frac{Flow}{Surface\,\, Area}\cdot \left(\boldsymbol{Surface\,\, Area}\right)\]
\[\left(Filtration\,\, Rate\right) \cdot \left(Surface\,\, Area\right) =Flow\]
Step 2: Isolate the Surface Area by dividing both sides by Filtration Rate
\[\frac{\left( Filtration\,\, Rate\right)\cdot \left(Surface\,\, Area\right) }{(\boldsymbol{Filtration\,\, Rate})}=\frac{Flow}{(\boldsymbol{Filtration\,\, Rate})} \]
\[Surface\,\, Area=\frac{Flow}{Filtration\,\, Rate}\]
This is helpful if we need to calculate the Surface Area and we are given the flow and the filtration rate.


6.4: Design Principles for Developing Learning Materials for Emerging Technologies
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In developing learning materials for any technology, learning theories must be used for effective and efficient instruction. This section will address theories and design principles for emerging technologies.
Early learning materials development was influenced by behaviourist learning theory. Behaviourists claim that it is the observable behaviour of the learner that indicates whether or not they have learned, not what is going on in the learner’s head. Early instructional methods, such as the teaching machine, were influenced by behaviourist theory. The teaching machine taught by drill and practice, and transferred the repetitiveness of teaching from the instructors to the machine.
Cognitive learning theory influenced the development of learning materials with the introduction of computer-based instruction. Cognitive psychologists see learning as a process involving the use of memory, motivation, and thinking, and that reflection plays an important part in learning. Cognitivists perceive learning as an internal process and claim that the amount learned depends on the processing capacity of the learner, the amount of effort expended during the learning process, the quality of the processing, and the learner’s existing knowledge structure. Cognitive theory was influenced by information processing theory, which proposes that learners use different types of memory during learning.
As technology emerged, there was more emphasis on learner-centred education, which promoted the use of constructivist theory in the development of learning materials. Constructivists claimed that learners interpret information and the world according to their personal reality, and that they learn by observation, processing, and interpretation, and then personalize the information into their own worldview. Also, learners learn best when they can contextualize what they learn for immediate application and to acquire personal meaning. The learner-centred approach allows learners to develop problem-solving skills and learn by doing rather than by being told.
They are many instructional design models for developing learning materials. Dick et al. (2001) proposed a design model with the major components being design, development, implementation, and evaluation of instruction. Another widely used model is by Gagné et al. (1991) who claimed that strategies for learning should be based on learning outcomes. Gagné specifies nine types of instructional events:
- gain the learner’s attention;
- inform the learner of the lesson objectives;
- stimulate recall of prior knowledge;
- present stimuli with distinctive features to aid in perception;
- guide learning to promote semantic encoding;
- elicit performance;
- provide informative feedback;
- assess performance; and
- enhance retention and learning transfer.
Most of the current and past instructional design models were developed for classroom and print-based instruction rather than for learner-centred instruction and e-learning. New instructional design models are needed to develop learning materials for delivery on emerging technologies.
According to Jacobs and Dempsey (2002), some emerging influences that will affect future instructional design include object-oriented distributed learning environments, the use of artificial intelligence techniques, cognitive science, and neuroscience. Below are guidelines for educators to develop learning materials for delivery via emerging technologies.
Tips and Guidelines
- Information should be developed in “chunks” to facilitate processing in working memory since humans have limited working memory capacity. Chunking is important for mobile technologies that have small display screens, such as cell phones, PDAs, etc.
- Content should be broken down into learning objects to allow learners to access segments of learning materials to meet their learning needs. A learning object is defined as any digital resource that can be re-used to achieve a specific learning outcome (Ally, 2004b). Learning materials for emerging technologies should be developed in the form of information objects, which are then assembled to form learning objects for lessons. A learning session using a mobile device can be seen as consisting of a number of information objects sequenced in a pre-determined way, or sequenced, according to the user’s needs. The learning object approach is helpful where learners will access learning materials just in time, as they complete projects using a self-directed, experiential approach. Also, learning objects allow for instant assembly of learning materials by learners and by intelligent software agents to meet learners’ needs.
- Use the constructivist approach to learning to allow learners to explore and personalize the materials during the learning process. Learning should be project-based to allow learners to experience the world by doing things, rather than passively receiving information, to build things, to think critically, and to develop problem-solving skills (Page, 2006). Mobile technologies facilitate project-based learning since learners can learn in their own time and in their own environments. For example, as learners complete a project they can use wireless mobile technology to access just in time information and the instructor as needed.
- Simple interfaces prevent cognitive overload. For example, graphic outlines can be used as interfaces and as navigational tools for learners. The interface should allow the learner to access learning materials with minimal effort and navigate with ease. This is critical for emerging technologies since some output devices are small.
- Use active learning strategies that allow learners to summarize what they learn and to develop critical thinking skills. For example, learners can be asked to generate a concept map to summarize what they learned. A concept map or a network diagram can show the important concepts in a lesson and the relationship between them. Learner-generated concept maps allow learners to process information at a high level. High-level concept maps and networks can represent information spatially, so learners can see the main ideas and their relationships.
- Learning materials should be presented so that information can be transferred from the senses to the sensory store, and then to working memory. The amount of information transferred to working memory depends on the importance assigned to the incoming information and whether existing cognitive structures can make sense of the information. Strategies that check whether learners have the appropriate existing cognitive structures to process the information should be used in emerging technologies delivery. Pre-instructional strategies, such as advance organizers and overviews, should be used if relevant cognitive structures do not exist.
- There should be a variety of learning strategies to accommodate individual differences. Different learners will perceive, interact with, and respond to the learning environment in different ways, based on their learning styles (Kolb, 1984).
According to Kolb, there are four learning style types:
- Divergers are learners who have good people skills. When working in groups, they try to cultivate harmony to assure that everyone works together smoothly.
- Assimilators like to work with details, and are reflective and relatively passive during the learning process.
- Convergers prefer to experiment with, and apply new knowledge and skills, often by trial and error.
- Accommodators are risk-takers, who want to apply immediately what they learn to real-life problems or situations.
Examples of strategies to cater for individual learning preferences include:
- Use visuals at the start of a lesson to present the big picture, before going into the details of the information.
- For the active learners, strategies should provide the opportunity to immediately apply the knowledge.
- To encourage creativity, there must be opportunities to apply what was learned in real-life situations so that learners can go beyond what was presented.
- The use of emerging technologies will make it easier to cater to learners’ individual differences by determining preferences, and using the appropriate learning strategy based on those preferences.
- Provide learners the opportunity to use their meta-cognitive skills during the learning process. Meta-cognition is a learner’s ability to be aware of their cognitive capabilities and to use these capabilities to learn. This is critical in e-learning, since learners will complete the learning materials individually. Exercises with feedback throughout a lesson are good strategies to allow learners to check their progress, and to adjust their learning approach as necessary.
- Learners should be allowed to construct knowledge, rather than passively receive knowledge through instruction. Constructivists view learning as the result of mental construction where learners learn by integrating new information with what they already know.
- Learners should be given the opportunity to reflect on what they are learning and to internalize the information. There should be embedded questions throughout the learning session to encourage learners to reflect on, and process the information in a relevant and meaningful manner. Learners can be asked to generate a journal to encourage reflection and processing. Interactive learning promotes higher-level learning and social presence, and personal meaning (Heinich et al., 2002).
Intelligent agents should be embedded in the technology to design instruction and deliver the instruction based on individual learner needs. An intelligent agent gathers information about learners and them respond based on the what was learned about the student. For example, if a learner consistently gets a question on a concept wrong, the intelligent agent will prescribe other learning strategies until the learner master the concept. As the user interacts with the system, the agent learns more about the learner. This is critical, as learning materials may be accessed by people globally. These agents can be proactive so that they can recognize and react to changes in the learning process. As the intelligent agent interacts with the learner, it gains more experience by learning about the learner and then determining the difficulty of materials to present, the most appropriate learning strategy based on the learner’s style, and the sequence of the instruction (Ally, 2002). The intelligent learning system should reason about a learner’s knowledge, monitor progress, and adapt the teaching strategy to individual’s learning pattern (Woolf, 1987). For example, the intelligent system could monitor learning and build a best practice database for different learning styles. It could also track common errors and prescribe strategies to prevent similar errors in the future.


24.4: Lipid Metabolism
By the end of this section, you will be able to:
- Explain how energy can be derived from fat
- Explain the purpose and process of ketogenesis
- Describe the process of ketone body oxidation
- Explain the purpose and the process of lipogenesis
Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from carbohydrate precursors (Figure \(\PageIndex{1}\)). Lipid metabolism entails the oxidation of fatty acids to either generate energy or synthesize new lipids from smaller constituent molecules. Lipid metabolism is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids.
Lipid metabolism begins in the intestine where ingested triglycerides are broken down into smaller chain fatty acids and subsequently into monoglyceride molecules (see Figure \(\PageIndex{1}\) b ) by pancreatic lipases , enzymes that break down fats after they are emulsified by bile salts . When food reaches the small intestine in the form of chyme, a digestive hormone called cholecystokinin (CCK) is released by intestinal cells in the intestinal mucosa. CCK stimulates the release of pancreatic lipase from the pancreas and stimulates the contraction of the gallbladder to release stored bile salts into the intestine. CCK also travels to the brain, where it can act as a hunger suppressant.
Together, the pancreatic lipases and bile salts break down triglycerides into free fatty acids. These fatty acids can be transported across the intestinal membrane. However, once they cross the membrane, they are recombined to again form triglyceride molecules. Within the intestinal cells, these triglycerides are packaged along with cholesterol molecules in phospholipid vesicles called chylomicrons (Figure \(\PageIndex{2}\)). The chylomicrons enable fats and cholesterol to move within the aqueous environment of your lymphatic and circulatory systems. Chylomicrons leave the enterocytes by exocytosis and enter the lymphatic system via lacteals in the villi of the intestine. From the lymphatic system, the chylomicrons are transported to the circulatory system. Once in the circulation, they can either go to the liver or be stored in fat cells (adipocytes) that comprise adipose (fat) tissue found throughout the body.
Lipolysis
To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis , takes place in the cytoplasm. The resulting fatty acids are oxidized by β-oxidation into acetyl CoA, which is used by the Krebs cycle. The glycerol that is released from triglycerides after lipolysis directly enters the glycolysis pathway as DHAP. Because one triglyceride molecule yields three fatty acid molecules with as much as 16 or more carbons in each one, fat molecules yield more energy than carbohydrates and are an important source of energy for the human body. Triglycerides yield more than twice the energy per unit mass when compared to carbohydrates and proteins. Therefore, when glucose levels are low, triglycerides can be converted into acetyl CoA molecules and used to generate ATP through aerobic respiration.
The breakdown of fatty acids, called fatty acid oxidation or beta (β)-oxidation , begins in the cytoplasm, where fatty acids are converted into fatty acyl CoA molecules. This fatty acyl CoA combines with carnitine to create a fatty acyl carnitine molecule, which helps to transport the fatty acid across the mitochondrial membrane. Once inside the mitochondrial matrix, the fatty acyl carnitine molecule is converted back into fatty acyl CoA and then into acetyl CoA (Figure \(\PageIndex{3}\)). The newly formed acetyl CoA enters the Krebs cycle and is used to produce ATP in the same way as acetyl CoA derived from pyruvate.
Ketogenesis
If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies . These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starvation or when patients suffer from uncontrolled diabetes and cannot utilize most of the circulating glucose. In both cases, fat stores are liberated to generate energy through the Krebs cycle and will generate ketone bodies when too much acetyl CoA accumulates.
In this ketone synthesis reaction, excess acetyl CoA is converted into hydroxymethylglutaryl CoA (HMG CoA) . HMG CoA is a precursor of cholesterol and is an intermediate that is subsequently converted into β-hydroxybutyrate, the primary ketone body in the blood (Figure \(\PageIndex{4}\)).
Ketone Body Oxidation
Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO 2 and acetone. The acetone is removed by exhalation.  This effect provides one way of telling if a person with diabetes is properly controlling the disease. The carbon dioxide produced can acidify the blood, leading to diabetic ketoacidosis, a dangerous condition in people with diabetes.
Ketones oxidize to produce energy for the brain. beta (β)-hydroxybutyrate is oxidized to acetoacetate and NADH is released. An HS-CoA molecule is added to acetoacetate, forming acetoacetyl CoA. The carbon within the acetoacetyl CoA that is not bonded to the CoA then detaches, splitting the molecule in two. This carbon then attaches to another free HS-CoA, resulting in two acetyl CoA molecules. These two acetyl CoA molecules are then processed through the Krebs cycle to generate energy (Figure \(\PageIndex{5}\)).
Lipogenesis
When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis , creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocytes (liver cells). When you eat more glucose or carbohydrates than your body needs, your system uses acetyl CoA to turn the excess into fat. Although there are several metabolic sources of acetyl CoA, it is most commonly derived from glycolysis. Acetyl CoA availability is significant, because it initiates lipogenesis. Lipogenesis begins with acetyl CoA and advances by the subsequent addition of two carbon atoms from another acetyl CoA; this process is repeated until fatty acids are the appropriate length. Because this is a bond-creating anabolic process, ATP is consumed. However, the creation of triglycerides and lipids is an efficient way of storing the energy available in carbohydrates. Triglycerides and lipids, high-energy molecules, are stored in adipose tissue until they are needed.
Although lipogenesis occurs in the cytoplasm, the necessary acetyl CoA is created in the mitochondria and cannot be transported across the mitochondrial membrane. To solve this problem, pyruvate is converted into both oxaloacetate and acetyl CoA. Two different enzymes are required for these conversions. Oxaloacetate forms via the action of pyruvate carboxylase, whereas the action of pyruvate dehydrogenase creates acetyl CoA. Oxaloacetate and acetyl CoA combine to form citrate, which can cross the mitochondrial membrane and enter the cytoplasm. In the cytoplasm, citrate is converted back into oxaloacetate and acetyl CoA. Oxaloacetate is converted into malate and then into pyruvate. Pyruvate crosses back across the mitochondrial membrane to wait for the next cycle of lipogenesis. The acetyl CoA is converted into malonyl CoA that is used to synthesize fatty acids. Figure \(\PageIndex{6}\) summarizes the pathways of lipid metabolism.


27: Site-specific recombination
Summary
Both the Cre-lox and FLP-FRT systems are used for site-specific recombination to facilitate genome editing, especially for achieving tissue or temporal specificity.
Also known as
Variants: Cre-lox, FLP-FRT
Samples needed
Cells or organisms to be modified
Method
Site-specific combination requires two elements: A recombinase enzyme that catalyzes DNA cleavage and re-ligation, and two recombination sites in the DNA. The two most commonly used recombinase-recombination site pairs are Cre-lox and FLP-FRT. The recombination sites are made up of an asymmetrical core region where the cuts occur, flanked by inverted repeats where the recombinase binds the DNA. For recombination to occur between two recombination sites, the core sequences must be identical and they must be aligned in the same direction in space, which can require looping of the DNA. The directionality of the recombination sites is determined by the asymmetrical core sequence.
If the two recombination sites are aligned in the same direction in a piece of DNA, when recombination occurs, the intervening sequence will be removed. If the two sites are pointing toward one another, the intervening sequence will be inverted.
Site-specific recombination is often used in animal models. One of the benefits of site-specific recombination is that the genomic modification can be confined to a specific tissue by using a recombinase (Cre or FLP) under the control of a tissue-specific promoter. Alternatively, temporal specificity can be achieved through the use of inducible recombinases, like the Cre-ER fusion protein. Cre-ER only translocates to the nucleus, and therefore can only catalyze site-specific recombination, in the presence of either tamoxifen or 4-OHT, which can be supplied orally or injected. So, in this case, the researchers control the point at which the site-specific recombination occurs.
Controls
Unmodified control
Interpretation
In this experiment, researchers set out to identify all cells descended from cells expressing WOX5 , which is known to be expressed in the root primordia & root stem cell niche. To do this, they used an inducible Cre-lox system. As shown in “Construct 2” in panel B, this system used two reporters. Before recombination, GFP is expressed, and after recombination, GUS is expressed. GFP is fluorescent, and GUS is an enzyme that can cleave a chemical to produce a blue precipitate. This construct is under the control of the 35S ribosomal RNA promoter, which is active in all cells.
In this system, the researchers used a Cre fusion protein, Cre-GR (glucocorticoid receptor). This protein is usually found in the cytosol and will only enter the nucleus in the presence of the chemical dexamethasone (dex). Therefore, in order for site-specific recombination to occur, the Cre-GR protein must be expressed (only occurs in tissues where the WOX5 promoter is active) and dexamethasone must be provided by the researcher. Thus, the system provides both tissue specificity ( WOX5 promoter) and temporal specificity (dex administration). Once recombination occurs, the cell’s genome is permanently modified, and any descendents of that cell will also express GUS instead of GFP. In this way, one can identify all the descendants of particular cells. This kind of lineage tracing analysis is often used to identify all the descendants of particular stem cells.
In this experiment, the Zhai and Xu wanted to determine if the “adventitious” root cells, i.e. root cells that form from non-root tissue, like explanted leaves, are descendants of WOX5 -expressing cells. In panels E and F, we can see that the adventitious root (AR) cells and adventitious root primordium (ARP) both express GUS in the presence of dex, indicating that they do indeed descend from WOX5 -expressing cells. If their parent cell did not express WOX5 , they would not express Cre-GR, recombination would not have occurred, and the descendents would all express GFP instead of GUS.
Image Descriptions
Figure 1 image description:
A: Photo of a leaf with an adventitious root (AR) growing from it.
B: Schematic of Cre-lox system. Construct 1: WOX5 pro - Cre-GR - ter. Transcription leads to Cre-GR protein. Construct 2: S35 pro - LOX - GFP - ter - LOX - GUS - ter. Cre-GR + dex leads to recombination to: S35 pro - GUS - ter , which leads to GUS signal.
C: Photo of seedling showing green fluorescence.
D: Photo of root showing green fluorescence.
E: Photo of two explanted leaves with ARs growing from them. Left, +dex, shows dark blue staining throughout AR, whereas right, -dex, shows no staining.
F: Photo zooming in on bottom of explanted leaf. There is a spot of GUS staining near the bottom of the leaf labeled ARP for adventitious root primordium.
Thumbnail
"Cre-lox inversion.svg" ↗ by Staticd is licensed under CC BY-SA 3.0 ↗.
Description: Inversion of a DNA sequence between two inverted Lox sites.
Author
Katherine Mattaini, Tufts University
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Zhai, N., and L. Xu. 2020. CRE/LOX-based analysis of cell lineage during root formation and regeneration in Arabidopsis. aBIOTECH 1:153–156. ↵


5.1: Infinity, limits, and power functions
- How can we use limit notation to succinctly express a function's behavior as the input increases without bound or as the function's value increases without bound?
- What are some important limits and trends involving \(\infty\) that we can observe for familiar functions such as \(e^x\text{,}\) \(\ln(x)\text{,}\) \(x^2\text{,}\) and \(\frac{1}{x}\text{?}\)
- What is a power function and how does the value of the power determine the function's overall behavior?
In Section 3.2 , we compared the behavior of the exponential functions \(p(t) = 2^t\) and \(q(t) = (\frac{1}{2})^t\text{,}\) and observed in Figure 3.2.5 that as \(t\) increases without bound, \(p(t)\) also increases without bound, while \(q(t)\) approaches \(0\) (while having its value be always positive). We also introduced shorthand notation for describing these phenomena, writing
and
It's important to remember that infinity is not itself a number. We use the “\(\infty\)” symbol to represent a quantity that gets larger and larger with no bound on its growth.
We also know that the concept of infinity plays a key role in understanding the graphical behavior of functions. For instance, we've seen that for a function such as \(F(t) = 72 - 45e^{-0.05t}\text{,}\) \(F(t) \to 72\) as \(t \to \infty\text{,}\) since \(e^{-0.05t} \to 0\) as \(t\) increases without bound. The function \(F\) can be viewed as modeling the temperature of an object that is initially \(F(0) = 72-45 = 27\) degrees that eventually warms to \(72\) degrees. The line \(y = 72\) is thus a horizontal asymptote of the function \(F\text{.}\)
In Preview \(\PageIndex{1}\) , we review some familiar functions and portions of their behavior that involve \(\infty\text{.}\)
Complete each of the following statements with an appropriate number or the symbols \(\infty\) or \(-\infty\text{.}\) Do your best to do so without using a graphing utility; instead use your understanding of the function's graph.
- As \(t \to \infty\text{,}\) \(e^{-t} \to \).
- As \(t \to \infty\text{,}\) \(\ln(t) \to \).
- As \(t \to \infty\text{,}\) \(e^{t} \to \).
- As \(t \to 0^+\text{,}\) \(e^{-t} \to \). (When we write \(t \to 0^+\text{,}\) this means that we are letting \(t\) get closer and closer to \(0\text{,}\) but only allowing \(t\) to take on positive values.)
- As \(t \to \infty\text{,}\) \(35 + 53e^{-0.025t} \to\).
- As \(t \to \frac{\pi}{2}^-\text{,}\) \(\tan(t) \to \). (When we write \(t \to \frac{\pi}{2}^-\text{,}\) this means that we are letting \(t\) get closer and closer to \(\frac{\pi}{2}^-\text{,}\) but only allowing \(t\) to take on values that lie to the left of \(\frac{\pi}{2}\text{.}\))
- As \(t \to \frac{\pi}{2}^+\text{,}\) \(\tan(t) \to \). (When we write \(t \to \frac{\pi}{2}^+\text{,}\) this means that we are letting \(t\) get closer and closer to \(\frac{\pi}{2}^+\text{,}\) but only allowing \(t\) to take on values that lie to the right of \(\frac{\pi}{2}\text{.}\))
Limit notation
When observing a pattern in the values of a function that correspond to letting the inputs get closer and closer to a fixed value or letting the inputs increase or decrease without bound, we are often interested in the behavior of the function “in the limit”. In either case, we are considering an infinite collection of inputs that are themselves following a pattern, and we ask the question “how can we expect the function's output to behave if we continue?”
For instance, we have regularly observed that “as \(t \to \infty\text{,}\) \(e^{-t} \to 0\text{,}\)” which means that by allowing \(t\) to get bigger and bigger without bound, we can make \(e^{-t}\) get as close to \(0\) as we'd like (without \(e^{-t}\) ever equalling \(0\text{,}\) since \(e^{-t}\) is always positive).
Similarly, as seen in Figure \(\PageIndex{1}\) and Figure \(\PageIndex{2}\) , we can make such observations as \(e^t \to \ infty \) as \(t \to \ infty \text{,}\) \(\ln(t) \to \ infty \) as \(t \to \ infty \text{,}\) and \(\ln(t) \to -\ infty \) as \(t \to 0^+\text{.}\) We introduce formal limit notation in order to be able to express these patterns even more succinctly.
Let \(L\) be a real number and \(f\) be a function. If we can make the value of \(f(t)\) as close to \(L\) as we want by letting \(t\) increase without bound, we write
and say that the limit of \(f\) as \(t\) increases without bound is \(L\) .
If the value of \(f(t)\) increases without bound as \(t\) increases without bound, we instead write
Finally, if \(f\) doesn't increase without bound, doesn't decrease without bound, and doesn't approach a single value \(L\) as \(t \to \infty\text{,}\) we say that \(f\) does not have a limit as \(t \to \infty\) .
We use limit notation in related, natural ways to express patterns we see in function behavior. For instance, we write \(t \to -\infty\) when we let \(t\) decrease without bound, and \(f(t) \to -\infty\) if \(f\) decreases without bound. We can also think about an input value \(t\) approaching a value \(a\) at which the function \(f\) is not defined. As one example, we write
because the natural logarithm function decreases without bound as input values get closer and close to \(0\) (while always being positive), as seen in Figure 5.1.2.
In the situation where \(\lim_{t \to \infty} f(t) = L\text{,}\) this tells us that \(f\) has a horizontal asymptote at \(y = L\) since the function's value approaches this fixed number as \(t\) increases without bound. Similarly, if we can say that \(\lim_{t \to a} f(t) = \infty\text{,}\) this shows that \(f\) has a vertical asymptote at \(x = a\) since the function's value increases without bound as inputs approach the fixed number \(a\text{.}\)
For now, we are going to focus on the long-range behavior of certain basic, familiar functions and work to understand how they behave as the input increases or decreases without bound. Above we've used the input variable \(t\) in most of our previous work; going forward, we'll regularly use \(x\) as well.
Complete the Table 5.1.4 by entering “\(\infty\text{,}\)” “\(-\infty\text{,}\)” “\(0\text{,}\)” or “no limit” to identify how the function behaves as either \(x\) increases or decreases without bound. As much as possible, work to decide the behavior without using a graphing utility.
| \(f(x)\) | \(\lim_{x \to \infty} f(x)\) | \(\lim_{x \to -\infty} f(x)\) |
| \(e^x\) | ||
| \(e^{-x}\) | ||
| \(\ln(x)\) | ||
| \(x\) | ||
| \(x^2\) | ||
| \(x^3\) | ||
| \(x^4\) | ||
| \(\frac{1}{x}\) | ||
| \(\frac{1}{x^2}\) | ||
| \(\sin(x)\) |
Power functions
To date, we have worked with several families of functions: linear functions of form \(y = mx + b\text{,}\) quadratic functions in standard form, \(y = ax^2 + bx + c\text{,}\) the sinusoidal (trigonometric) functions \(y = a\sin(k(x-b))+c\) or \(y = a\cos(k(x-b))+c\text{,}\) transformed exponential functions such as \(y = ae^{kx} + c\text{,}\) and transformed logarithmic functions of form \(y = a\ln(x) + c\text{.}\) For trigonometric, exponential, and logarithmic functions, it was essential that we first understood the behavior of the basic parent functions \(\sin(x)\text{,}\) \(\cos(x)\text{,}\) \(e^x\text{,}\) and \(\ln(x)\text{.}\) In order to build on our prior work with linear and quadratic functions, we now consider basic functions such as \(x\text{,}\) \(x^2\text{,}\) and additional powers of \(x\text{.}\)
A function of the form \(f(x) = x^p\) where \(p\) is any real number is called a power function .
We first focus on the case where \(p\) is a natural number (that is, a positive whole number).
Point your browser to the Desmos worksheet at http://gvsu.edu/s/0zu . In what follows, we explore the behavior of power functions of the form \(y = x^n\) where \(n \ge 1\text{.}\)
- Press the “play” button next to the slider labeled “\(n\text{.}\)” Watch at least two loops of the animation and then discuss the trends that you observe. Write a careful sentence each for at least two different trends.
- Click the icons next to each of the following 8 functions so that you can see all of \(y = x\text{,}\) \(y = x^2\text{,}\) \(\ldots\text{,}\) \(y = x^8\) graphed at once. On the interval \(0 \lt x \lt 1\text{,}\) how do the graphs of \(x^a\) and \(x^b\) compare if \(a \lt b\text{?}\)
- Uncheck the icons on each of the 8 functions to hide their graphs. Click the settings icon to change the domain settings for the axes, and change them to \(-10 \le x \le 10\) and \(-10,000 \le y \le 10,000\text{.}\) Play the animation through twice and then discuss the trends that you observe. Write a careful sentence each for at least two different trends.
- Click the icons next to each of the following 8 functions so that you can see all of \(y = x\text{,}\) \(y = x^2\text{,}\) \(\ldots\text{,}\) \(y = x^8\) graphed at once. On the interval \(x \gt 1\text{,}\) how do the graphs of \(x^a\) and \(x^b\) compare if \(a \lt b\text{?}\)
In the situation where the power \(p\) is a negative integer (i.e., a negative whole number), power functions behave very differently. This is because of the property of exponents that states
so for a power function such as \(p(x) = x^{-2}\text{,}\) we can equivalently consider \(p(x) = \frac{1}{x^2}\text{.}\) Note well that for these functions, their domain is the set of all real numbers except \(x = 0\text{.}\) Like with power functions with positive whole number powers, we want to know how power functions with negative whole number powers behave as \(x\) increases without bound, as well as how the functions behave near \(x = 0\text{.}\)
Point your browser to the Desmos worksheet at http://gvsu.edu/s/0zv . In what follows, we explore the behavior of power functions \(y = x^n\) where \(n \le -1\text{.}\)
- Press the “play” button next to the slider labeled “\(n\text{.}\)” Watch two loops of the animation and then discuss the trends that you observe. Write a careful sentence each for at least two different trends.
- Click the icons next to each of the following 8 functions so that you can see all of \(y = x^{-1}\text{,}\) \(y = x^{-2}\text{,}\) \(\ldots\text{,}\) \(y = x^{-8}\) graphed at once. On the interval \(1 \lt x\text{,}\) how do the functions \(x^a\) and \(x^b\) compare if \(a \lt b\text{?}\) (Be careful with negative numbers here: e.g., \(-3 \lt -2\text{.}\))
- How do your answers change on the interval \(0 \lt x \lt 1\text{?}\)
- Uncheck the icons on each of the 8 functions to hide their graphs. Click the settings icon to change the domain settings for the axes, and change them to \(-10 \le x \le 10\) and \(-10,000 \le y \le 10,000\text{.}\) Play the animation through twice and then discuss the trends that you observe. Write a careful sentence each for at least two different trends.
- Explain why \(\lim_{x \to \infty} \frac{1}{x^n} = 0\) for any choice of \(n = 1, 2, \ldots\text{.}\)
Summary
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The notation
\[ \lim_{x \to \infty} f(x) = L \nonumber \]
means that we can make the value of \(f(x)\) as close to \(L\) as we'd like by letting \(x\) be sufficiently large. This indicates that the value of \(f\) eventually stops changing much and tends to a single value, and thus \(y = L\) is a horizontal asymptote of the function \(f\text{.}\)
Similarly, the notation
\[ \lim_{x \to a} f(x) = \infty \nonumber \]means that we can make the value of \(f(x)\) as large as we'd like by letting \(x\) be sufficiently close, but not equal, to \(a\text{.}\) This unbounded behavior of \(f\) near a finite value \(a\) indicates that \(f\) has a vertical asymptote at \(x = a\text{.}\)
- We summarize some key behavior of familiar basic functions with limits as \(x\) increases without bound in Table 5.1.6.
| \(f(x)\) | \(\lim_{x \to \infty} f(x)\) | \(\lim_{x \to -\infty} f(x)\) |
| \(e^x\) | \(\infty\) | \(0\) |
| \(e^{-x}\) | \(0\) | \(\infty\) |
| \(\ln(x)\) | \(\infty\) | NA 1 |
| \(x\) | \(\infty\) | \(-\infty\) |
| \(x^2\) | \(\infty\) | \(\infty\) |
| \(x^3\) | \(\infty\) | \(-\infty\) |
| \(x^4\) | \(\infty\) | \(\infty\) |
| \(\frac{1}{x}\) | \(0\) | \(0\) |
| \(\frac{1}{x^2}\) | \(0\) | \(0\) |
| \(\sin(x)\) | no limit 2 |
no limit
|
Additionally, Table 5.1.7 summarizes some key familiar function behavior where the function's output increases or decreases without bound as \(x\) approaches a fixed number not in the function's domain.
| \(f(x)\) | \(\lim_{x \to a^-} f(x)\) |
\(\lim_{x \to a^+} f(x)\)
|
| \(\ln(x)\) | NA | \(\lim_{x \to 0^+} \ln(x) = -\infty\) |
| \(\frac{1}{x}\) | \(\lim_{x \to 0^-} \frac{1}{x} = -\infty\) | \(\lim_{x \to 0^+} \frac{1}{x} = \infty\) |
| \(\frac{1}{x^2}\) | \(\lim_{x \to 0^-} \frac{1}{x^2} = \infty\) |
\(\lim_{x \to 0^+} \frac{1}{x^2} = \infty\)
|
| \(\tan(x)\) | \(\lim_{x \to \frac{\pi}{2}^-} \tan(x) = \infty\) | \(\lim_{x \to \frac{\pi}{2}^+} \tan(x) = -\infty\) |
| \(\sec(x)\) | \(\lim_{x \to \frac{\pi}{2}^-} \sec(x) = \infty\) | \(\lim_{x \to \frac{\pi}{2}^+} \sec(x) = -\infty\) |
| \(\csc(x)\) | \(\lim_{x \to 0^-} \sec(x) = -\infty\) | \(\lim_{x \to 0^+} \sec(x) = \infty\) |
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A power function is a function of the form \(f(x) = x^p\) where \(p\) is any real number. For the two cases where \(p\) is a positive whole number or a negative whole number, it is straightforward to summarize key trends in power functions' behavior.
- If \(p = 1, 2, 3, \ldots\text{,}\) then the domain of \(f(x) = x^p\) is the set of all real numbers, and as \(x \to \infty\text{,}\) \(f(x) \to \infty\text{.}\) For the limit as \(x \to -\infty\text{,}\) it matters whether \(p\) is even or odd: if \(p\) is even, \(f(x) \to \infty\) as \(x \to -\infty\text{;}\) if \(p\) is odd, \(f(x) \to -\infty\) as \(x \to \infty\text{.}\) Informally, all power functions of form \(f(x) = x^p\) where \(p\) is a positive even number are “U-shaped”, while all power functions of form \(f(x) = x^p\) where \(p\) is a positive odd number are “chair-shaped”.
- If \(p = -1, -2, -3, \ldots\text{,}\) then the domain of \(f(x) = x^p\) is the set of all real numbers except \(x=0\text{,}\) and as \(x \to \pm \infty\text{,}\) \(f(x) \to 0\text{.}\) This means that each such power function with a negative whole number exponent has a horizontal asymptote of \(y = 0\text{.}\) Regardless of the value of \(p\) (\(p = -1, -2, -3, \ldots\)), \(\lim_{x \to 0^+} f(x) = \infty\text{.}\) But when we approach \(0\) from the negative side, it matters whether \(p\) is even or odd: if \(p\) is even, \(f(x) \to \infty\) as \(x \to 0^-\text{;}\) if \(p\) is odd, \(f(x) \to -\infty\) as \(x \to 0^-\text{.}\) Informally, all power functions of form \(f(x) = x^p\) where \(p\) is a negative odd number look similar to \(\frac{1}{x}\text{,}\) while all power functions of form \(f(x) = x^p\) where \(p\) is a negative even number look similar to \(\frac{1}{x^2}\text{.}\)
Exercises 5.1.4 Exercises
We've observed that several different familiar functions grow without bound as \(x \to \infty\text{,}\) including \(f(x) = \ln(x)\text{,}\) \(g(x) = x^2\text{,}\) and \(h(x) = e^x\text{.}\) In this exercise, we compare and contrast how these three functions grow.
- Use a computational device to compute decimal expressions for \(f(10)\text{,}\) \(g(10)\text{,}\) and \(h(10)\text{,}\) as well as \(f(100)\text{,}\) \(g(100)\text{,}\) and \(h(100)\text{.}\) What do you observe?
- For each of \(f\text{,}\) \(g\text{,}\) and \(h\text{,}\) how large an input is needed in order to ensure that the function's output value is at least \(10^{10}\text{?}\) What do these values tell us about how each function grows?
- Consider the new function \(r(x) = \frac{g(x)}{h(x)} = \frac{x^2}{e^x}\text{.}\) Compute \(r(10)\text{,}\) \(r(100)\text{,}\) and \(r(1000)\text{.}\) What do the results suggest about the long-range behavior of \(r\text{?}\) What is surprising about this, in light of the fact that both \(x^2\) and \(e^x\) grow without bound?
Consider the familiar graph of \(f(x) = \frac{1}{x}\text{,}\) which has a vertical asypmtote at \(x = 0\) and a horizontal asymptote at \(y = 0\text{,}\) as pictured in Figure \(\PageIndex{8}\) In addition, consider the similarly-shaped function \(g\) shown in Figure \(\PageIndex{9}\) , which has vertical asymptote \(x = -1\) and horizontal asymptote \(y = -2\text{.}\)
- How can we view \(g\) as a transformation of \(f\text{?}\) Explain, and state how \(g\) can be expressed algebraically in terms of \(f\text{.}\)
- Find a formula for \(g\) as a function of \(x\text{.}\) What is the domain of \(g\text{?}\)
- Explain algebraically (using the form of \(g\) from (b)) why \(\lim_{x \to \infty} g(x) = -2\) and \(\lim_{x \to -1^+} g(x) = \infty\text{.}\)
- What if a function \(h\) (again of a similar shape as \(f\)) has vertical asymptote \(x = 5\) and horizontal asymtote \(y = 10\text{.}\) What is a possible formula for \(h(x)\text{?}\)
- Suppose that \(r(x) = \frac{1}{x+35} - 27\text{.}\) Without using a graphing utility, how do you expect the graph of \(r\) to appear? Does it have a horizontal asymptote? A vertical asymptote? What is its domain?
Power functions can have powers that are not whole numbers. For instance, we can consider such functions as \(f(x)=x^{2.4}\text{,}\) \(g(x)=x^{2.5}\text{,}\) and \(h(x)=x^{2.6}\text{.}\)
- Compare and contrast the graphs of \(f\text{,}\) \(g\text{,}\) and \(h\text{.}\) How are they similar? How are they different? (There is a lot you can discuss here.)
- Observe that we can think of \(f(x) = x^{2.4}\) as \(f(x) = x^{24/10} = x^{12/5}\text{.}\) In addition, recall by exponent rules that we can also view \(f\) as having the form \(f(x) = \sqrt[5]{x^{12}}\text{.}\) Write \(g\) and \(h\) in similar forms, and explain why \(g\) has a different domain than \(f\) and \(h\text{.}\)
- How do the graphs of \(f\text{,}\) \(g\text{,}\) and \(h\) compare to the graphs of \(y = x^2\) and \(y = x^3\text{?}\) Why are these natural functions to use for comparison?
- Explore similar questions for the graphs of \(p(x) = x^{-2.4}\text{,}\) \(q(x) = x^{-2.5}\text{,}\) and \(r(x) = x^{-2.6}\text{.}\)


1.2.7: Mental Health - Risks, Causes, and Treatments
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Mental illnesses, in general, are thought to be caused by a variety of genetic and environmental factors, these include:
- Inherited traits. Mental illness is more common in people whose blood relatives also have a mental illness. Certain genes may increase your risk of developing a mental illness, and your life situation may trigger it.
- Environmental exposures before birth. Exposure to environmental stressors, inflammatory conditions, toxins, alcohol or drugs while in the womb can sometimes be linked to mental illness.
- Brain chemistry.  When the neural networks involving these chemicals are impaired, the function of nerve receptors and nerve systems change, leading to depression and other emotional disorders.
Certain factors may increase your risk of developing a mental illness, including:
- A history of mental illness in a blood relative, such as a parent or sibling
- Stressful life situations, such as financial problems, a loved one’s death or a divorce
- An ongoing (chronic) medical condition, such as diabetes
- Brain damage as a result of a serious injury (traumatic brain injury), such as a violent blow to the head
- Traumatic experiences, such as military combat or assault
- Use of alcohol or recreational drugs
- A childhood history of abuse or neglect
- Few friends or few healthy relationships
- A previous mental illness
Treatment begins with getting a medical diagnosis to understand which mental illness may be causing your symptoms. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association, is used for diagnosis. Treatment depends on the type of mental disorder and may include medications, physicians, psychotherapist, psychiatrists, and social workers or family members.
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Psychotherapy
- Psychotherapy or “talk therapy” can help people with anxiety disorders. To be effective, psychotherapy must be directed at the person’s specific anxieties and tailored to his or her needs. A typical “side effect” of psychotherapy is temporary discomfort involved with thinking about confronting feared situations.
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Cognitive Behavioral Therapy (CBT)
- CBT is a type of psychotherapy that can help people with anxiety disorders. It teaches a person different ways of thinking, behaving, and reacting to anxiety-producing and fearful situations. CBT can also help people learn and practice social skills, which is vital for treating social anxiety disorder.
- Two specific stand-alone components of CBT used to treat social anxiety disorder are cognitive therapy and exposure therapy. Cognitive therapy focuses on identifying, challenging, and then neutralizing unhelpful thoughts underlying anxiety disorders. Exposure therapy focuses on confronting the fears underlying an anxiety disorder in order to help people engage in activities they have been avoiding.
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Stress-Management Techniques
- Stress management techniques and meditation can help people with anxiety disorders calm themselves and may enhance the effects of therapy. While there is evidence that aerobic exercise has a calming effect, the quality of the studies is not strong enough to support its use as treatment. Since caffeine, certain illicit drugs, and even some over-the-counter cold medications can aggravate the symptoms of anxiety disorders, avoiding them should be considered. Check with your physician or pharmacist before taking any additional medications.
- The family can be important in the recovery of a person with an anxiety disorder. Ideally, the family should be supportive but not help perpetuate their loved one’s symptoms. Talking with a trusted friend or member of the clergy can also provide support, but it is not necessarily a sufficient alternative to care from an expert clinician.
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Medication
- Medication does not cure anxiety disorders but often relieves symptoms. Medication can only be prescribed by a medical doctor (such as a psychiatrist or a primary care provider), but a few states allow psychologists to prescribe psychiatric medications.
- Medications are sometimes used as the initial treatment of an anxiety disorder, or are used only if there is insufficient response to a course of psychotherapy. In research studies, it is common for patients treated with a combination of psychotherapy and medication to have better outcomes than those treated with only one or the other.
- The most common classes of medications used to combat anxiety disorders are antidepressants, anti-anxiety drugs, and beta-blockers. Be aware that some medications are effective only if they are taken regularly and that symptoms may recur if the medication is stopped.


4.6: Summary
An asset costs $27,000, has a residual value of $900, and has a three-year or 8,700-hour useful life. The company used the asset as follows: 2,200 hours in 2012; 2,500 hours in 2013; 2,700 hours in 2014; and 2,400 hours in 2015.
| Method | Process | Comments | Example (below) | |||||||||||||||||||||||||
| Straight-Line |
\(\ \frac{\text{
Cost - Residual value }}{\text{Useful life in years }}\) |
Asset is fully depreciated once it has been used the number of years in its useful life. | \(\ \frac{27,000 - 900}{3}\) | = 8,700 per year | ||||||||||||||||||||||||
| Units of Production |
\(\ \frac{\text{
Cost - Residual value }}{\text{Useful life in hours }}\) |
Multiply hourly rate times number of hours used in the year. Asset is fully depreciated once it has been used the number of hours in its useful life. | \(\ \frac{27,000 - 600}{8,700}\) | = $3 per hour | ||||||||||||||||||||||||
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2,100 in year 1 ($3 x 2200 hours) 2,300 in year 2 ($3 x 2500 hours) 2,600 in year 3 ($3 x 2700 hours) 1,700 in year 4 ($3 x 2400 hours) |
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| Declining Balance (“Twice the straight-line rate” just means to divide 2 by the number of years) | Multiply the book value at the beginning of each year by 2/ number of years to determine the amount for the adjusting entry. |
Do not subtract out residual value at the beginning (which you did for straight-line.)
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6.3: Material Practices of Writing
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My primary purpose in this chapter is to assess the function and meaning of writing in the prehistoric Aegean by focusing on the material practices of writing. During the Middle and Late Bronze Ages ( c. 2000–1200 bc) an uncertain number of scripts was in use on Crete. In the pre-Mycenaean period, the two most important are known as Linear A and Minoan or Cretan Hieroglyphic ( Figures 1–2 ; see also Flouda, this volume). Although the two writing systems do not seem to have been used for exactly the same purposes, as they occur on different types of documents, they were both associated with the palatial administration. Linear A is in its earliest form found at the Palace at Phaistos in south-central Crete, while Minoan Hieroglyphic was associated with the palaces at Knossos, Malia, and Petras in the north and northeast (see also Flouda, Finalyson and Tomas, all this volume). Both scripts are syllabic. After the destruction of the first palaces ( c. 1700 bc), Cretan Hieroglyphic seems to go out of use and is replaced by Linear A for reasons that are still unclear (cf. Finalyson, this volume).
As the two forms of writing can be geographically differentiated in the early palatial period, it is a plausible assumption that they represent different languages, but in view of the fact that neither script has been deciphered this cannot be verified (cf. Olivier 1986: 387; Schoep 1999: 265; 2007; see Younger and Rehak 2008: 176 for the view that there was only one Cretan language). It has, however, been suggested that Linear A and Cretan Hieroglyphic have a common origin in an earlier prepalatial script, known as the ‘Archanes script’ ( Figure 3 ). This early form of writing takes its name after Archanes in central Crete, where a number of seals inscribed with this script were found in burials (Schoep 1999: 266–267; 2006: 45–46, n. 73). If it is the case that both Linear A and Cretan Hieroglyphic have the same origin, the later development of two different
forms of writing associated with the palatial administration in different parts of the island is perhaps to be seen in terms of the deliberate construction of separate regional identities, in which language may or may not have been a factor.
In the Late Bronze Age a new script known as Linear B was invented and became the only script in use on both Crete and the Greek mainland ( Figure 4a–b ; see Tomas, this volume). Linear B was developed from Linear A in order to write Greek and was closely associated with the Mycenaean palace administration. In contrast to Linear A and Cretan Hieroglyphic, Linear B has been deciphered and the documents on which it occurs can be read with a high degree of certainty. Exactly when Linear B was invented is an open question, but it may have been much earlier than the date of the first documents that have been preserved. Whether Linear B was first used on Crete or on the Mainland is also an open question.
A thin clay disc known as the Phaistos Disc represents another possible but controversial example of writing. It was found with a fragment of a Linear A tablet and dates to the Middle Bronze Age. A number of signs, some of them repeated, are arranged in a spiral on both sides of the disc. A few are vaguely comparable to signs of the Cretan hieroglyphic script, but on the whole they bear no conclusive resemblance to either Linear A or Cretan Hieroglyphic. If the signs constitute writing it is in an otherwise unattested form. As a writing support the disc is also unique in its circular shape and in contrast to the clay tablets used in the palatial administrative systems it had been deliberately baked. Strictly speaking, a form of writing that is attested solely on a single artefact should not be really classified as an example of a functional writing system. I have else- where suggested that the inscription on the Phaistos Disc could be an example of pseudo-writing (Whittaker 2005; cf. Flouda, this volume).
In the Aegean writing occurs on a number of different types of material supports, made of clay, bone, stone or metal. The use of these varies with time and place. The range of materials used as supports is much more extensive for Crete than for the Greek mainland. Clay tablets represent the largest group of preserved texts. Their use was associated with the palatial administration on both Crete and the mainland and spans the Middle and Late Bronze Ages. Their first occurrence is associated with the establishment of the Minoan palace system c. 2000 bc. The latest tablets date to the destruction of the Mycenaean palaces c. 1200 bc. Clay was a material that was readily available, as good sources are found on both Crete and the Greek mainland. Clay tablets are objects that have been fashioned solely for the purpose of being written on, and their shape and size would have been determined by the specifics of this use, by the system of storage, or by the needs of the scribes. They were used for all three of the major scripts, and the shape of the tablet correlates with the type of writing found on them. Cretan Hieroglyphic is generally found on two-sided or four-sided bars, while Linear A and Linear B are found on page-shaped tablets; the ones used for Linear A are generally smaller than the ones used for Linear B. Linear B is also found on tablets which are much wider than they are long (often called leaf-shaped or palm leaf-shaped). The tablets sometimes have writing on more than one side; the four-sided bars are generally inscribed on all sides. All types of tablets were made in the same way. After being fashioned from the wet clay, they were air-dried until they had hardened to the consistency of leather and were ready to be written on. Some kind of stylus with a sharp point was used for writing. It has been claimed that the function of several thin rods made of bone and in one case of bronze found at Tiryns was for writing Linear B (Cultraro 2006: 24). Otherwise, styli have not been recognised in the archaeological record, which may be an indication that they were commonly made of wood and thus less likely to survive. This is perhaps indicated by the fact that some inscriptions include the impressions of a stylus that had been roughly made and in some cases had a split end (Hallager 1996: 29). Chadwick (1976: 18) suggests that a thorn fastened to some kind of holder could have been used for the very fine writing found on some tablets.
When a scribe had finished recording information on a tablet it was left to dry completely before being placed in a basket or a wooden container and archived. It was possible to reuse a tablet which had already been inscribed and dried by moistening it so that the surface could be flattened and whatever had been written on it erased. When it had dried sufficiently, the tablet could then be re-inscribed. Many Linear A tablets are in fact palimpsests, indicating that the palace bureaucracies had some kind of recycling scheme in place (Schoep 2002: 79). The use of clay tablets can be seen as providing material weight and durability to the information recorded on them. It is, however, possible that for certain types of texts in the palace bureaucracies, clay may have been chosen as a support because its material properties afforded impermanency as much as permanency (see also Piquette, this volume). In light of evidence for re-use, the information recorded on clay tablets, in all or most cases, may have been of an ephemeral nature. Nevertheless, since all Aegean tablets were unbaked, their survival as archaeological artefacts was dependent on them being exposed to fire in some other way. The majority that have been preserved as legible documents have been found in the destruction layers of the palaces, which they do not in most cases antedate by long periods of time.
Other types of clay objects that may carry script are the so-called roundels, various types of sealings, and ceramic vessels used for storage or transport. Roundels are thick clay disks with seal impressions, which have usually been inscribed with signs in Linear A on one or both faces (see also Finalyson, this volume). Their function is uncertain, but almost all have been found in archival contexts; one suggestion is that they were receipts given in return for the delivery of goods from the palaces (Hallager 1996: 116–120). Their use is restricted to the period of the new palaces on Crete ( c. 1700 – c. 1450 bc). All three scripts can occur on sealings. However, while a stylus was always used to write Linear A and B on all types of clay documents, Cretan Hieroglyphic could also be written with seals, which were pressed into the clay in order to produce a meaningful text. Like the tablets, roundels and sealings have only been preserved if they have been accidently burnt. All three scripts can also be found either inscribed or painted on different types of ceramic vases. Texts in Linear B were normally painted on the pots before they were fired. Inscriptions on pots were meaningful in the sense that they were intended to provide information about place or time of fabrication, ownership or function. Potsherds, often referred to with the Greek word ostraka , were commonly used for informal writing in the historical Greek period (Thomas 1992: 57, 83 compares them to our scrap paper). This does not seem to have been the case in the Bronze Age. As far as I know, the only example from the prehistoric Aegean is an ostrakon from Akrotiri on Thera in the Cyclades, which has some kind of calculation in Linear A scratched on it (Michailidou 1992–1993).


17: The Endocrine System
In order to survive, animals must constantly adapt to changes in the environment. The nervous and endocrine systems both work together to bring about this adaptation. In general the nervous system responds rapidly to short-term changes by sending electrical impulses along nerves and the endocrine system brings about longer-term adaptations by sending out chemical messengers called hormones into the blood stream.
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- 17.0: Prelude to the Endocrine System
- You may never have thought of it this way, but when you send a text message to two friends to meet you at the dining hall at six, you’re sending digital signals that (you hope) will affect their behavior—even though they are some distance away. Similarly, certain cells send chemical signals to other cells in the body that influence their behavior. This long-distance intercellular communication, coordination, and control is critical for homeostasis, and it is the function of the endocrine system.
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- 17.1: An Overview of the Endocrine System
- Communication is a process in which a sender transmits signals to one or more receivers to control and coordinate actions. In the human body, two major organ systems participate in relatively “long distance” communication: the nervous system and the endocrine system. Together, these two systems are primarily responsible for maintaining homeostasis in the body.
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- 17.2: Hormones
- Although a given hormone may travel throughout the body in the bloodstream, it will affect the activity only of its target cells; that is, cells with receptors for that particular hormone. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. Hormones play a critical role in the regulation of physiological processes because of the target cell responses they regulate.
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- 17.3: The Pituitary Gland and Hypothalamus
- The hypothalamus–pituitary complex can be thought of as the “command center” of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus–pituitary complex coordinates the messages of the endocrine and nervous systems.
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- 17.4: The Thyroid Gland
- A butterfly-shaped organ, the thyroid gland is located anterior to the trachea, just inferior to the larynx. The medial region, called the isthmus, is flanked by wing-shaped left and right lobes. Each of the thyroid lobes are embedded with parathyroid glands, primarily on their posterior surfaces. The tissue of the thyroid gland is composed mostly of thyroid follicles. The follicles are made up of a central cavity filled with a sticky fluid called colloid.
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- 17.5: The Parathyroid Glands
- The parathyroid glands are tiny, round structures usually found embedded in the posterior surface of the thyroid gland. A thick connective tissue capsule separates the glands from the thyroid tissue. Most people have four parathyroid glands, but occasionally there are more in tissues of the neck or chest. The function of one type of parathyroid cells, the oxyphil cells, is not clear. The primary functional cells of the parathyroid glands are the chief cells.
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- 17.6: The Adrenal Glands
- The adrenal glands are wedges of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule. The adrenal glands have a rich blood supply and experience one of the highest rates of blood flow in the body. They are served by several arteries branching off the aorta, including the suprarenal and renal arteries. Blood flows to each adrenal gland at the adrenal cortex and then drains into the adrenal medulla.
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- 17.7: The Pineal Gland
- Recall that the hypothalamus, part of the diencephalon of the brain, sits inferior and somewhat anterior to the thalamus. Inferior but somewhat posterior to the thalamus is the pineal gland, a tiny endocrine gland whose functions are not entirely clear. The pinealocyte cells that make up the pineal gland are known to produce and secrete the amine hormone melatonin, which is derived from serotonin.
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- 17.8: Gonadal and Placental Hormones
- This section briefly discusses the hormonal role of the gonads—the male testes and female ovaries—which produce the sex cells (sperm and ova) and secrete the gonadal hormones. The roles of the gonadotropins released from the anterior pituitary (FSH and LH) were discussed earlier.
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- 17.9: The Endocrine Pancreas
- The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach. Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas has an endocrine function. Its pancreatic islets—clusters of cells formerly known as the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide.
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- 17.10: Organs with Secondary Endocrine Functions
- In your study of anatomy and physiology, you have already encountered a few of the many organs of the body that have secondary endocrine functions. Here, you will learn about the hormone-producing activities of the heart, gastrointestinal tract, kidneys, skeleton, adipose tissue, skin, and thymus.
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- 17.11: Development and Aging of the Endocrine System
- The endocrine system arises from all three embryonic germ layers. The endocrine glands that produce the steroid hormones, such as the gonads and adrenal cortex, arise from the mesoderm. In contrast, endocrine glands that arise from the endoderm and ectoderm produce the amine, peptide, and protein hormones. The pituitary gland arises from two distinct areas of the ectoderm: the anterior pituitary gland arises from the oral ectoderm, whereas the posterior pituitary gland arises from the neural ect


16.6: Ethical Practices in Accounting
What you’ll learn to do: discuss the importance of ethical practices in accounting and the implications of unethical behavior
In this section you’ll learn why ethical accounting practices are so important and what happens when they aren’t ethical.
Learning Objectives
- Discuss the impact of the Sarbanes-Oxley Act on accounting practices
Ethics in Accounting
Due to a series of recent corporate collapses, attention has been drawn to ethical standards within the accounting profession. These collapses have caused a widespread disregard for the reputation of the accounting profession. To combat the criticism and prevent unethical and fraudulent accounting practices, various accounting organizations and governments have developed regulations and guidelines aimed at improved ethics within the accounting profession.
The following video is just one example of the type of activities that have brought the accounting profession under fire for what can best be described as questionable business practices.
Why Should an Accountant Be Ethical?
Throughout this module you have read about the wide range of people and institutions that rely on accurate accounting information to make important decisions. Despite the best efforts of FASB and GAAP, accountants and accounting firms have become increasingly “creative” in reporting the financial position of businesses and in some cases have committed outright fraud. The consequences of unethical practices in financial reporting have cost taxpayers billions of dollars, employees their jobs, and the accounting profession its untarnished reputation. Unfortunately, despite efforts by professional organizations like the AICPA and legislation by the U.S. Federal Government, there is still a subset of the accounting profession that places profit before ethics.
The AICPA Code of Professional Conduct is a collection of codified statements issued by the American Institute of Certified Public Accountants that outline a CPA’s ethical and professional responsibilities. The code establishes standards for auditor independence, integrity and objectivity, responsibilities to clients and colleagues and acts discr to the accounting profession. Unfortunately, the opening principle of the code is that membership, and therefore adherence, to the code is voluntary. This means that an accountant is never under a legal responsibility to adhere to the code and can renounce the code and membership in the AICPA at any time.
The Sarbanes-Oxley Act
Sarbanes-Oxley (SOX) was named after sponsors U.S. Senator Paul Sarbanes and U.S. Representative Michael G. Oxley. President George W. Bush signed it into law, stating that it included “the most far-reaching reforms of American business practices since the time of Franklin D. Roosevelt. The era of low standards and false profits is over; no boardroom in America is above or beyond the law.”
The bill, which contains eleven sections, was enacted as a reaction to a number of major corporate and accounting scandals, including those affecting Enron, Tyco International, Adelphia, Peregrine Systems, and WorldCom. These scandals cost investors billions of dollars when the share prices of affected companies collapsed, and shook public confidence in the U.S. securities markets.The sections of the bill cover responsibilities of a public corporation’s board of directors, adds criminal penalties for certain misconduct, and required the Securities and Exchange Commission to create regulations to define how public corporations are to comply with the law.
As a result of SOX, top management must individually certify the accuracy of financial information. In addition, penalties for fraudulent financial activity are much more severe. Also, SOX increased the oversight role of boards of directors and the independence of the outside auditors who review the accuracy of corporate financial statements. The Sarbanes-Oxley Act has been cited as a positive influence on the accounting profession for nurturing an ethical culture as it forces top management to be transparent and employees to be responsible for their acts whilst protecting whistleblowers. SOX has also been praised by a cross-section of financial industry experts, citing improved investor confidence and more accurate, reliable financial statements. The CEO and CFO are now required to unequivocally take ownership for their financial statements under Section 302, which was not the case prior to SOX.
As in any area of business, ethical practices are “good business,” but when individuals place their personal interests or wealth above those of the stakeholders, the consequences can be far reaching. It is only through the adherence to ethical reporting and GAAP that the accounting profession can regain the respect and prestige the profession once had and deserves.


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What are most drafting tables covered with?
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Vinyl
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Wood
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Metal
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Plastic wrap
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Drafting tables are adjustable in height and angle to the floor.
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True
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False
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What are T-squares used for?
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Drawing angled lines
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Drawing vertical lines
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Setting paper on a table
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Drawing horizontal lines
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Why might a set square have rabbeted edges?
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To help you prevent smudges
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To help keep your pencil sharp
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To help keep your pencil aligned
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To allow you to draw straight lines
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Checking a triangle should be done periodically.
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True
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False
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What is a set square used for?
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Drawing circles
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Drawing curved lines
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Drawing vertical and angled lines
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Drawing horizontal and angled lines
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When using a 45°-90°-45° and a 30°-60°-90° triangle, angles can be drawn every 10°.
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True
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False
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What is a protractor used for?
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Measuring lines
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Measuring angles
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Drawing angled lines
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Drawing straight lines
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What kind of line is drawn to check a triangle?
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Straight
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Parallel
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Oblique
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Perpendicular
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What is a compass used for?
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Drawing angled lines
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Drawing straight lines
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Drawing arcs and circles
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Drawing irregular curves
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What is an erasing shield used for?
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To erase mistakes
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To hold the eraser
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To erase in a desired area
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To prevent the need for erasing
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A spline is a plastic or rubber rod reinforced with metal used for drawing curves.
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True
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False
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What is the tool called a
divider
used for?
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Drawing circles
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Drawing a diameter
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Scribing arcs on metal
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Drawing arcs and curves
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What is the purpose of a scale ruler?
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To draw straight lines
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To enlarge the scale of a drawing
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To create drawings at a reduced scale
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To convert between imperial and metric measures