2.5: Testing and Selecting
- Explain the types of tests that can be administered as part of the selection process.
- Be able to discuss the types of selection models.
Besides the interview, we can also look at several other aspects that may predict success on the job. If any test is to be criteria for measuring a candidate, this should be communicated to each person interviewing, and criteria should be developed on specific test scores and expectations before interviewing and testing begins.
Testing
A variety of tests may be given upon successful completion of an interview. These employment tests can gauge a person’s KSAOs in relation to another candidate. The major categories of tests include the following:
- Cognitive ability tests
- Personality tests
- Physical ability tests
- Job knowledge tests
- Work sample
A number of written tests can be administered. A cognitive ability test can measure reasoning skills, math skills, and verbal skills. An aptitude test measures a person’s ability to learn new skills, while an achievement test measures someone’s current knowledge. Depending on the type of job, one or both will be better suited.
A cognitive ability test measures intelligences, such as numerical ability and reasoning. The Scholastic Aptitude Test (SAT) is an example of a cognitive ability test. It is important to note that some cognitive ability tests can have disparate impact. For example, in EEOC v. Ford Motor Co. and United Automobile Workers of America , African Americans were rejected from an apprentice program after taking a cognitive test known as the Apprenticeship Training Selection System (ATSS) 1 . The test showed significant disparate impact on African Americans, and it was then replaced by a different selection procedure, after costing Ford $8.55 million. Some sample test categories might include the following:
- Reasoning questions
- Mathematical questions and calculations
- Verbal and/or vocabulary skills
Aptitude tests can measure things such as mechanical aptitude and clerical aptitude (e.g., speed of typing or ability to use a particular computer program). Usually, an aptitude test asks specific questions related to the requirements of the job. To become a New York City police offer, for example, an aptitude test is required before an application will be considered. The written exam is given as a computerized test at a computerized testing center in the city. The test measures cognitive skills and observational skills (aptitude test) required for the job 2 .
Personality tests such as Meyers-Briggs and the “Big Five” personality factors may be measured and then compared with successful employee scores. For example, The University of Missouri Health Care system recently launched a patient satisfaction initiative as part of its strategic plan. The plan includes training for current employees and personality testing for nursing, managerial, and physician candidates (Silvey, 2011). The goal of the test is to assess talent and to see if the candidate has the potential to meet the expectations of patients. They hired a private company, Talent Plus, who conducts the test via phone interviews. However, many companies administer tests themselves, and some tests are free and can be administered online.
The Big Five personality test looks at extroversion, agreeableness, conscientiousness, neuroticism, and openness. Self-assessment statements might include the following:
- I have an assertive personality.
- I am generally trusting.
- I am not always confident in my abilities.
- I have a hard time dealing with change.
Some institutions also require physical ability tests; for example, to earn a position in a fire department, you may have to be able to carry one hundred pounds up three flights of stairs. If you use tests in your hiring processes, the key to making them useful is to determine a minimum standard or expectation, specifically related to the requirements of the job. An HR manager should also consider the legality of such tests. In the EEOC v. Dial Corp. case 1 , women were disproportionately rejected for entry-level positions. Prior to the test, 46 percent of hires were women, but after implementation of the test, only 15 percent of the new hires were women. The Equal Employment Opportunity Commission (EEOC) established that the test was considerably more difficult than the job, resulting in disparate impact. Physical ability tests need to show direct correlation with the job duties.
A job knowledge test measures the candidate’s level of understanding about a particular job. For example, a job knowledge test may require an engineer to write code in a given period of time or may ask candidates to solve a case study problem related to the job.
Work sample tests ask candidates to show examples of work they have already done. In the advertising business, this may include a portfolio of designs, or for a project manager, this can include past project plans or budgets. When applying for a pharmaceutical representative position, a “brag book” might be required (Hansen, 2011). A brag book is a list of recommendation letters, awards, and achievements that the candidate shares with the interviewer. Work sample tests can be a useful way to test for KSAOs. These work samples can often be a good indicator of someone’s abilities in a specific area. As always, before looking at samples, the interviewer should have specific criteria or expectations developed so each candidate can be measured fairly.
Once the interview is completed and testing occurs, other methods of checking KSAOs, including checking references, driving records, and credit history, can be performed. Some companies even use Facebook as a way of gauging the candidate’s professionalism.
Reference checking is essential to verify a candidate’s background. It is an added assurance that the candidate’s abilities are parallel with what you were told in the interview. While employment dates and job titles can be verified with previous employers, many employers will not verify more than what can be verified in the employment record because of privacy laws. However, if you do find someone who is willing to discuss more than just dates and job titles, a list of questions is appropriate. Some of these questions might include the following:
- What was the title and responsibilities of the position the candidate had while at your company?
- Do you think the candidate was qualified to assume those responsibilities?
- Does this person show up on time and have good attendance?
- Would you consider this person a team player?
- What are the three strongest and weakest characteristics of this candidate?
- Would you rehire this person?
If a candidate will be driving a company car or vehicle, such as a UPS truck, driving records may be checked. Criminal background checks may also be used if the position will include interaction with the public. If the position requires handling of money, a credit check may be required, although a written notice is required to be given to the candidate before the credit check is carried out. In addition, written permission must be provided to the credit agency, and the applicants must receive a copy of the report and a copy of their rights under the Consumer Credit Reporting Reform Act (CCRRA). All these types of tests can be used to determine if someone has been honest about their past employment.
Some companies require drug testing, which causes some debate. While some organizations say this is a safety issue (and pay lower insurance premiums), others say it is an invasion of privacy. As long as drug tests are administered for a defensible reason (safety), many organizations will continue to require them. Some organizations will also require physical examinations to ensure the candidate can perform the tasks required. A final form of testing is the honesty test. A number of “what would you do” questions are asked. The challenge with this type of test is that many people know the “right” answer but may not be honest in their responses.
| Provocative or inappropriate photos or info | 53% |
| Drinking or drug use | 44% |
| Badmouthing previous employer, colleague, or client | 35% |
| Poor communication skills | 29% |
| Discriminatory comments | 26% |
| Lied about qualifications | 24% |
| Leaked confidential information about previous job | 20% |
Source: Kit Eaton “If You’re Applying for a Job, Censor Your Facebook Page,” Fast Company , August 19, 2009, accessed January 27, 2011, www.fastcompany.com/blog/kit-eaton/technomix/if-youre-applying-job-censor-your-facebook-page.
Forty-five percent of organizations use social networking such as Facebook, Twitter, or LinkedIn to gather information about potential candidates (Eaton, 2009). See Table “Reasons Why Employers Acted upon Data Found on Social Networking Sites” for the types of data found on social networking sites that disqualified candidates, according to an article by Fast Company . This can be an effective method to see the kind of image the candidate portrays in his or her personal time.
Selection Methods
Tell Me about Yourself
How to answer that famous “tell me about yourself” question in an interview.
A clinical selection approach is probably the most common selection method, and it involves all who will be making the decision to hire a candidate. The decision makers review the data and, based on what they learn from the candidate and the information available to them, decide who should be hired for a job. Because interviewers have a different perception about the strengths of a candidate, this method leaves room for error. One consideration is disparate treatment, in which one’s biases may result in not hiring candidates based on their age, race, or gender. One way to handle this and limit the personal stereotypes and perceptions of the interviewers is to use a statistical method in hiring.
In the statistical method, a selection model is developed that assigns scores and gives more weight to specific factors, if necessary. For example, for some jobs, the ability to work in a team might be more important, while in others, knowledge of a specific computer program is more important. In this case, a weight can be assigned to each of the job criteria listed. For example, if the job is a project manager, ability to work with the client might be more important than how someone dresses for the interview. So, in the example shown in Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” , dress is weighted 1, while being able to give bad news to a client is weighted 5. In the example, the rating is multiplied by the weight to get the score for the particular job criteria. This method allows for a fairer process and can limit disparate treatment, although it may not limit disparate impact. A statistical method may work like this: you and the hiring team review the job analysis and job description and then determine the criteria for the job. You assign weights for each area and score ranges for each aspect of the criteria, rate candidates on each area as they interview, and then score tests or examine work samples. Once each hiring manager has scored each candidate, the hiring team can compare scores in each area and hopefully hire the best person in the best way. A sample candidate selection model is included in Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” .
With the statistical approach, there is more objectivity than with the clinical approach. Statistical approaches include the compensatory model, multiple cutoff model, and the multiple hurdle model. In the compensatory model, a similar method of scoring is used as the weighted model but permits a high score in an important area to make up for a lower score in another area. In our Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” example, ability to give bad news to a client might outweigh a test score. These decisions would be made before the interviews happen.
A multiple cutoff model requires that a candidate has a minimum score level on all selection criteria. In our Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” example, the candidate may be required to have a score of at least 2 out of 5 on each criteria. If this was the case, the candidate in Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” scored low on “bad news to a client,” meaning he or she wouldn’t get the job in a multiple cutoff model. In the multiple hurdle model, only candidates with high (preset) scores go to the next stages of the selection process. For example, the expectations might be to score a 4 on at least three of the items in Figure 5.4 “Sample Selection Model, with Sample Scores and Weighting Filled In” . If this were the case, this candidate might make it to the next level of the selection process, since he or she scored at least a 4 on three criteria areas.
Once the discussion on whom to hire has occurred and a person has been selected, the final phase of the process is to make an offer to the candidate. This is discussed in Section 5.5 “Making the Offer”.
- Once the interview process is complete, some companies use other means of measuring candidates. For example, work samples are an excellent way of seeing how someone might perform at your company.
- An aptitude test or achievement test can be given. An aptitude test measures how well someone might be able to do something, while an achievement test measures what the candidate already knows. Tests that measure cognitive ability and personality are examples.
- Some organizations also perform drug tests and physical tests. A physical test might consist of being able to lift a certain amount of weight, if required for the job. Honesty tests are also given; these measure the honesty level of the candidate. However, these tests may not be reliable, since someone can guess the “right” answer.
- Facebook, Twitter, and other social networking websites are also used to gather information about a candidate. Calling references is another option.
- Every person interviewing the candidate should have a selection model; this method utilizes a statistical approach as opposed to a clinical approach . The selection table lists the criteria on the left and asks interviewers to provide a rating for each. This method can allow for a more consistent way of measuring candidates.
- Develop a sample candidate selection for your current job.
- Visit your or another person’s Facebook page. Consider the content from an interviewer’s point of view. Should anything be removed or changed?
1 “Employment Tests and Selection Procedures,” US Equal Employment Opportunity Commission, accessed August 2, 2011, http://www.eeoc.gov/policy/docs/factemployment_procedures.html .
2 “Exam Schedule,” New York Police Department, accessed August 2, 2011, www.nypdrecruit.com/exam-center/exam-overview.
References
Eaton, K., “If You’re Applying for a Job, Censor Your Facebook Page,” Fast Company , August 19, 2009, accessed January 27, 2011, www.fastcompany.com/blog/kit-eaton/technomix/if-youre-applying-job-censor-your-facebook-page.
Hansen, K., “So, You Want to Get into Paramedical Sales?” n.d., Quintessential Careers, accessed August 2, 2011, www.quintcareers.com/pharmaceutical_sales_careers.html.
Silvey, J., “MU Health Care to Renew Satisfaction Effort,” Columbia Daily Tribune , August 2, 2011, accessed August 2, 2011, www.columbiatribune.com/news/2011/aug/02/mu-health-care-to-renew-satisfaction-effort/.


14.9: Nuclear Binding Energy
Explain trends in the relative stability of nuclei.
As a simple example of the energy associated with the strong nuclear force, consider the helium atom composed of two protons, two neutrons, and two electrons. The total mass of these six subatomic particles may be calculated as:
\[\underbrace{(2 \times 1.0073 \, \text{amu})}_{\text{protons}} + \underbrace{(2 \times 1.0087\, \text{amu})}_{\text{neutrons}} + \underbrace{(2 \times 0.00055\, \text{amu})}_{\text{electrons}} =4.0331\, \text{amu} \nonumber \]
However, mass spectrometric measurements reveal that the mass of an atom is 4.0026 amu, less than the combined masses of its six constituent subatomic particles. This difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound together; this is also the energy needed to break a nucleus into its constituent protons and neutrons. In comparison to chemical bond energies, nuclear binding energies are vastly greater, as we will learn in this section. Consequently, the energy changes associated with nuclear reactions are vastly greater than are those for chemical reactions.
The conversion between mass and energy is most identifiably represented by the mass-energy equivalence equation covered earlier, which results in massive amounts of energy for even tiny amounts of mass. Because the energy changes for breaking and forming bonds are so small compared to the energy changes for breaking or forming nuclei, the changes in mass during all ordinary chemical reactions are virtually undetectable. The most energetic chemical reactions exhibit enthalpies on the order of thousands of kJ/mol, which is equivalent to mass differences in the nanogram range (10 –9 g). On the other hand, nuclear binding energies are typically on the order of billions of kJ/mol, corresponding to mass differences in the milligram range (10 –3 g).
The relative stability of a nucleus is correlated with its binding energy per nucleon , the total binding energy for the nucleus divided by the number or nucleons in the nucleus. As we shall see, nuclear reactions will occur that lead towards maximizing the nuclear binding energy per nucleon. Whether this results in increasing the number of nucleons or decreasing the number of nucleons depends upon where the nucelus is on the curve shown in Figure \(\PageIndex{1}\). In the subsections which follow, we will explore each of these possibilities in more detail.
Glossary
- mass defect
- The difference between the calculated and experimentally measured masses.
- nuclear binding energy
- The energy needed to break a nucleus into its constituent protons and neutrons.
- binding energy per nucleon
- The total binding energy for the nucleus divided by the number or nucleons in the nucleus.


10.2: Design of the Flankers Experiment
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This section will provide a brief overview of the experimental design and main results from the ERP CORE flankers experiment. This experiment was designed to isolate two different ERP components, the lateralized readiness potential (LRP) and the error-related negativity (ERN).
The LRP is a negative voltage over the hemisphere contralateral to a hand that is being prepared for a response. For example if I were to tell you “raise your left pinkie,” a negative voltage would be present over the motor cortex of the right hemisphere, preceding the actual pinkie response by 100-200 ms. The LRP is related to the preparation rather than the execution of the response. For example, if I were to tell you “raise your right pinkie when I say GO,” the negative voltage over the right hemisphere would appear right away, even before I said “GO.” Like the N2pc component, the LRP is isolated with a contralateral-minus-ipsilateral difference wave (relative to the side of the response hand). For an excellent review of the LRP, see Smulders and Miller (2012).
The ERN is a negative voltage with a maximum amplitude near FCz that occurs on error trials (usually in tasks where the error is obvious to the participant). It usually begins shortly before the actual buttonpress response and peaks 50-100 ms after the response. To get a good ERN, you need participants to make enough errors that you have a decent number of trials for averaging, but not so many errors that they’re not really putting any effort into doing the task correctly. For an excellent review of the ERN, see Gehring et al. (2012).
In the ERP CORE, we used a version of the Eriksen flankers task (Eriksen, 1995) to elicit these components. In the present chapter, we’ll focus on the LRP. As illustrated in Figure 10.1.A, each stimulus array contained a central target arrow that pointed leftward or rightward with equal probability, surrounded by two flanking arrows on each side. Participants were instructed to make a rapid buttonpress response for each array, pressing with the left index finger if the central arrow pointed leftward and with the right index finger if the central arrow pointed rightward. They were instructed to ignore the flankers, which pointed in the same direction as the central target arrow on 50% of trials (called Compatible trials) and pointed in the opposite direction on the other 50% (called Incompatible trials). Each array was presented for 200 ms, and successive arrays were separated by an interstimulus interval of 1200–1400 ms. To make sure we had a good number of error trials, participants were told to speed up if they were making errors on fewer than 10% of trials and to slow down if they were making errors on more than 20% of trials.
In the ERP CORE paper (Kappenman et al., 2021), we focused our LRP and ERN analyses on ERPs that were time-locked to the response (i.e., the response rather than the stimulus was used as time zero when the data were epoched and averaged). The LRP was isolated by examining trials with left-hand versus right-hand responses. Figure 10.1.B shows the grand average ERPs, with one waveform for the ipsilateral hemisphere (C3 for left-hand response trials averaged with C4 for right-hand response trials) and another waveform for the contralateral hemisphere (C4 for left-hand response trials averaged with C3 for right-hand response trials). The LRP is a negative voltage over the contralateral hemisphere that is superimposed on the other brain activity. To isolate the LRP, we construct a contralateral-minus-ipsilateral difference wave (Figure 10.1.C). You can see that the LRP in this difference wave starts to head in a negative direction approximately 120 ms prior to the response, and it peaks shortly before the response. (The slight positive voltage in the difference wave prior to -150 ms is likely an artifact of the 0.1 Hz high-pass filter that was applied to the continuous EEG at an early step in the analysis.)
The ERN is examined by comparing trials with correct trials and trials with incorrect trials (Figure 10.1.D). A sharp negative wave is superimposed on the positive voltage that would otherwise occur, peaking shortly after the response. This is then followed by a more positive voltage on the error trials than on the correct trials (called the error positivity or P E ). The ERN and P E are often isolated from the other brain activity by making an error-minus-correct difference wave (Figure 10.1.E).
In the main LRP analyses in the ERP CORE paper (Kappenman et al., 2021), we collapsed across compatible and incompatible trials for the sake of simplicity. In the present chapter, we’re going to look at the LRP separately for these trial types, focusing on stimulus-locked instead of response-locked averages. We’ll consider only the correct trials. Many prior experiments have found that response times (RTs) are slowed on incompatible trials relative to compatible trials, and this is mainly because information about the flankers “leaks through” to response selection mechanisms. On compatible trials, this helps to activate the correct response. On incompatible trials, however, the incorrect response may be activated, which slows down the response (and often leads to errors). This can sometimes be observed in the LRP waveform, which may be contralateral to the incorrect hand briefly before becoming contralateral to the correct hand on incompatible trials (Gratton et al., 1988). In addition, the onset latency of the LRP is delayed on incompatible trials relative to compatible trials.
We didn’t do any of these analyses for the ERP CORE paper, but I thought they would be interesting to do in the present chapter. For one thing, they’ll give us an opportunity to look at several different measures of amplitude and latency. For another, we won’t know the results until we do the analyses, so there will be some drama!


1.8: Polyatomic Ions
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The compound NaOH has wide industrial use and is the active ingredient in drain cleaners. Based on the discussion in the previous section, we would expect NaOH to be an ionic compound because it contains sodium, a Group 1A metal. Hydrogen and oxygen, however, are nonmetals, and we would expect these to bond together covalently. This compound, called sodium hydroxide, is an example of an ionic compound formed between a metal ion (sodium) and a polyatomic ion (HO – ). Charged groups of atoms, like HO – , that are bonded together covalently are called polyatomic ions . Within an ionic compound a polyatomic behaves as a single unit forming salts with other cations or anions.
Using the rules described in Section 3.2 , we can draw a Lewis diagram for HO – . Oxygen has six valence electrons and hydrogen has one, for a total of seven. The central atom in our structure will be hydrogen (it is to the left of oxygen in the periodic table). Next, because this is a polyatomic ion with a single negative charge, we add the extra electron to the central atom, pair the electrons and then draw the two atoms bonded together. Next, the six remaining electrons are distributed around the oxygen to form an octet. Finally, the polyatomic ion is enclosed in brackets with the charge as a superscript to show that the ion behaves as a single unit.
Polyatomic ions are very common in chemistry. It is essential that you memorize these and be able to correlate the name, the composition and the charge for each of them, as they will be discussed freely throughout the remainder of the course and you will be expected to know these in General Chemistry.
Example \(\PageIndex{1}\):
Construct a Lewis diagram for the polyatomic ion CO 3 2 – .
Solution
Oxygen has six valence electrons and carbon has four; therefore in CO 3 2 – there will be a total of 22 valence electrons, plus two additional electrons from the 2- charge. The central atom in our structure will be carbon (it is to the left of oxygen in the periodic table). Next, we draw the carbon (our central atom) with its’ four electrons and add the additional two electrons from the charge. The three oxygens are placed around the carbon and the electrons are arranged to form the three covalent bonds. Next, the 18 remaining electrons are distributed around the oxygens so that they all have a full octet. The carbon, however, is only surrounded by six electrons. To remedy this, we move one electron pair in to form a double bond to one of the oxygen atoms. Finally, the polyatomic ion is enclosed in brackets with the charge as a superscript.
We need to understand that the process of placing electrons into a particular bond in a compound is an artificial aspect of building Lewis diagrams. In fact, the electrons are added to the polyatomic ion, but it is impossible to know exactly where they went.
Exercise \(\PageIndex{1}\)
- Draw Lewis diagrams for NO 2 - and NH 4 + .


4.6: Diseases and Disorders of the Respiratory System
This section provides an overview of common respiratory disorders and diseases.
Allergies
Allergies (ĂL-ĕr-jēz) occur when a person’s immune system reacts to a substance and makes antibodies that identify that substance as harmful. Substances identified as allergens can cause inflammation of the skin, sinuses, nasal passages, airways, or digestive system. The severity of allergies varies from person to person and can range from minor irritation to a potentially life-threatening emergency called anaphylaxis (ăn-ă-fĭ-LĂK-sĭs). While most allergies can’t be cured, allergy medications can help relieve symptoms. [1]
There are many types of allergies. Allergic rhinitis, commonly referred to as “hay fever,” can cause sneezing; pruritus (PRŪ-rī-tŭs), itching of the skin, as well as itching of the nose, eyes, or roof of the mouth; rhinorrhea; and watery, red, or swollen eyes. A food allergy can cause tingling in the mouth; swelling of the lips, tongue, face, or throat; hives; and anaphylaxis. Read more information about anaphylaxis in the following subsection. An insect sting allergy can cause swelling at the sting site, itching or hives all over the body, cough, chest tightness, wheezing, shortness of breath, and anaphylaxis. A drug allergy can cause hives, pruritus, rash, swelling in the respiratory tract, and anaphylaxis.
Anaphylaxis
Severe allergies, including allergies to foods, insect stings, medications, and blood transfusions, can trigger a severe reaction known as anaphylaxis. As a life-threatening medical emergency, anaphylaxis can cause a patient to go into anaphylactic shock, a potentially fatal condition. Signs and symptoms of anaphylaxis are as follows [2] :
-
View the following YouTube video
[10]
for additional information about asthma:
How Does Asthma Work? – Christopher E. Gaw
Bronchitis
Often developing from a cold or other respiratory infection, acute bronchitis is very common. Acute bronchitis, also called a chest cold, usually improves within a week to ten days without lasting effects, although the cough may linger for weeks.
Chronic bronchitis (KRŎN-ĭk brŏng-KĪ-tĭs), a more serious condition, is a constant irritation or inflammation of the lining of the bronchial tubes, often due to smoking. Chronic bronchitis is one of the conditions included in chronic obstructive pulmonary disease (COPD). [11] Read more about COPD in the following subsection.
Symptoms for either acute bronchitis or chronic bronchitis may include the following:
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Symptoms of a common cold usually appear one to three days after exposure to a cold-causing virus. Signs and symptoms, which can vary from person to person, are as follows
[16]
:
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After smoking, radon is the second leading cause of lung cancer in the United States. Radon is a naturally occurring gas that forms in rocks, soil, and water. It cannot be seen, tasted, or smelled. When radon gets into homes or buildings through cracks or holes, it can get trapped and build up in the air inside. People who live or work in these homes and buildings breathe in high radon levels. Over long periods of time, radon can cause lung cancer.
[22]
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Tuberculosis (tū-bĕr-kyŭ-LŌ-sĭs)
(TB)
is a serious infectious disease that affects the lungs. It is caused by bacteria that can be spread through the air from person to person. Symptoms include a chronic cough,
hemoptysis
(hē-MŎP-tĭ-sĭs) or coughing up blood, weight loss, night sweats, and fever. Patients with TB require a long course of treatment involving multiple antibiotics.
[32]
- Mayo Clinic Staff. (2022, August 5). Allergies. www.mayoclinic.org/diseases-conditions/allergies/symptoms-causes/syc-20351497 ↵
- Mayo Clinic. (2021). Anaphylaxis . www.mayoclinic.org/diseases-conditions/anaphylaxis/symptoms-causes/syc-20351468 ↵
- This work is a derivative of Anatomy and Physiology by OpenStax licensed under CC BY 4.0. Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction ↵
- “ Asthma_attack-illustration_NIH.jpg ” by United States-National Institute of Health: National Heart, Lung, Blood Institute is in the Public Domain ↵
- This work is a derivative of Anatomy and Physiology by OpenStax licensed under CC BY 4.0. Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction ↵
- This work is a derivative of Anatomy and Physiology by OpenStax licensed under CC BY 4.0. Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction ↵
- “ Ventolin® HFA (Albuterol Sulfate) Inhaler.jpg ” by MisterNarwhal is licensed under CC BY SA 4.0 ↵
- “Albuterol 2.jpg” by Mark Oniffrey is licensed under CC BY SA 4.0 ↵
- “Nebulizer_Mouthpiece.png” by BruceBlaus is licensed under CC BY-SA 4.0 ↵
- TED-Ed. (2017, May 11). How does asthma work? - Christopher E. Gaw [Video]. YouTube. https://youtu.be/PzfLDi-sL3w ↵
- Mayo Clinic Staff. (2017, April 11). Bronchitis. www.mayoclinic.org/diseases-conditions/bronchitis/symptoms-causes/syc-20355566 ↵
- “ Copd 2010Side.JPG ” by National Heart, Lung, and Blood Institute is licensed in the Public Domain. ↵
- Centers for Disease Control and Prevention. (2023, June 30). What is COPD? https://www.cdc.gov/copd/index.html ↵
- Mayo Clinic Staff. (2020, April 15). COPD . https://www.mayoclinic.org/diseases-conditions/copd/symptoms-causes/syc-20353679 ↵
- This work is a derivative of Anatomy and Physiology by OpenStax licensed under CC BY 4.0. Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction ↵
- Mayo Clinic Staff. (2023, May 24). Common cold. www.mayoclinic.org/diseases-conditions/common-cold/symptoms-causes/syc-20351605 ↵
- Centers for Disease Control and Prevention. (n.d.). COVID-19. https://www.cdc.gov/coronavirus/2019-ncov/ ↵
- Centers for Disease Control and Prevention. (2022, May 9). Cystic fibrosis. www.cdc.gov/genomics/disease/cystic_fibrosis.htm ↵
- Centers for Disease Control and Prevention. (2022, October 3). Flu symptoms & complications. https://www.cdc.gov/flu/symptoms/symptoms.htm ↵
- Centers for Disease Control and Prevention. (2023, July 31). What is lung cancer? www.cdc.gov/cancer/lung/basic_info/what-is-lung-cancer.htm ↵
- Centers for Disease Control and Prevention. (2023, July 31). What is lung cancer? www.cdc.gov/cancer/lung/basic_info/what-is-lung-cancer.htm ↵
- Centers for Disease Control and Prevention. (2023, July 31). What are the risk factors for lung cancer? www.cdc.gov/cancer/lung/basic_info/risk_factors.htm ↵
- Centers for Disease Control and Prevention. (2023, July 31). What are the symptoms of lung cancer? www.cdc.gov/cancer/lung/basic_info/symptoms.htm ↵
- Slowik, J. M., Sankari, A., & Collen, J. F. (2022). Obstructive sleep apnea. [Updated 2022 Dec 11]. In: StatPearls [Internet]. www.ncbi.nlm.nih.gov/books/NBK459252/ ↵
- “Obstruction ventilation apnée sommeil.svg” by Habib M’henni is in the Public Domain. ↵
- American Lung Association. (2023, August 3). Pneumonia symptoms and diagnosis. https://www.lung.org/lung-health-diseases/lung-disease-lookup/pneumonia/symptoms-and-diagnosis ↵
- “Sputum.JPG” by Zhangmoon618 is licensed under CC0 ↵
- Centers for Disease Control and Prevention. (2022, September 30). Causes of pneumonia . www.cdc.gov/pneumonia/causes.html ↵
- “Incentive Spirometer.pngsommeil.svg” by BruceBlaus is licensed under CC BY-SA 4.0 ↵
- Cleveland Clinic. (2022). Pulmonary embolism. my.clevelandclinic.org/health/diseases/17400-pulmonary-embolism ↵
- Centers for Disease Control and Prevention. (2023). Respiratory syncytial virus. https://www.cdc.gov/rsv/about/symptoms.html ↵
- Centers for Disease Control and Prevention. (2023). Tuberculosis. www.cdc.gov/tb/default.htm ↵
- Centers for Disease Control and Prevention. (2020, May 6). CDC tuberculosis (TB) transmission and pathogenesis video [Video]. YouTube. All rights reserved. https://youtube.com/watch?v=UKV8Zn7x0wM ↵
-
Tuberculosis (tū-bĕr-kyŭ-LŌ-sĭs)
(TB)
is a serious infectious disease that affects the lungs. It is caused by bacteria that can be spread through the air from person to person. Symptoms include a chronic cough,
hemoptysis
(hē-MŎP-tĭ-sĭs) or coughing up blood, weight loss, night sweats, and fever. Patients with TB require a long course of treatment involving multiple antibiotics.
[32]
-
After smoking, radon is the second leading cause of lung cancer in the United States. Radon is a naturally occurring gas that forms in rocks, soil, and water. It cannot be seen, tasted, or smelled. When radon gets into homes or buildings through cracks or holes, it can get trapped and build up in the air inside. People who live or work in these homes and buildings breathe in high radon levels. Over long periods of time, radon can cause lung cancer.
[22]
-
Symptoms of a common cold usually appear one to three days after exposure to a cold-causing virus. Signs and symptoms, which can vary from person to person, are as follows
[16]
:


13.8B: Antiprotozoan and Antihelminthic Drugs
- Describe the objective of drugs against helminths anf the disadvantages to developing drugs against protozoa
Parasites are organisms that live on or in a host organism to obtain food. Two major classes of parasitic organisms include protozoa and helminths.
Protozoa are unicellular eukaryotic organisms that are classified as either free-living or parasitic organisms. Protozoa are further classified based on their mode of locomotion and include: Sarcodina (amoeba); Mastigophora (flagellates); Ciliophora (ciliates); and Sporozoa (non motile in adult form). Some examples of diseases caused by protozoa include: Malaria, Giardia, Trichomoniasis, and Leishmaniasis.
Helminths are multicellular eukaryotic organisms that are also classified as either free-living or parasitic chemoheterotrophic organisms. Helminths are parasitic worms and are divided into three major groups including: flatworms (platyhelminths); thorny-headed worms (acanthocephalins); and roundworms (nematodes and hookworms).
The variation that exists between protozoa contributes to complications associated with developing effective drugs. The lack of similarities between protozoans demands the need for highly specific drugs and medications against individual pathogens. In addition, protozoa are eukaryotic and exhibit similar properties and metabolic pathways as human cells. Therefore, the drugs that are developed to target protozoans are classified by either their mechanism of action or the organism for which they target. In terms of mechanism of actions, most antiprotozoan drugs specifically target the organism to prevent its growth and reproduction.
Protozoal diseases can also be prevented by targeting the route of transmission and/or targeting vector organisms. For example, Malaria is caused by the protozoan Plasmodia. This parasite is injected into humans via mosquitoes. The development of antimalarial drugs are based on the life cycle of Plasmodiain both the mosquito and human host.
Other types of antiprotozan drugs specifically target metabolic mechanisms utilized by the parasite. For example, African sleeping sickness is caused by trypanosomes. The drug Eflornithine attacks this parasite by targeting an enzyme responsible for regulating cell division.
Helminths are characterized as various types of parasitic worms, which are effectively targeted by promoting expulsion from the body. Parasitic helminths worms include: tapeworms, flukes, leeches and hookworms. The drugs utilized to target helminths are characterized based on chemical structure and mechanism of action. A few examples of the major drug classes include: piperazine, benzimidazole, levamisole, pyrantel, morantel and emodepside.
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Key Points
- Antiprotozoan drugs are typically species specific.
- It is essential that antiprotozoan drugs target pathways and mechanisms specific to protozoa as overlap in the basic biology can result in inaccurate targeting of the drug to both the host and protozoa.
- Antihelminthic drugs typically focus on the disruption of structural mechanisms that maintain body structure resulting in paralysis of the helminth which promotes expulsion.
Key Terms
- helminth : A parasitic roundworm or flatworm.
- protozoa : Protozoa are a diverse group of unicellular eukaryotic organisms, many of which are motile. Originally, protozoa had been defined as unicellular protists with animal-like behavior, e.g., movement. Protozoa were regarded as the partner group of protists to protophyta, which have plant-like behavior, e.g., photosynthesis.
- Parasite : Parasitism is a non-mutual relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host.


1.1E: Describing Relationships Between Two Quantities With Functions (Exercises)
Section 1.1 Exercises
-
Select all of the following tables which represent \(y\) as a function of \(x\).
-
Select all of the following tables which represent \(y\) as a function of \(x\).
-
Select all of the following tables which represent \(y\) as a function of \(x\).
-
Select all of the following tables which represent \(y\) as a function of \(x\).
-
Select all of the following graphs which represent \(y\) as a function of \(x\).
a b c
d e f -
Select all of the following graphs which represent \(y\) as a function of \(x\).
a b c
d e f - Is the sales tax on an item in California a function of the price of the item?
- Is the daily high temperature of Clovis, California a function of the date?
- Is the date a function of the daily high temperature of Clovis, California?
-
Determine if the following equations represent a function
- \(5x-2y=10\)
- \(3x^2+2y^2=1\)
- \(3x-\sqrt{y}=10\)
-
Determine if the following equations represent a function
- \(3x+5y=10\)
- \(y^2=x\)
- \(\dfrac{3x}{y-2}=3\)
- Given the graph of the function \(f(x)\) below (a) Evaluate \(f(1)\) (b) Evaluate \(f(3)\) (c) Find all values of x where \(f(x)=3\)
- Given the graph of the function \(g(x)\) below (a) Evaluate \(g(1)\) (b) Evaluate \(g(3)\) (c) Find all values of x where \(g(x)=3\)
-
Given the function \(g(x)\) graphed here,
a. Evaluate \(g(2)\)
b. Solve \(g(x) = 2\)
-
Given the function \(f(x)\) graphed here,
a. Evaluate \(f(4)\)
b. Solve \(f(x) = 4\)
-
Based on the table below,
a. Evaluate \(f(3)\) b. Solve \(f(x) = 1\)\(x\) 0 1 2 3 4 5 6 7 8 9 \(f(x)\) 74 28 1 53 56 3 36 45 14 47 -
Based on the table below,
a. Evaluate \(f(8)\) b. Solve \(f(x) = 1\)\(x\) 0 1 2 3 4 5 6 7 8 9 \(f(x)\) 62 8 7 38 86 73 70 39 75 34 -
Let \(f(x) = 4 - 2x\) and \(g(x) = 8x^2 - 7x + 3\).
- Evaluate \(f(2)\)
- Evaluate \(g(2)\)
- Evaluate \(f(-1)\)
- Evaluate \(g(-1)\)
- Find all values of \(x\) where \(f(x)=0\)
- Evaluate \(f(5)-f(3)\)
- Evaluate \(\dfrac{g(2)-g(1)}{2-1}\)
-
Let \(h(x) = 8 - 3x\) and \(k(x) = 6x^2 - 7x + 4\).
- Evaluate \(h(3)\)
- Evaluate \(k(3)\)
- Evaluate \(h(-2)\)
- Evaluate \(k(-2)\)
- Find all values of \(x\) where \(h(x)=0\)
- Evaluate \(h(4)+h(1)\)
- Evaluate \(\dfrac{k(4)-k(1)}{4-1}\)
-
Let \(f(x) = -x^3 + 2x\) and \(g(x) = 3 + \sqrt{x + 3}\)
- Evaluate \(f(4)\)
- Evaluate \(g(4)\)
- Evaluate \(f(-4)\)
- Evaluate \(g(-4)\)
- Find all values of \(x\) where \(g(x)=0\)
- Evaluate \(f(6)-f(1)\)
- Evaluate \(\dfrac{g(6)-g(1)}{6-1}\)
-
Let \(m(x) = 5x^4 + x^2\) and \(n(x) = 4 - \sqrt[3]{x - 2}\)
- Evaluate \(m(3)\)
- Evaluate \(n(3)\)
- Evaluate \(m(-2)\)
- Evaluate \(n(2)\)
- Find all values of \(x\) where \(n(x)=0\)
- Evaluate \(n(10)+n(1)\)
- Evaluate \(\dfrac{m(4)-m(1)}{4-1}\)
-
Let \(f(x) = \dfrac{x - 3}{x + 1}\)
- Evaluate \(f(4)\)
- Evaluate \(f(0)\)
- Evaluate \(f(-1)\)
- Find all values of \(x\) where \(f(x)=0\)
- Evaluate \(f(4)+f(2)\)
-
Let \(f(x) = 3x+2\). Evaluate and simplify each of the following
-
\(f(a)\)
-
\(f(a+h)\)
-
\(\dfrac{f(x)-f(a)}{x-a}\)
-
\(\dfrac{f(a+h)-f(a)}{h}\)
-
-
Let \(g(x) = x^2+7\). Evaluate and simplify each of the following
-
\(g(a)\)
-
\(g(a+h)\)
-
\(\dfrac{g(x)-g(a)}{x-a}\)
-
\(\dfrac{g(a+h)-g(a)}{h}\)
-
-
Let \(f(x) = x^2+5x\). Evaluate and simplify each of the following
-
Evaluate \(f(a+h)\)
-
Evaluate \(\dfrac{f(a+h)-f(a)}{h}\)
-
-
Let \(f(x) = 3x^2-4x+2\).
-
Evaluate and simplify \(\dfrac{f(a+h)-f(a)}{h}\)
-
- Let \(f(x) = \dfrac{1}{x}\). Evaluate and simplify \(\dfrac{f(x)-f(a)}{x-a}\).
-
Let \(f(t)\) be the number of ducks in a lake
t
years after 1990. Explain the meaning of each statement:
a. \(f\left(5\right)=30\) b. \(f\left(10\right)=40\) -
Let \(h(t)\) be the height above ground, in feet, of a rocket
t
seconds after launching. Explain the meaning of each statement:
a. \(h(1)=200\) b. \(h(2)=350\) -
The amount of garbage,
G
, produced by a city with population
p
is given by \(G = f(p)\).
G
is measured in tons per week, and \(p\) is measured in thousands of people. a. The town of Tola has a population of 40,000 and produces 13 tons of garbage each week. Express this information in terms of the function \(f\).
b. Explain the meaning of the statement \(f(5)=2\). -
The number of cubic yards of dirt,
D
, needed to cover a garden with area
a
square feet is given by \(D=g(a)\). a. A garden with area 5000 ft \({}^{2}\) requires 50 cubic yards of dirt. Express this information in terms of the function \(g\).
b. Explain the meaning of the statement \(g(100)=1\). -
Dave leaves his office in Padelford Hall on his way to teach in Gould Hall. Below are several different scenarios. In each case, sketch a plausible (reasonable) graph of the function \(s = d(t)\) which keeps track of Dave’s distance
s
from Padelford Hall at time \(t\). Take distance units to be “feet” and time units to be “minutes.” Assume Dave’s path to Gould Hall is long a straight line which is 2400 feet long. [UW]
a. Dave leaves Padelford Hall and walks at a constant spend until he reaches Gould Hall 10 minutes later.
b. Dave leaves Padelford Hall and walks at a constant speed. It takes him 6 minutes to reach the half-way point. Then he gets confused and stops for 1 minute. He then continues on to Gould Hall at the same constant speed he had when he originally left Padelford Hall.
c. Dave leaves Padelford Hall and walks at a constant speed. It takes him 6 minutes to reach the half-way point. Then he gets confused and stops for 1 minute to figure out where he is. Dave then continues on to Gould Hall at twice the constant speed he had when he originally left Padelford Hall.
d. Dave leaves Padelford Hall and walks at a constant speed. It takes him 6 minutes to reach the half-way point. Then he gets confused and stops for 1 minute to figure out where he is. Dave is totally lost, so he simply heads back to his office, walking the same constant speed he had when he originally left Padelford Hall.
e. Dave leaves Padelford heading for Gould Hall at the same instant Angela leaves Gould Hall heading for Padelford Hall. Both walk at a constant speed, but Angela walks twice as fast as Dave. Indicate a plot of “distance from Padelford” vs. “time” for the both Angela and Dave.
f. Suppose you want to sketch the graph of a new function \(s = g(t)\) that keeps track of Dave’s distance s from Gould Hall at time t. How would your graphs change in (a) - (e)? -
Match each story about a bike ride with the appropriate graph, where \(d\) represents the distance from home \(t\) hours since the start of the ride.
- The rider starts from home and rides 5 miles per hour away from home
- The rider starts 5 miles from home and rides 5 miles per hour away from home.
- The rider starts 5 miles from home and rides 10 miles per hour away from home.
-
The rider starts 10 miles from home and rides 5 miles per hour towards their home.
- III. V.
- VI.
- Answer
-
1. Tables (a) and (b) represent \(y\) as a function of \(x\) because for every value of \(x\) there is only one value for \(y\). Table (c) is not a function because for the input \(x = 10\), there are two different outputs for \(y\).
3. Tables (a) (b) and (d) represent \(y\) as a function of \(x\) because for every value of \(x\) there is only one value for \(y\). Table (c) is not a function because for the input \(x=3\), there are two different outputs for \(y\). Even though the input \(x = 3\) is listed twice in table (a), it is associated with only one output \(y =1\).
5. Graphs (a) (b) (d) and (e) represent \(y\) as a function of \(x\) because for every value of \(x\) there is only one value for \(y\). Graphs (c) and (f) are not functions because they contain points that have more than one output for a given input, or values for \(x\) that have 2 or more values for \(y\).
7. Yes, the sales tax on an item in California a function of the price of the item. For each price, there is exactly one tax charged since sales tax is typically a percentage of the price.
9. No, the date a function of the daily high temperature of Clovis, California. Two different days may have the same daily high temperature.
11. (a) Yes, the equation does represent a function since the equation can be written as a single formula for \(y\) where \(y=\dfrac{-3}{5}x+2\).
(b) No, the equation doesn't represent a function since the equation can't be written as a single formula for \(y\) where \(y=\pm \sqrt{x}\).
(c) (a) Yes, the equation does represent a function since the equation can be written as a single formula for \(y\) where \(y=\dfrac{3}{2}x+2\).
13. (a) \(g(1)=3\) (b) \(g(3)=-1\) (c) \(x=1\) and \(x=1\)
15. (a) \(f(4) = 1\) (b) \(x = -2\)
17. (a) \(f(8) = 75\) (b) There is no solution to \(f(x) = 1\)
19. (a) \(h(3)-1\) (b) \(k(3)=37\) (c) \(h(-2)= 14\) (d) \(k(-2)=42\) (e) \(x=\dfrac{-8}{3}\) (f) \(h(4)+h(1)=1\) (g) \(\dfrac{k(4)-k(1)}{4-1}=23\)
21. (a) \(m(3)=414\) (b) \(n(3)=3\) (c) \(m(-2)=84\) (d) \(n(2)=4\) (e) \(x=66\) (f) \(n(10)+n(1)=7\) (g) \(\dfrac{m(4)-m(1)}{4-1}=430\)
23.(a) \(f(a)=3a+2\) (b) \(f(a+h)=3a+3h+2\) (c) \(\dfrac{f(x)-f(a)}{x-a}= 3\) (d) \(\dfrac{f(a+h)-f(a)}{h} =3 \)
25. (a) \(f(a+h)=a^2+2ah+h^2+5a+5h\) (b) \(\dfrac{g(a+h)-g(a)}{h} = 2a+h+5\)
27. \(\dfrac{f(x)-f(a)}{x-a}=\dfrac{-1}{ax}\)
29. (a) After 1 second, the height of the rocket is 200 ft. (b) After 2 seconds, the height of the rocket is 350 ft.
31. (a) \(g(5000)=50\) (b) A garden with area 100 ft \({}^{2}\) requires 1 cubic yards of dirt.
33. (a) Graph II (b) Graph V (c) Graph I (d) Graph III


33.8: Animal Primary Tissues - Loose, Fibrous, and Cartilage Connective Tissues
- Distinguish between the different types of connective tissue
Connective Tissues
Connective tissues are composed of a matrix consisting of living cells and a non-living substance, called the ground substance. The ground substance is composed of an organic substance (usually a protein) and an inorganic substance (usually a mineral or water). The principal cell of connective tissues is the fibroblast, an immature connective tissue cell that has not yet differentiated. This cell makes the fibers found in nearly all of the connective tissues. Fibroblasts are motile, able to carry out mitosis, and can synthesize whichever connective tissue is needed. Macrophages, lymphocytes, and, occasionally, leukocytes can be found in some of the tissues, while others may have specialized cells. The matrix in connective tissues gives the tissue its density. When a connective tissue has a high concentration of cells or fibers, it has a proportionally-less-dense matrix.
The organic portion, or protein fibers, found in connective tissues are either collagen, elastic, or reticular fibers. Collagen fibers provide strength to the tissue, preventing it from being torn or separated from the surrounding tissues. Elastic fibers are made of the protein elastin; this fiber can stretch to one and one half of its length, returning to its original size and shape. Elastic fibers provide flexibility to the tissues. Reticular fibers, the third type of protein fiber found in connective tissues, consist of thin strands of collagen that form a network of fibers to support the tissue and other organs to which it is connected.
Loose (Areolar) Connective Tissue
Loose connective tissue, also called areolar connective tissue, has a sampling of all of the components of a connective tissue. Loose connective tissue has some fibroblasts, although macrophages are present as well. Collagen fibers are relatively wide and stain a light pink, while elastic fibers are thin and stain dark blue to black. The space between the formed elements of the tissue is filled with the matrix. The material in the connective tissue gives it a loose consistency similar to a cotton ball that has been pulled apart. Loose connective tissue is found around every blood vessel, helping to keep the vessel in place. The tissue is also found around and between most body organs. In summary, areolar tissue is tough, yet flexible, and comprises membranes.
Fibrous Connective Tissue
Fibrous connective tissues contain large amounts of collagen fibers and few cells or matrix material. The fibers can be arranged irregularly or regularly with the strands lined up in parallel. Irregularly-arranged fibrous connective tissues are found in areas of the body where stress occurs from all directions, such as the dermis of the skin. Regular fibrous connective tissue is found in tendons (which connect muscles to bones) and ligaments (which connect bones to bones).
Cartilage
Cartilage is a connective tissue. The cells, called chondrocytes (mature cartilage cells), make the matrix and fibers of the tissue. Chondrocytes are found in spaces within the tissue called “lacunae. ”
A cartilage with few collagen and elastic fibers is hyaline cartilage. The lacunae are randomly scattered throughout the tissue and the matrix takes on a milky or scrubbed appearance with routine stains. Sharks have cartilaginous skeletons, as does nearly the entire human skeleton during some pre-birth developmental stages. A remnant of this cartilage persists in the outer portion of the human nose. Hyaline cartilage is also found at the ends of long bones, reducing friction and cushioning the articulations of these bones.
Elastic cartilage has a large amount of elastic fibers, giving it tremendous flexibility. The ears of most vertebrate animals contain this cartilage, as do portions of the larynx, or voice box. In contrast, fibrocartilage contains a large amount of collagen fibers, giving the tissue tremendous strength. Fibrocartilage comprises the intervertebral discs in vertebrate animals, which must withstand a tremendous amount of stress. Cartilage can also transform from one type to another. For example, hyaline cartilage found in movable joints, such as the knee and shoulder, often becomes damaged as a result of age or trauma. Damaged hyaline cartilage is replaced by fibrocartilage, resulting in “stiff” joints.
Key Points
- Fibroblasts are cells that generate any connective tissue that the body needs, as they can move throughout the body and can undergo mitosis to create new tissues.
- Protein fibers run throughout connective tissue, providing stability and support; they can be either collagen, elastic, or reticular fibers.
- Loose connective tissue is not particularly tough, but surrounds blood vessels and provides support to internal organs.
- Fibrous connective tissue, which is composed of parallel bundles of collagen fibers, is found in the dermis, tendons, and ligaments.
- Hyaline cartilage forms the skeleton of the embryo before it is transformed into bone; it is found in the adult body at the tip of the nose and around the ends of the long bones, where it prevents friction at the joints.
- Fibrocartilage is the strongest of the connective tissues; it is found in regions of the body that experience large amounts of stress and require a high degree of shock absorption, such as between the vertebrae.
Key Terms
- chondrocyte : a cell that makes up the tissue of cartilage
- motile : having the power to move spontaneously
- fibroblast : a cell found in connective tissue that produces fibers, such as collagen


1.13: Gram Stain
- Use aseptic techniques in the safe inoculation of various forms of media.
- Follow oral and written instructions and manage time in the lab efficiently.
- Use the bright field light microscope to view microbes under oil immersion, make accurate observations and appropriate interpretations and store the microscope according to lab procedures.
- Properly prepare a bacterial smear for accurate staining and describe the chemical basis for simple staining and negative staining.
Differential staining distinguishes organisms based on their interactions with multiple stains. In other words, two organisms may appear to be different colors. Differential staining techniques commonly used in clinical settings include Gram staining, acid-fast staining, endospore staining, flagella staining, and capsule staining. This link to the OpenStax Microbiology text provides more detail on these differential staining techniques.  It was developed by Danish microbiologist Hans Christian Gram in 1884 as an effective method to distinguish between bacteria containing the two most common types of cell walls. (OpenStax CNX, 2018) One type consists of an inner plasma membrane and a thick outer layer of peptidoglycan. The other type consists of a double phospholipid bilayer with a thin layer of peptidoglycan between the two. The Gram Staining technique remains one of the most frequently used staining techniques.
- First, crystal violet , the primary stain , is applied to a heat-fixed smear, giving all of the cells a purple color. You will recall that crystal violet is a basic stain (excess OH- ions). It adheres to the cell because the positively charged chromogen is attracted to the negatively charged cell as described in the Simple Staining exercise. (See figures 2 and 3.) This step is chemically identical to simple staining.
- Next, Gram’s iodine , a mordant , is added. A mordant is a substance used to set or stabilize stains or dyes; in this case, Gram’s iodine acts like a trapping agent that complexes with the crystal violet, making the crystal violet–iodine complex clump and stay contained in thick layers of peptidoglycan in the cell walls. All the cells become a deep purple color after this step.
- Next, a decolorizing agent is added, usually ethanol or an acetone/ethanol solution. Cells that have thick peptidoglycan layers in their cell walls are much less affected by the decolorizing agent; they generally retain the crystal violet dye and remain purple. These are termed Gram positive . In the cells with the thin layer of peptidoglycan, the decolorizing agent easily washes the dye out of cells leaving them colorless. Cells that do not retain the CV-I are called Gram negative . Because the reagent reacts differently depending on the cell wall, this step makes Gram staining differential and is the most crucial.
- Finally, a secondary counterstain , usually safranin , is added. This stains the decolorized cells pink. (OpenStax CNX, 2018) Like the primary stain, the counterstain step is chemically a simple stain. Its purpose is to make the colorless cells visible. The safranin chromogen actually adheres to all the cells. Because the Gram positive cells are retaining the dark purple CV-I complex, the pink safranin only shows up in the colorless cells.
- After crystal violet is added, all cells are purple.
Iodine, the mordant, intensifies the color.
After decolorizing, Gram negative cells are colorless and Gram positive cells remain purple.
The counterstain imparts color to the colorless cells as a simple basic stain.
There are several important considerations in interpreting the results of a Gram stain. First, older bacterial cells may have damage to their cell walls. This is accentuated in Gram positive cells because the thick peptidoglycan begins to break down and cannot retain the CV-I complex as efficiently. The result? Gram positive cells appear pink and may be misidentified as Gram-negative. Thus, it is essential to use fresh (24 hour) bacterial cultures for Gram staining.
Second, errors, especially decolorizing too long, can affect the results. (OpenStax CNX, 2018) If exposed to the decolorizer too long, the CV-I complex can be removed from Gram positive cells along with Gram negative cells making all types appear pink at the end. Conversely, if the decolorizer is not applied long enough, the CV-I complex will remain in the Gram negative cells and they will appear purple and can be misidentified as Gram positive. This is the most common mistake students make in Gram staining. Always do a control smear when Gram staining an unknown culture to verify that your technique is correct. Getting the decolorizing step correct is tricky and takes some practice. (OpenStax CNX, 2018)
The third cause of inaccurate Gram staining is a thick smear. If cells are clumped together on the slide, the cells will not make contact with each of the reagents equally. Some individual cells may not be decolorized enough and remain purple when other identical cells become decolorized. This will result in some cells in a pure culture smear appearing different from others. (OpenStax CNX, 2018)
Besides their differing interactions with dyes and decolorizing agents, the chemical differences between Gram-positive and Gram-negative cells have other implications with clinical relevance. For example, Gram staining can help clinicians classify bacterial pathogens in a sample into categories associated with specific properties. Gram-negative bacteria tend to be more resistant to certain antibiotics than gram-positive bacteria. (OpenStax CNX, 2018)
Gram Stain Procedure
- Place a smear or drop of culture on a slide and allow to completely air dry.
- Heat-fix the slide by drawing it quickly over the flame of a Bunsen burner.
- Put a few drops of crystal violet on the fixed culture and allow to sit for one minute.
- Gently rinse with distilled water over a sink.
- Add Gram’s iodine to the fixed culture. Allow to sit for one minute. By discarding the first few drops of iodine, you ensure that the mordant is not diluted by excess water drops left on the slide from the previous rinse.
- Gently rinse with distilled water.
- Apply Gram’s Decolorizer to the slide until the stain stops coming off the slide and the decolorizer runs clear. This only takes 3-4 passes across the slide.
- Immediately, rinse with distilled water, gently. This will stop the decolorizing process.
- Apply the counterstain, safranin and allow it to sit for one minute.
- Gently rinse with distilled water.
- Gently blot in a fairly clean area of a bibulous paper book. Refrain from blotting after each rinse step. This is unnecessary and may result in the loss of cells from the slide making the few that are left more difficult to find.
In this exercise you will stain a slide with 2 smears. On one side of the slide you will place a mixed culture containing E. coli , a known Gram negative rod and on the other side Staphylococcus epidermidis , a known Gram positive coccus. You will know you have stained the slide correctly if all the rods are pink and all the cocci are purple. Be sure you are looking for cell morphology and color. If you are not tuning into the details you may not interpret your results accurately. For example, in a cursory glance you may see both colors, but a closer look may reveal an unevenly stained slide with a clumped mass of cells (where you cannot distinguish individual cell morphology) retaining the purple color and individual cells, both rods and cocci, staining pink.
Materials per studen
1 Microscope slide
1 bottle Crystal violet stain
1 bottle Gram’s iodine
1 bottle Gram’s Decolorizer
1 bottle Safranin stain Sterile toothpicks
Bibulous paper, Bunsen burner, Striker, Inoculating loop
Cultures
E. coli
Staphylococcus epidermidis
Procedure
- On the left side side, aseptically make a smear with the E. coli . Be sure to sterilize your loop after spreading cells on one slide and before getting more cells . Be sure to make the smear about the size of a nickel.
- On the right side of the slide, aseptically make a smear with the Staphylococcus epidermidis
- With your inoculation loop, draw a small amount of each culture to the middle of the slide and mix.
- Gram stain using the procedure above. Treat all parts of the slide the same.
- Find the cells under oil immersion. As always, you will need to start with the scanning objective. Follow the steps described in Microscope Theory.
- Evaluate your Gram staining technique by locating both rods and cocci. Determine if each is the correct color. Make sure that you are not just looking for both colors. You need to make sure that the rods are pink/red and the cocci are dark purple. Consult with your instructor. Note that on high power (high dry), the resolution is not good enough to determine the cell morphology and color. You must find cells under oil immersion to determine these characteristics.
- If your staining technique is good, your instructor will initial your Data and Observations table and you can then go on to record your observations. Use one row of the table for E. coli and the next line to make observations for the S. epidermidis . Remember, the first time you write the organism name, write it out in full scientific form.
- Dispose of your slide in the sharps container.


1.6: Free Body Diagrams
A free body diagram is a tool used to solve engineering mechanics problems. As the name suggests, the purpose of the diagram is to "free" the body from all other objects and surfaces around it so that it can be studied in isolation. We will also draw in any forces or moments acting on the body, including those forces and moments exerted by the surrounding bodies and surfaces that we removed.
The diagram below shows a ladder supporting a person and the free body diagram of that ladder. As you can see, the ladder is separated from all other objects and all forces acting on the ladder are drawn in with the key dimensions and angles shown.
Constructing the Free Body Diagram:
The first step in solving most mechanics problems will be to construct a free body diagram. This simplified diagram will allow us to more easily write out the equilibrium equations for statics or strengths of materials problems, or the equations of motion for dynamics problems.
To construct the diagram we will use the following process:
- First draw the body being analyzed, separated from all other surrounding bodies and surfaces. Pay close attention to the boundary, identifying what is part of the body, and what is part of the surroundings.
- Second, draw in all external forces and moments acting directly on the body. Do not include any forces or moments that do not directly act on the body being analyzed. Do not include any forces that are internal to the body being analyzed.
- Once the forces are identified and added to the free body diagram, the last step is to label any key dimensions and angles on the diagram.
Some common types of forces seen in mechanics problems are:
- Gravitational Forces: Unless otherwise noted, the mass of an object will result in a gravitational weight force applied to that body. This weight is usually given in pounds in the English system, and is modeled as 9.81 (\(g\)) times the mass of the body in kilograms for the metric system (resulting in a weight in Newtons). This force will always point down towards the center of the earth and act on the center of mass of the body.
-
Normal Forces (or Reaction Forces):
Every object in direct contact with the body will exert a normal force on that body which prevents the two objects from occupying the same space at the same time. Note that only objects in direct contact can exert normal forces on the body.
- An object in contact with another object or surface will experience a normal force that is perpendicular (normal) to the surfaces in contact.
- Joints or connections between bodies can also cause reaction forces or moments, and we will have one force or moment for each type of motion or rotation the connection prevents.
-
Friction Forces:
Objects in direct contact with the body can also exert friction forces, which will resist the two bodies sliding against one another, on the body. These forces will always be perpendicular to the surfaces in contact. Friction is the subject of an entire chapter in this book, but for simple scenarios we usually assume rough or smooth surfaces.
- For smooth surfaces we assume that there is no friction force.
- For rough surfaces we assume that the bodies will not slide relative to one another, no matter what. In this case, the friction force is always just large enough to prevent this sliding.
- Tension in Cables: Cables, wires or ropes attached to the body will exert a tension force on the body in the direction of the cable. These forces will always pull on the body, as ropes, cables and other flexible tethers cannot be used for pushing.
The above forces are the most common, but other forces such as pressure from fluids, spring forces and magnetic forces exist and may act on the body.
Worked Problems:
The drawing below shows two boxes sitting on a table. Draw a free body diagram of box A and box B.
- Solution
Two equally sized barrels are being transported in a handtruck as shown below. Draw a free body diagram of each of the two barrels.
- Solution
The car shown below is moving and then slams on the brakes locking up all four wheels. The distance between the two wheels is 8 feet and the center of mass is 3 feet behind and 2.5 feet above the point of contact between the front wheel and the ground. Draw a free body diagram of the car as it comes to a stop.
- Solution
A 600-pound load is supported by a 5 meter long, 100-pound cantilever beam. Assume the beam is firmly anchored to the wall. Draw a free body diagram of the beam.
- Solution
The main arm of a crane has a mass of 400 kg (assume the center of mass is at the midpoint of the arm), and supports a 200 kg load and a 600 kg counterweight. The arm is connected to the vertical support via a pin joint and two flexible cables. Draw a free body diagram of the arm.
- Solution


1.3: Practicing the Discipline of Workforce Planning
Workforce Planning
Overview
Workforce planning is the process an organization uses to analyze its workforce and determine the steps it must take to prepare for future staffing needs.
Any business plan deals with resource requirements, and, just as financial requirements need to be addressed, the business plan needs to ensure that the appropriate workforce mix is available to accomplish plan goals and objectives. In workforce planning, an organization conducts a systematic assessment of workforce content and composition issues and determines what actions must be taken to respond to future needs. The actions to be taken may depend on external factors (e.g., skill availability) as well as internal factors (e.g., age of the workforce). These factors may determine whether future skill needs will be met by recruiting, by training or by outsourcing the work.
Whether handled separately or as part of the business plan, workforce planning involves working through four issues:
- The composition and content of the workforce that will be required to strategically position the organization to deal with its possible futures and business objectives.
- The gaps that exist between the future "model" organization(s) and the existing organization, including any special skills required by possible futures.
- The recruiting and training plans for permanent and contingent staff that must be put in place to deal with those gaps.
- The determination of the outside sources that will be able to meet the skill needs for functions or processes that are to be outsourced.
While many see workforce planning as purely a staffing tool for anticipating employment needs, it can also be a critical tool for staff training and development and succession planning. To be successful, organizations should conduct a regular and thorough workforce planning assessment so that staffing needs can be measured, training and development goals can be established, and contingent workforce options can be used to create an optimally staffed and trained workforce able to respond to the needs of the business.
Roles of HR and Senior Management in Workforce Planning
Often, a workforce plan is completed simultaneously with organizational strategic planning and is updated with the same frequency as the strategic plan. While the HR department is typically responsible for the bulk of workforce planning initiatives, other members of senior management may be involved in the workforce planning process, including the CEO, COO, CFO and other leaders responsible for organizational strategy. To ensure the effectiveness of a workforce plan, leaders should evaluate the ability of the plan to anticipate and respond to future needs so that the organization can make and execute sound business decisions. Performance indicators will include standard organizational performance measures: profitability, ROI, productivity and so on. An effective performance management system can have a positive impact on the performance indicators of the organization. Benchmarks may also be established by relying on industry data.
Tips for Effective Workforce Planning
For the workforce planning process to be successful, human resource professionals responsible for leading workforce planning initiatives should make sure to:
- Designate a specific member of the HR team to manage the process.
- Find a high-level executive to champion the plan.
- Involve key stakeholders in the workforce planning process.
- Align the plan with the company's strategic business plan.
- Coordinate the workforce plan with succession planning and career development initiatives.
- Make workforce planning an ongoing activity, with continuous evaluation of changes in the internal and external environment that may affect the organization's staffing needs.
Steps in the Workforce Planning Process
Several distinct analytical steps need to be taken in workforce planning:
1. The supply analysis, also referred to as the "supply model" or "staffing assessment," involves an analysis of an organization's current labor supply.
2. The demand analysis, also referred to as the "demand model," includes a review of future business plans and objectives.
3. The gap analysis compares the differences in the supply and demand models and identifies skill surpluses and deficiencies.
4. The solution analysis focuses on how to address gaps in current staffing and future staffing needs through recruiting, training and development, contingent staffing, and outsourcing.
Step 1: Supply analysis
The purpose of the supply model is to analyze the organization as it currently exists—in other words, the supply of labor and skill sets that are vital to an organization. This analysis should encompass not only the number of employees and their skills, but also factors such as workforce demographics and representation of protected classes. Demographics may be especially important in workforce planning if the organization has large numbers of workers nearing retirement age, or if it has large numbers of young workforce entrants with turnover rates exceeding those of older, seasoned employees. Representation of protected classes will have significance for federal or state government contractors, which must comply with applicable affirmative action plan requirements, as well as for organizations that have a voluntary affirmative action plans and that wish to improve representation of underused protected classes.
A supply analysis also involves making projections of attrition (due to resignations, retirements, internal transfers, promotions and involuntary terminations) over the planning horizon being used, so that attrition is taken into account in considering the future supply of labor and skill. From this information, the workforce planner can develop a profile of current staff as it would exist in the future if no action is taken in recruiting, training or outsourcing.
Step 2: Demand analysis
The purpose of the demand model is to forecast the organization's future workforce composition. This forecast should take into consideration a broad range of business issues, including new product lines, competitive forces and expansion/constriction in global marketplaces, anticipated workforce availability within geographic boundaries, and myriad other issues.
Internal and external factors need to be considered in the demand analysis. Analyses of internal demand influences may focus on the following questions, among others:
- Will the current workforce, with minimal retraining, have the skill sets necessary to perform new duties with a new product line?
- Will current employees remain loyal to the organization if it has anticipated changes in mind?
Analyses of external demand influences may consider these questions:
- Is labor readily available that possesses the skills and abilities needed by the evolving organization?
- What external pressures will change demand for goods and services that may ultimately affect internal business decisions and, thus, workforce planning needs?
The future composition of the workforce must also be analyzed. This analysis will seek answers to the following questions:
- How many employees will be necessary to achieve business plan goals and objectives?
- What skills and competencies will be required for the new business?
- What is the composition of the available workforce population?
- What will the organization need to do to attract prospective employees?
- What will the organization need to do to attract and retain a diverse group of workers?
Step 3: Gap analysis
The next step in the process seeks to compare the supply model with the demand model to identify gaps between the composition of the current workforce and future workforce needs. The workforce planning professional may want to categorize a variety of future scenarios and then select the future that is most likely to occur, with contingency planning for alternative futures. When conducting this analysis, the planner should identify the additional number of employees needed who have the requisite skill sets, as well as the employees who will no longer be needed due to limited skill sets.
Step 4: Solution analysis
Solution analysis involves the development of strategies to close the gaps identified in the previous step. Approaches for meeting future workplace demands may include recruiting, training and retraining, using contingent staff, or outsourcing. The approaches selected will be dependent on whether the organization will need to expand, contract, restructure or rely on contingent staff to meet new workplace demands.
Recruiting. When external staff is required to meet a workforce expansion due to demands of new product lines, expanded production or service offerings, or new geographic areas to be served, external recruitment may be the logical strategy to address gaps. Recruiting may also be required as turnover occurs, whether due to employees leaving to find other employment opportunities or to retirement, which may be the case for organizations with large numbers of employees nearing retirement age. Employers can choose among a wide variety of tactics for executing their recruiting strategy. These tactics vary depending on market conditions, the type of targeted candidates, diversity-related issues and other factors. Cost and time are major issues in recruitment. Even if the recruitment process is efficient, it typically costs more and takes longer to find, hire and train a new person than to "recycle" a current employee through internal recruitment. So, in many instances, external recruitment should be the workforce planning strategy of last resort.
Training and retraining. Instead of filling the skills gaps through external recruiting, human resource professionals may choose the less costly solution of employee development, particularly for key high-value positions. Employee development builds on current intellectual capital, retains the corporate culture, and motivates and stimulates the workforce.As skill sets become obsolete due to new technology, new services, additional product lines or other competitive forces, the organization should focus on updating skills and capabilities of their employees as a critical workforce planning strategy. Training, retraining and development may include many methodologies, such as classroom training, on-the-job training, e-learning, webinars and job aids. These activities may concentrate on specific job duties and tasks or on leadership and managerial skills for new leaders.
Contingent staffing. When the current number of employees or their skills sets are insufficient to accomplish the work, given the anticipated business future, contingent staffing may be used to fill that gap. This approach makes sense when the demand model indicates that the numbers of employees will vary significantly and cannot be leveled out through resource allocation strategies. Contingent staffing is often best used when the future is likely to be fluid or highly dynamic; in these circumstances, it may be a better alternative than hiring full-time employees who may not be needed on an ongoing basis. Contingent staffing options include temporary employees, part-time employees, contract workers and consultants. Discussion of each of these types follows.
Temporary workers. Temporary workers may be found internally or externally, depending on the needs of the organization. Although temporary staff is often hired to perform traditional clerical duties, the desire for additional flexibility, as well as early retirement, has resulted in higher-level experienced individuals seeking temporary assignments to meet their personal goals. Today's temporary workers can be hired to work in virtually every level of an organization, including CEOs, controllers, accountants, consultants, IT, marketing and HR.
To maximize the benefits of using temporary workers, human resource professionals should consider whether to use an agency or internal resources, determine selection criteria, ensure successful onboarding, set expectations and effectively manage performance. Organizations will also want to ensure that policies or procedures are established for issues such as screening and selecting temporary agencies, temporary-to-regular employee classification, discipline, work behaviors and legal compliance activities.
Part-time employees. Part-time employees are those who typically work less than a full-time schedule. Many of these employees work a partial day every workday; some work part-week, and some may work part-month. Some may even job-share with another part-time employee. Part-time work can be used to attract diverse workers, including students, parents of young children, older workers and others who need or want to work but do not wish to work a full-time schedule. Most organizations require part-time employees to follow all policies and procedures that their full-time employees must follow. Fewer or different benefits may be offered to part-time employees than to full-time employees.
Contract workers and consultants. Sometimes an organization may need workers who have specialized knowledge or expertise to help meet new business requirements. Independent contractors and consultants may be used to meet these special requirements. Employers should take care in properly identifying contract workers and consultants, as misclassification of these workers can result in violations of the Fair Labor Standards Act or Internal Revenue Service regulations. Classifying a worker as an independent contractor should always be an informed and bona fide business decision, not a subterfuge to avoid the employer's legal obligations to employees. Independent contractor arrangements have drawn increasing scrutiny and significance with the proliferation of workplace laws covering "employees" and the growth of the contingent workforce. Misclassification of an individual as an independent contractor can give rise to a variety of liabilities.
Outsourcing. Organizations may determine that certain non-core business functions would be better accomplished by outsourcing them to an organization that specializes in those functional areas. Jobs that are prime targets for outsourcing are those that require a skill that is critical, in short supply and needed only periodically. If such needs can be handled through contingent staff—for example, by using retirees—the organization will, of course, be ahead. However, many high-demand, low-supply, leading-edge skill needs may be met only through outsourcing to specialized contractors.
To ensure that outsourced functions are properly managed, HR should consider:
- Selecting the right firm.
- Establishing guidelines for a partnering relationship.
- Communication methodologies and protocols.
- Metrics for measuring and ensuring business results.
Succession Planning as a Workforce Planning Tool
Another aspect of effective workforce planning is succession planning. Succession planning is used by organizations to identify and prepare suitable employees to fill key positions when current employees leave their jobs. An effective workforce planning process will include a review of key leadership and business-critical roles and will identify key incumbents able to progress into these roles. Having a succession plan in place generally ensures a smooth continuation of business when key players leave due to retirement, resignations or transfers within the company.
The types of positions included in a succession plan vary by organization. Traditionally, these plans included only executive-level positions. In recent years, however, companies have been selecting successors for positions throughout the organization. During times of economic upheaval, when the economic security of organizations and their staffs may be uncertain, the need for up-to-date succession plans increases. With a wavering economic outlook, downsizing, mergers and acquisitions become more likely. With these events leading to potential increases in turnover, implementing a succession plan is a key strategy an organization can use to reduce turnover costs and ensure smooth transitions. In addition, a succession plan can help foster employee commitment because it demonstrates to employees that the organization supports their development and internal growth.
Organizations use a variety of models for succession planning, which may range from self-identification or nomination to highly sophisticated software tools that maintain information about individual employees' development plans, training and education completed, classes taken, performance evaluations, and recommendations for future development.
Source: Toolkit, Society for Human Resource Management (SHRM), 2024