<IP_ADDRESS>: Flour in Baking
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Flour in Baking
Flour forms the foundation for bread, cakes, and pastries. It may be described as the skeleton, which supports the other ingredients in a baked product. This applies to both yeast and chemically leavened products.
The strength of flour is represented in protein (gluten) quality and quantity. This varies greatly from flour to flour. The quality of the protein indicates the strength and stability of the flour, and the result in bread making depends on the method used to develop the gluten by proper handling during the fermentation. Gluten is a rubber-like substance that is formed by mixing flour with water. Before it is mixed it contains two proteins. In wheat, these two proteins are gliadin and glutenin . Although we use the terms protein and gluten interchangeably, gluten only develops once the flour is moistened and mixed. The protein in the flour becomes gluten.
Hard spring wheat flours are considered the best for bread making as they have a larger percentage of good quality gluten than soft wheat flours. It is not an uncommon practice for mills to blend hard spring wheat with hard winter wheat for the purpose of producing flour that combines the qualities of both. Good bread flour should have about 13% gluten.
Storing Flour
Flour should be kept in a dry, well-ventilated storeroom at a fairly uniform temperature. A temperature of about 70°F with a relative humidity of 60% is considered ideal. Flour should never be stored in a damp place. Moist storerooms with temperatures greater than 74°F are conducive to mold growth, bacterial development, and rapid deterioration of the flour. A well-ventilated storage room is necessary because flour absorbs and retains odors. For this reason, flour should not be stored in the same place as onions, garlic, coffee, or cheese, all of which give off strong odors.
Flour Tests
Wheat that is milled and blended with modern milling methods produces flours that have a fairly uniform quality all year round and, if purchased from a reliable mill, they should not require any testing for quality. The teacher, student, and professional baker, however, should be familiar with qualitative differences in flours and should know the most common testing methods.
Flours are mainly tested for:
- Color
- Absorption
- Gluten strength
- Baking quality
Other tests, done in a laboratory, are done for:
- Albumen
- Starch
- Sugar
- Dextrin
- Mineral and fat content
Color
The color of the flour has a direct bearing on baked bread, providing that fermentation has been carried out properly. The addition of other ingredients to the dough, such as brown sugar , malt, molasses, salt, and colored margarine, also affects the color of the bread.
To test the color of the flour, place a small quantity on a smooth glass, and with a spatula, work until a firm smooth mass about 2 in. square is formed. The thickness should be about 2 cm (4/5 in.) at the back of the plate to a thin film at the front. The test should be made in comparison with a flour of known grade and quality, both flours being worked side by side on the same glass. A creamy white color indicates a hard flour of good gluten quality. A dark or grayish color indicates a poor grade of flour or the presence of dirt. Bran specks indicate a low grade of flour.
After making a color comparison of the dry samples, dip the glass on an angle into clean water and allow to partially dry. Variations in color and the presence of bran specks are more easily identified in the damp samples.
Absorption
Flours are tested for absorption because different flours absorb different amounts of water and therefore make doughs of different consistencies. The absorption ability of a flour is usually between 55% and 65%. To determine the absorption factor, place a small quantity of flour (100 g/4 oz.) in a bowl. Add water gradually from a beaker containing a known amount of water. As the water is added, mix with a spoon until the dough reaches the desired consistency. You can knead the dough by hand for final mixing and determination of consistency. Weigh the unused water. Divide the weight of the water used by the weight of the flour used. The result is the absorption ability in percentage. For example:
Weight of flour used 100 g (4 oz.)
Weight of water used 60 g (2.7 oz.)
Therefore absorption = 6/10 or 60%
Prolonged storage in a dry place results in a natural moisture loss in flour and has a noticeable effect on the dough. For example, a sack of flour that originally weighed 40 kg (88 lb.) with a moisture content of 14% may be reduced to 39 kg (86 lb.) during storage. This means that 1 kg (2 lb.) of water is lost and must be made up when mixing. The moisture content of the wheat used to make the flour is also important from an economic standpoint.
Hard wheat flour absorbs more liquid than soft flour. Good hard wheat flour should feel somewhat granular when rubbed between the thumb and fingers. A soft, smooth feeling indicates soft wheat flour or a blend of soft and hard wheat flour. Another indicator is that hard wheat flour retains its form when pressed in the hollow of the hand and falls apart readily when touched. Soft wheat flour tends to remain lumped together after pressure.
Gluten Strength
The gluten test is done to find the variation of gluten quality and quantity in different kinds of flour. Hard flour has more gluten of better quality than soft flour. The gluten strength and quality of two different kinds of hard flour may also vary with the weather conditions and the place where the wheat is grown. The difference may be measured exactly by laboratory tests, or roughly assessed by the variation of gluten balls made from different kinds of hard flours.
For example, to test the gluten in hard flour and all-purpose flour, mix 9 oz. of each in separate mixing bowls with enough water to make each dough stiff. Mix and develop each dough until smooth. Let the dough rest for about 10 minutes. Wash each dough separately while kneading it under a stream of cold water until the water runs clean and all the starch is washed out. (Keep a flour sieve in the sink to prevent dough pieces from being washed down the drain.) What remains will be crude gluten. Shape the crude gluten into round balls, then place them on a paper-lined baking pan and bake at 420°F for about one hour. The gluten ball made from hard flour will be larger than the one made from all-purpose flour. This illustrates the ability of hard flour to produce a greater volume because of its higher gluten content.
Ash Content
Ash or mineral content of the flour is used as another measurement of quality. Earlier in the chapter, we talked about extraction rates as an indicator of how much of the grain has been refined. Ash content refers to the amount of ash that would be left over if you were to burn 100 g of flour. A higher ash content indicates that the flour contains more of the germ, bran, and outer endosperm. Lower ash content means that the flour is more highly refined (i.e., a lower extraction rate).
Baking Quality
The final and conclusive test of any flour is the kind of bread that can be made from it. The baking test enables the baker to check on the completed loaf that can be expected from any given flour. Good volume is related to good quality gluten; poor volume to young or green flour. Flour that lacks stability or power to hold during the entire fermentation may result in small, flatbread. Flour of this type may sometimes respond to an increase in the amount of yeast. More yeast shortens the fermentation time and keeps the dough in better condition during the pan fermentation period.


13.3B: The Vestibular System
Gravity, acceleration, and deceleration are detected by evaluating the inertia on receptive cells in the vestibular system.
- Identify the structures of the vestibular system that respond to gravity
Key Points
- The vestibular system uses hair cells, as does the auditory system, but it excites them in different ways.
- There are five vestibular receptor organs in the inner ear (the vestibular labyrinth): the utricle, the saccule, and three semicircular canals; the utricle and saccule respond to acceleration in a straight line, such as gravity.
- The bending of the stereocilia stimulates specific neurons that signal to the brain that the head is tilted, allowing the maintenance of balance.
- The fluid-filled semicircular canals are tubular loops set at oblique angle, arranged in three spatial planes; the base of each canal contains a cluster of hair cells that monitor angular acceleration and deceleration from rotation.
- Neuronal projections to the temporal cortex account for feelings of dizziness; projections to autonomic nervous system areas in the brainstem account for motion sickness; and projections to the primary somatosensory cortex monitor subjective measurements of the external world and self-movement.
Key Terms
- vestibulocochlear : of or pertaining to the vestibular and cochlear nerves
- vestibular system : the sensory system in mammals that contributes to movement, sense of balance, and spatial orientation
- stereocilium : any of many nonmotile cellular structures resembling long microvilli; those of the inner ear are responsible for auditory transduction
Vestibular Information
The stimuli associated with the vestibular system are linear acceleration (gravity) and angular acceleration/deceleration. Gravity, acceleration, and deceleration are detected by evaluating the inertia on receptive cells in the vestibular system. Gravity is detected through head position, while angular acceleration and deceleration are expressed through turning or tilting of the head.
The vestibular system has some similarities with the auditory system. It utilizes hair cells just like the auditory system, but it excites them in different ways. There are five vestibular receptor organs in the inner ear, all of which help to maintain balance: the utricle, the saccule, and three semicircular canals. Together, they make up what is known as the vestibular labyrinth. The utricle and saccule are most responsive to acceleration in a straight line, such as gravity. The roughly 30,000 hair cells in the utricle and 16,000 hair cells in the saccule lie below a gelatinous layer, with their stereocilia (singular: stereocilium) projecting into the gelatin. Embedded in this gelatin are calcium carbonate crystals, similar to tiny rocks. When the head is tilted, the crystals continue to be pulled straight down by gravity, but the new angle of the head causes the gelatin to shift, thereby bending the stereocilia. The bending of the stereocilia stimulates specific neurons that signal to the brain that the head is tilted, allowing the maintenance of balance. It is the vestibular branch of the vestibulocochlear cranial nerve that deals with balance.
Vestibular labrynth : The structure of the vestibular labyrinth is made up of five vestibular receptor organs in the inner ear: the utricle, the saccule, and three semicircular canals.
The fluid-filled semicircular canals are tubular loops set at oblique angles, arranged in three spatial planes. The base of each canal has a swelling that contains a cluster of hair cells. The hairs project into a gelatinous cap, the cupula, where they monitor angular acceleration and deceleration from rotation. They would be stimulated by driving your car around a corner, turning your head, or falling forward. One canal lies horizontally, while the other two lie at about 45 degree angles to the horizontal axis. When the brain processes input from all three canals together, it can detect angular acceleration or deceleration in three dimensions. When the head turns, the fluid in the canals shifts, thereby bending stereocilia and sending signals to the brain. Upon cessation of acceleration or deceleration, the movement of the fluid within the canals slows or stops. For example, imagine holding a glass of water. When moving forward, water may splash backwards onto the hand; when motion has stopped, water may splash forward onto the fingers. While in motion, the water settles in the glass and does not splash. Note that the canals are not sensitive to velocity itself, but to changes in velocity. In this way, moving forward at 60 mph with your eyes closed would not give the sensation of movement, but suddenly accelerating or braking would stimulate the receptors.
Higher Processing
Hair cells from the utricle, saccule, and semicircular canals also communicate through bipolar neurons to the cochlear nucleus in the medulla. Cochlear neurons send descending projections to the spinal cord and ascending projections to the pons, thalamus, and cerebellum. Connections to the cerebellum are important for coordinated movements. There are also projections to the temporal cortex, which account for feelings of dizziness; projections to autonomic nervous system areas in the brainstem, which account for motion sickness; and projections to the primary somatosensory cortex, which monitors subjective measurements of the external world and self-movement. People with lesions in the vestibular area of the somatosensory cortex see vertical objects in the world as being tilted. Finally, the vestibular signals project to certain optic muscles to coordinate eye and head movements.


9.2.5: Double-Edged Pen
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In a country whose middle name is independence, where do we really see the mark of an individual? We are surrounded by a conflicting culture that is trying to do its own thing while simultaneously trying to fit in. Ralph Waldo Emerson’s Self-Reliance demonstrates this paradox. He spends a majority of the text arguing in favor of nonconformity and originality, but Emerson contradicts his own definition of individuality by writing this essay.
Emerson is telling us how to not conform. By telling us how to do anything, he is encouraging us to conform to his word. “Your isolation must not be mechanical, but spiritual,” (13). It must, must it? He writes that “it demands something godlike in him who has cast off the common motives of humanity and has ventured to trust himself for a taskmaster,” (14). But if Emerson were reading this, how would he react to being told he “must” do anything? He writes that “it is only as a man puts off all foreign support, and stands alone, that I see him to be strong and to prevail,” (21). Emerson would respect someone who is being an individual, but if someone was choosing to do that based on reading this essay, we would not be able to refer to them as an individual. They acted upon media they took in, and not from their own instinct or spontaneity.
Let us also consider that Emerson is relating our “selves” to the hand of God, and saying that when we act on our instinct, that is us listening to our internal voice of God. “The soul, is not diverse from things, from space, from light, from time, from man, but one with them,” (10). Here is an essay where he is arguing that we all have our individual interests and motives, he states that we are actually all part of one whole. He is telling us to make ourselves separate from the wholeness of society, but we should accept the fact that we are part of one bigger whole, that is bigger than society. “All men have my blood, and I have all men’s,” he states, so doesn’t that mean that we all inherently share a part of ourselves (!3)? How can he then say that “[e]very man is unique,” (18)?
Emerson explicitly argues that in order to achieve transcendental individuality, one can not imitate because “…imitation is suicide;…’(2). However, he also explicitly advocates for the greatness of those before him. “Pythagoras was misunderstood, and Socrates, and Jesus, and Luther, and Copernicus, and Galileo, and Newton, and every pure and wise spirit that ever took flesh. To be great is to be understood.”(7) If the intention that Emerson embedded in this essay was to inform readers on how to be individual, he has failed. Not only has he failed to give a clear-minded guide to originality, but he has also contradicted himself. Later on, on page 8, he goes back on his praise of Jesus. “Christ is born, and millions of minds so grow and cleave to his genius, that he is confounded with virtue and the possible of man. An institution is the lengthened shadow of one man;…”(8).
Emerson argues that “truth is handsomer than the affection of love” (4). However, his use of the word “handsome” creates some holes in his statement. Sure, love and affection may not have nice appearances, but one can still be kind and affectionate as an individual. He says “…do not expect me, as a good man did to-day, of my obligation to put all poor men in good situations. Are they my poor… I give to such men as do not belong to me and to whom I do not belong.” His implication that charity is conformity is somewhat undermined by the use of such a subjective word. In this instance, he uses an implicit piece of evidence and still manages to contradict himself in some way.
In Emerson’s ideal society, every member would be an individual that only acted upon their internal instinct. This type of culture, however, would not allow for the sharing of ideas, the forming of social bonds, or the formation of a community that shares ideas and interest. Without the ability to collaborate, our current society would not be able to exist. Self – Reliance is a text that questions the relationship between the members of a society. America values the profit that is a result of this collaboration. Therefore, how American is Emerson? By contradicting his definitions of originality and individualism, he is relinquishing his Americanness.


8.2: Ionic Bonding
- Explain the formation of cations, anions, and ionic compounds
- Predict the charge of common metallic and nonmetallic elements, and write their electron configurations
As you have learned, ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell.
Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds : electrostatic forces of attraction between oppositely charged cations and anions. The properties of ionic compounds shed some light on the nature of ionic bonds. Ionic solids exhibit a crystalline structure and tend to be rigid and brittle; they also tend to have high melting and boiling points, which suggests that ionic bonds are very strong. Ionic solids are also poor conductors of electricity for the same reason—the strength of ionic bonds prevents ions from moving freely in the solid state. Most ionic solids, however, dissolve readily in water. Once dissolved or melted, ionic compounds are excellent conductors of electricity and heat because the ions can move about freely.
Neutral atoms and their associated ions have very different physical and chemical properties. Sodium atoms form sodium metal, a soft, silvery-white metal that burns vigorously in air and reacts explosively with water. Chlorine atoms form chlorine gas, Cl 2 , a yellow-green gas that is extremely corrosive to most metals and very poisonous to animals and plants. The vigorous reaction between the elements sodium and chlorine forms the white, crystalline compound sodium chloride, common table salt, which contains sodium cations and chloride anions (Figure Figure \(\PageIndex{1}\)). The compound composed of these ions exhibits properties entirely different from the properties of the elements sodium and chlorine. Chlorine is poisonous, but sodium chloride is essential to life; sodium atoms react vigorously with water, but sodium chloride simply dissolves in water.
The Formation of Ionic Compounds
Binary ionic compounds are composed of just two elements: a metal (which forms the cations) and a nonmetal (which forms the anions). For example, NaCl is a binary ionic compound. We can think about the formation of such compounds in terms of the periodic properties of the elements. Many metallic elements have relatively low ionization potentials and lose electrons easily. These elements lie to the left in a period or near the bottom of a group on the periodic table. Nonmetal atoms have relatively high electron affinities and thus readily gain electrons lost by metal atoms, thereby filling their valence shells. Nonmetallic elements are found in the upper-right corner of the periodic table.
As all substances must be electrically neutral, the total number of positive charges on the cations of an ionic compound must equal the total number of negative charges on its anions. The formula of an ionic compound represents the simplest ratio of the numbers of ions necessary to give identical numbers of positive and negative charges. For example, the formula for aluminum oxide, Al 2 O 3 , indicates that this ionic compound contains two aluminum cations, Al 3 + , for every three oxide anions, O 2− [thus, (2 × +3) + (3 × –2) = 0].
It is important to note, however, that the formula for an ionic compound does not represent the physical arrangement of its ions. It is incorrect to refer to a sodium chloride (NaCl) “molecule” because there is not a single ionic bond, per se, between any specific pair of sodium and chloride ions. The attractive forces between ions are isotropic—the same in all directions—meaning that any particular ion is equally attracted to all of the nearby ions of opposite charge. This results in the ions arranging themselves into a tightly bound, three-dimensional lattice structure. Sodium chloride, for example, consists of a regular arrangement of equal numbers of Na + cations and Cl – anions (Figure Figure \(\PageIndex{2}\)).
The strong electrostatic attraction between Na + and Cl – ions holds them tightly together in solid NaCl. It requires 769 kJ of energy to dissociate one mole of solid NaCl into separate gaseous Na + and Cl – ions:
\[\ce{NaCl}(s)⟶\ce{Na+}(g)+\ce{Cl-}(g)\hspace{20px}ΔH=\mathrm{769\:kJ} \nonumber \]
Electronic Structures of Cations
When forming a cation, an atom of a main group element tends to lose all of its valence electrons, thus assuming the electronic structure of the noble gas that precedes it in the periodic table. For groups 1 (the alkali metals) and 2 (the alkaline earth metals), the group numbers are equal to the numbers of valence shell electrons and, consequently, to the charges of the cations formed from atoms of these elements when all valence shell electrons are removed. For example, calcium is a group 2 element whose neutral atoms have 20 electrons and a ground state electron configuration of 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 . When a Ca atom loses both of its valence electrons, the result is a cation with 18 electrons, a 2+ charge, and an electron configuration of 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 . The Ca 2 + ion is therefore isoelectronic with the noble gas Ar.
Potassium is required in our diet. Write the electron configuration for a potassium ion.
Solution
First, write the electron configuration for the neutral atom:
- K: [Ar]4 s 1
Next, remove electrons from the highest energy orbital. Potassium is a member of group 1, so it should have a charge of 1+, and thus loses one electron from its s orbital. This gives the following electron configuration for the ion:
- K 2 + : [Ar]
Magnesium is also required in our diet. Write the electron configurations of the ion.
- Answer
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Mg 2 + : [Ne]
Electronic Structures of Anions
Most monatomic anions form when a neutral nonmetal atom gains enough electrons to completely fill its outer s and p orbitals, thereby reaching the electron configuration of the next noble gas. Thus, it is simple to determine the charge on such a negative ion: The charge is equal to the number of electrons that must be gained to fill the s and p orbitals of the parent atom. Oxygen, for example, has the electron configuration 1 s 2 2 s 2 2 p 4 , whereas the oxygen anion has the electron configuration of the noble gas neon (Ne), 1 s 2 2 s 2 2 p 6 . The two additional electrons required to fill the valence orbitals give the oxide ion the charge of 2– (O 2– ).
Selenium and iodine are two essential trace elements that form anions. Write the electron configurations of the anions.
Solution
Se 2 – : [Ar]3 d 10 4 s 2 4 p 6
I – : [Kr]4 d 10 5 s 2 5 p 6
Write the electron configurations of a phosphorus atom and its negative ion. Give the charge on the anion.
- Answer
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P: [Ne]3 s 2 3 p 3
P 3– : [Ne]3 s 2 3 p 6
Summary
Atoms gain or lose electrons to form ions with particularly stable electron configurations. The charges of cations formed by the representative metals may be determined readily because, with few exceptions, the electronic structures of these ions have either a noble gas configuration or a completely filled electron shell. The charges of anions formed by the nonmetals may also be readily determined because these ions form when nonmetal atoms gain enough electrons to fill their valence shells.
Glossary
- inert pair effect
- tendency of heavy atoms to form ions in which their valence s electrons are not lost
- ionic bond
- strong electrostatic force of attraction between cations and anions in an ionic compound


7.4: Brainstorming Related Terms
Describing Main Concepts
In many instances, there are various ways that a main concept can be described. Not every information source will use the same term to describe the same thing! Take the topic of genetically modified food, for example. Though “genetically modified food” is commonly used, terms like “GMO,” “genetically modified organism,” “genetic engineering,” and “genetic modification” are often used by scientists to describe the same thing.
This is also a good time to look at your main concepts and decide if the keywords you’ve selected to describe them are too broad or too narrow. In the previous example, using the key phrase genetic engineering when looking for information about specific types of organisms that have been genetically modified, may be too broad of a term that yields irrelevant results. Also keep in mind the type of information you are searching for: If you need scholarly research articles, scientific terminology is more likely to be used in those resources; if you are searching for information that may appear in popular periodicals (like magazines and newspapers), more general, everyday language is likely to be used (e.g., myocardial infarction versus heart attack).
Brainstorming Alternatives
It can be helpful to list your keywords and any alternative or related keywords or phrases that may be helpful to your search. You may want to return to those reference sources you used for finding background information on your topic to see what terms and phrases were used. You may also try searching in a thesaurus for some synonyms, and you may even come back to this step later in the research process once you have completed some initial searches and discovered some helpful new alternative terms. Some databases will also list “related terms,” which can be helpful for modifying your search. On the other hand, some keywords are unique, and have no other terms that could be used in their place.
| Main Concept/ Keyword | Alternative/Related | Alternative/Related | Alternative/Related |
|---|---|---|---|
| divorce | separation | split up | parental conflict |
| student’s GPA | grade point average | academic performance | academic achievement |
| high school | school | secondary school | — |


17.3: Cellular Defenses
- Identify and describe the components of blood
- Explain the process by which the formed elements of blood are formed (hematopoiesis)
- Describe the characteristics of formed elements found in peripheral blood, as well as their respective functions within the innate immune system
In the previous section, we discussed some of the chemical mediators found in plasma, the fluid portion of blood. The nonfluid portion of blood consists of various types of formed elements, so called because they are all formed from the same stem cells found in bone marrow. The three major categories of formed elements are: red blood cells (RBCs), also called erythrocytes; platelets, also called thrombocytes; and white blood cells (WBCs), also called leukocytes.
Red blood cells are primarily responsible for carrying oxygen to tissues. Platelets are cellular fragments that participate in blood clot formation and tissue repair. Several different types of WBCs participate in various nonspecific mechanisms of innate and adaptive immunity. In this section, we will focus primarily on the innate mechanisms of various types of WBCs.
Hematopoiesis
All of the formed elements of blood are derived from pluripotent hematopoietic stem cells (HSCs) in the bone marrow. As the HSCs make copies of themselves in the bone marrow, individual cells receive different cues from the body that control how they develop and mature. As a result, the HSCs differentiate into different types of blood cells that, once mature, circulate in peripheral blood. This process of differentiation, called hematopoiesis, is shown in more detail in Figure \(\PageIndex{1}\).
In terms of sheer numbers, the vast majority of HSCs become erythrocytes. Much smaller numbers become leukocytes and platelets. Leukocytes can be further subdivided into granulocytes, which are characterized by numerous granules visible in the cytoplasm, and agranulocytes, which lack granules. Figure \(\PageIndex{2}\) provides an overview of the various types of formed elements, including their relative numbers, primary function, and lifespans.
Granulocytes
The various types of granulocytes can be distinguished from one another in a blood smear by the appearance of their nuclei and the contents of their granules, which confer different traits, functions, and staining properties. The neutrophils, also called polymorphonuclear neutrophils (PMNs), have a nucleus with three to five lobes and small, numerous, lilac-colored granules. Each lobe of the nucleus is connected by a thin strand of material to the other lobes. The eosinophils have fewer lobes in the nucleus (typically 2–3) and larger granules that stain reddish-orange. The basophils have a two-lobed nucleus and large granules that stain dark blue or purple (Figure \(\PageIndex{3}\)).
Neutrophils (PMNs)
Neutrophils (PMNs) are frequently involved in the elimination and destruction of extracellular bacteria. They are capable of migrating through the walls of blood vessels to areas of bacterial infection and tissue damage, where they seek out and kill infectious bacteria. PMN granules contain a variety of defensins and hydrolytic enzymes that help them destroy bacteria through phagocytosis (described in more detail in Pathogen Recognition and Phagocytosis ) In addition, when many neutrophils are brought into an infected area, they can be stimulated to release toxic molecules into the surrounding tissue to better clear infectious agents. This is called degranulation.
Another mechanism used by neutrophils is neutrophil extracellular traps (NETs), which are extruded meshes of chromatin that are closely associated with antimicrobial granule proteins and components. Chromatin is DNA with associated proteins (usually histone proteins, around which DNA wraps for organization and packing within a cell). By creating and releasing a mesh or lattice-like structure of chromatin that is coupled with antimicrobial proteins, the neutrophils can mount a highly concentrated and efficient attack against nearby pathogens. Proteins frequently associated with NETs include lactoferrin, gelatinase, cathepsin G, and myeloperoxidase. Each has a different means of promoting antimicrobial activity, helping neutrophils eliminate pathogens. The toxic proteins in NETs may kill some of the body’s own cells along with invading pathogens. However, this collateral damage can be repaired after the danger of the infection has been eliminated.
As neutrophils fight an infection, a visible accumulation of leukocytes, cellular debris, and bacteria at the site of infection can be observed. This buildup is what we call pus (also known as purulent or suppurative discharge or drainage). The presence of pus is a sign that the immune defenses have been activated against an infection; historically, some physicians believed that inducing pus formation could actually promote the healing of wounds. The practice of promoting “laudable pus” (by, for instance, wrapping a wound in greasy wool soaked in wine) dates back to the ancient physician Galen in the 2nd century AD, and was practiced in variant forms until the 17th century (though it was not universally accepted). Today, this method is no longer practiced because we now know that it is not effective. Although a small amount of pus formation can indicate a strong immune response, artificially inducing pus formation does not promote recovery.
Eosinophils
Eosinophils are granulocytes that protect against protozoa and helminths; they also play a role in allergic reactions. The granules of eosinophils, which readily absorb the acidic reddish dye eosin, contain histamine, degradative enzymes, and a compound known as major basic protein (MBP) (Figure \(\PageIndex{3}\)). MBP binds to the surface carbohydrates of parasites, and this binding is associated with disruption of the cell membrane and membrane permeability.
Basophils
Basophils have cytoplasmic granules of varied size and are named for their granules’ ability to absorb the basic dye methylene blue (Figure \(\PageIndex{3}\)). Their stimulation and degranulation can result from multiple triggering events. Activated complement fragments C3a and C5a, produced in the activation cascades of complement proteins, act as anaphylatoxins by inducing degranulation of basophils and inflammatory responses. This cell type is important in allergic reactions and other responses that involve inflammation. One of the most abundant components of basophil granules is histamine, which is released along with other chemical factors when the basophil is stimulated. These chemicals can be chemotactic and can help to open the gaps between cells in the blood vessels. Other mechanisms for basophil triggering require the assistance of antibodies, as discussed in B Lymphocytes and Humoral Immunity .
Mast Cells
Hematopoiesis also gives rise to mast cells, which appear to be derived from the same common myeloid progenitor cell as neutrophils, eosinophils, and basophils. Functionally, mast cells are very similar to basophils, containing many of the same components in their granules (e.g., histamine) and playing a similar role in allergic responses and other inflammatory reactions. However, unlike basophils, mast cells leave the circulating blood and are most frequently found residing in tissues. They are often associated with blood vessels and nerves or found close to surfaces that interface with the external environment, such as the skin and mucous membranes in various regions of the body (Figure \(\PageIndex{4}\)).
- Describe the granules and nuclei of neutrophils, eosinophils, basophils, and mast cells.
- Name three antimicrobial mechanisms of neutrophils
Angela’s tests come back negative for all common allergens, and her sputum samples contain no abnormal presence of pathogenic microbes or elevated levels of members of the normal respiratory microbiota. She does, however, have elevated levels of inflammatory cytokines in her blood.
The swelling of her airway has still not responded to treatment with antihistamines or corticosteroids. Additional blood work shows that Angela has a mildly elevated white blood cell count but normal antibody levels. Also, she has a lower-than-normal level of the complement protein C4.
- What does this new information reveal about the cause of Angela’s constricted airways?
- What are some possible conditions that could lead to low levels of complement proteins?
Agranulocytes
As their name suggests, agranulocytes lack visible granules in the cytoplasm. Agranulocytes can be categorized as lymphocytes or monocytes (Figure \(\PageIndex{2}\)). Among the lymphocytes are natural killer cells, which play an important role in nonspecific innate immune defenses. Lymphocytes also include the B cells and T cells, which are discussed in the next chapter because they are central players in the specific adaptive immune defenses. The monocytes differentiate into macrophages and dendritic cells, which are collectively referred to as the mononuclear phagocyte system.
Natural Killer Cells
Most lymphocytes are primarily involved in the specific adaptive immune response, and thus will be discussed in the following chapter. An exception is the natural killer cells (NK cells); these mononuclear lymphocytes use nonspecific mechanisms to recognize and destroy cells that are abnormal in some way. Cancer cells and cells infected with viruses are two examples of cellular abnormalities that are targeted by NK cells. Recognition of such cells involves a complex process of identifying inhibitory and activating molecular markers on the surface of the target cell. Molecular markers that make up the major histocompatibility complex (MHC) are expressed by healthy cells as an indication of “self.” This will be covered in more detail in next chapter. NK cells are able to recognize normal MHC markers on the surface of healthy cells, and these MHC markers serve as an inhibitory signal preventing NK cell activation. However, cancer cells and virus-infected cells actively diminish or eliminate expression of MHC markers on their surface. When these MHC markers are diminished or absent, the NK cell interprets this as an abnormality and a cell in distress. This is one part of the NK cell activation process (Figure \(\PageIndex{5}\)). NK cells are also activated by binding to activating molecular molecules on the target cell. These activating molecular molecules include “altered self” or “nonself” molecules. When a NK cell recognizes a decrease in inhibitory normal MHC molecules and an increase in activating molecules on the surface of a cell, the NK cell will be activated to eliminate the cell in distress.
Once a cell has been recognized as a target, the NK cell can use several different mechanisms to kill its target. For example, it may express cytotoxic membrane proteins and cytokines that stimulate the target cell to undergo apoptosis, or controlled cell suicide. NK cells may also use perforin-mediated cytotoxicity to induce apoptosis in target cells. This mechanism relies on two toxins released from granules in the cytoplasm of the NK cell: perforin, a protein that creates pores in the target cell, and granzymes, proteases that enter through the pores into the target cell’s cytoplasm, where they trigger a cascade of protein activation that leads to apoptosis. The NK cell binds to the abnormal target cell, releases its destructive payload, and detaches from the target cell. While the target cell undergoes apoptosis, the NK cell synthesizes more perforin and proteases to use on its next target.
NK cells contain these toxic compounds in granules in their cytoplasm. When stained, the granules are azurophilic and can be visualized under a light microscope (Figure \(\PageIndex{6}\)). Even though they have granules, NK cells are not considered granulocytes because their granules are far less numerous than those found in true granulocytes. Furthermore, NK cells have a different lineage than granulocytes, arising from lymphoid rather than myeloid stem cells (Figure \(\PageIndex{1}\)).
Monocytes
The largest of the white blood cells, monocytes have a nucleus that lacks lobes, and they also lack granules in the cytoplasm (Figure \(\PageIndex{7}\)). Nevertheless, they are effective phagocytes, engulfing pathogens and apoptotic cells to help fight infection.
When monocytes leave the bloodstream and enter a specific body tissue, they differentiate into tissue-specific phagocytes called macrophages and dendritic cells. They are particularly important residents of lymphoid tissue, as well as nonlymphoid sites and organs. Macrophages and dendritic cells can reside in body tissues for significant lengths of time. Macrophages in specific body tissues develop characteristics suited to the particular tissue. Not only do they provide immune protection for the tissue in which they reside but they also support normal function of their neighboring tissue cells through the production of cytokines. Macrophages are given tissue-specific names, and a few examples of tissue-specific macrophages are listed in Table \(\PageIndex{1}\). Dendritic cells are important sentinels residing in the skin and mucous membranes, which are portals of entry for many pathogens. Monocytes, macrophages, and dendritic cells are all highly phagocytic and important promoters of the immune response through their production and release of cytokines. These cells provide an essential bridge between innate and adaptive immune responses, as discussed in the next section as well as the next chapter.
| Tissue | Macrophage |
|---|---|
| Brain and central nervous system | Microglial cells |
| Liver | Kupffer cells |
| Lungs | Alveolar macrophages (dust cells) |
| Peritoneal cavity | Peritoneal macrophages |
- Describe the signals that activate natural killer cells.
- What is the difference between monocytes and macrophages?
Key Concepts and Summary
- The formed elements of the blood include red blood cells ( erythrocytes ), white blood cells ( leukocytes ), and platelets (thrombocytes ). Of these, leukocytes are primarily involved in the immune response.
- All formed elements originate in the bone marrow as stem cells (HSCs) that differentiate through hematopoiesis .
- Granulocytes are leukocytes characterized by a lobed nucleus and granules in the cytoplasm. These include neutrophils (PMNs) , eosinophils , and basophils .
- Neutrophils are the leukocytes found in the largest numbers in the bloodstream and they primarily fight bacterial infections.
- Eosinophils target parasitic infections. Eosinophils and basophils are involved in allergic reactions. Both release histamine and other proinflammatory compounds from their granules upon stimulation.
- Mast cells function similarly to basophils but can be found in tissues outside the bloodstream.
- Natural killer ( NK ) cells are lymphocytes that recognize and kill abnormal or infected cells by releasing proteins that trigger apoptosis.
- Monocytes are large, mononuclear leukocytes that circulate in the bloodstream. They may leave the bloodstream and take up residence in body tissues, where they differentiate and become tissue-specific macrophages and dendritic cells .


8.4: Discrete Methods - Sealed Bids and Markers
There are two more fair division methods that deal with discrete objects. It two heirs have to split a house they cannot just cut the house in half. Instead we have to figure out a way to keep the house intact and still have both heirs feel like they received a fair share. The method of sealed bids is used for dividing up a small number of objects not necessarily similar in value. If there are many objects similar in value, like a jewelry collection, the method of markers can be used to find a fair division.
Method of Sealed Bids
The method of sealed bids can be used to split up an estate among a small number of heirs. A nice feature of this method is that every player in the game ends up with more than a fair share (in their own eyes). The method can also be used when business partners wish to dissolve a partnership in an equitable way or roommates want to divide up a large list of chores.
We make the following assumptions in the method of sealed bids.
- The players are the only ones involved in the game and are willing to accept the outcome.
- The players have no prior knowledge of the other players’ preferences so they do not try to manipulate the game. If this assumption is not met the game might not produce a fair division.
- The players are not emotionally/irrationally attached to any of the items. The players will settle for any of the items or cash as long as it is a fair share. For example, no one would say “I want the house and I will do anything to get it.”
The easiest way to explain the method is to work through an example. An easy way to keep the steps neat and organized is to do the steps in one big table, working from the top to the bottom.
Example \(\PageIndex{1}\): Method of Sealed Bids, #1
Three heirs, Alice, Betty and Charles inherit an estate consisting of a house, a painting and a tractor. They decide to use the method of sealed bids to divide the estate among themselves.
- The players each submit a list of bids for the items. The bid is the value that a player would assign to the item. The bids are done privately and independently. The bids are usually listed in a table.
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
- For each item, the player with the highest bid wins the item. The winning bids are highlighted in the table.
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
- For each player find the sum of his/her bids. This amount is what the player thinks the whole estate is worth. For three players, each player is entitled to one third of the estate. Divide each sum by three to get a fair share for each player. Remember that each player sees the values differently so the fair shares will not be the same.
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
| Total Bids | $411,000 | $405,000 | $435,000 |
| Fair Share | $137,000 | $135,000 | $145,000 |
- Each player either gets more than his/her fair or less than his/her fair share when the items are awarded. Find the difference between the fair share and the items awarded for each player. If a player was awarded more than his/her fair share, the player owes the difference to the estate. If a player was awarded less than his/her fair share, the estate owes the player the difference.
Alice: $137,000 - $75,000 = $62,000. The estate owes Alice $62,000.
Betty: $135,000 - $0 = $135,000. The estate owes Betty $135,000.
Charles: $145,000 – ($300,000 + $63,000) = -$218,000. Charles owes the estate $218,000.
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
| Total Bids | $411,000 | $405,000 | $435,000 |
| Fair Share | $137,000 | $135,000 | $145,000 |
| Owed to Estate | $218,000 | ||
| Estate Owes | $62,000 | $135,000 |
- At this point in the game, there is always some extra money in the estate called the surplus. To find the surplus, we find the difference between all the money owed to the estate and all the money the estate owes.
$218,000 – ($62,000 + $135,000) = $21,000.
Divide this surplus evenly between the three players.
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
| Total Bids | $411,000 | $405,000 | $435,000 |
| Fair Share | $137,000 | $135,000 | $145,000 |
| Owed to Estate | $218,000 | ||
| Estate Owes | $62,000 | $135,000 | |
| Share of Surplus | $7,000 | $7,000 | $7,000 |
- Finish the problem by combining the share of the surplus to either the amount owed to the estate or the amount the estate owes. Include the items awarded in the final share as well as any money.
Alice: $62,000 + $7,000 = $69,000
Betty: $135,000 + $7,000 = $142,000
Charles: -$218,000 + $7,000 = -$211,000
| Alice | Betty | Charles | |
|---|---|---|---|
| House | $280,000 | $275,000 | $300,000 |
| Painting | $75,000 | $70,000 | $72,000 |
| Tractor | $56,000 | $60,000 | $63,000 |
| Total Bids | $411,000 | $405,000 | $435,000 |
| Fair Share | $137,000 | $135,000 | $145,000 |
| Owed to Estate | $218,000 | ||
| Estate Owes | $62,000 | $135,000 | |
| Share of Surplus | $7,000 | $7,000 | $7,000 |
| Final Share |
Gets painting and $69,000 cash |
Gets $142,000 cash | Gets house and tractor and pays $211,000 |
Alice gets the painting and $69,000 cash. Betty gets $142,000 cash. Charles gets the house and the tractor and pays $211,000 to the estate.
Now, we find the value of the final settlement for each of the three heirs in this example. Remember that each player has their own value system in this game so fair shares are not the same amount.
Alice: Painting worth $75,000 and $69,000 cash for a total of $144,000. This is $7,000 more than her fair share of $137,000.
Betty: $142,000 cash. This is $7,000 more than her fair share of $135,000.
Charles: House worth $300,000, tractor worth $63,000 and pays $211,000 for a total share of $152,000. This is $7,000 more that his fair share of $145,000.
At the end of the game, each player ends up with more than a fair share. It always works out this way as long as the assumptions are satisfied.
Summary of the Method of Sealed Bids:
- Each player privately and independently bids on each item. A bid is the amount the player thinks the item is worth.
- For each item, the player with the highest bid wins the item.
- For each player find the sum of the bids and divide this sum by the number of players to find the fair share for that player.
- Find the difference (fair share) – (total of items awarded) for each player. If the difference is negative, the player owes the estate that amount of money. If the difference is positive, the estate owes the player that amount of money.
- Find the surplus by finding the difference (sum of money owed to the estate) – (sum of money the estate owes). Divide the surplus by the number of players to find the fair share of surplus.
- Find the final settlement by adding the share of surplus to either the amount owed to the estate or the amount the estate owes. Include any items awarded and any cash owed in the final settlement. The sum of all the cash in the final settlement should be $0.
Example \(\PageIndex{2}\): Method of Sealed Bids, #2
Doug, Edward, Frank and George have inherited some furniture from their great-grandmother’s estate and wish to divide the furniture equally among themselves. Use the method of sealed bids to find a fair division of the furniture.
Note: We start with one table and add lines to the bottom as we go through the steps.
- List the bids in table form.
| Doug | Edward | Frank | George | |
|---|---|---|---|---|
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
- Award each item to the highest bidder.
| Doug | Edward | Frank | George | |
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
- Find the fair share for each player.
Doug:
Edward:
Calculate similarly for Frank and George.
| Doug | Edward | Frank | George | |
|---|---|---|---|---|
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
| Total Bids | $3,035.00 | $3,025.00 | $3,050.00 | $3,050.00 |
| Fair Share | $758.75 | $756.25 | $762.50 | $762.50 |
- Find the amount owed to the estate or the amount the estate owes.
Doug: \(\$ 758.75-\$ 1000.00=-\$ 241.25\)
Doug owes the estate $241.25.
Calculate similarly for Edward and Frank.
George: \(\$ 762.50-\$ 300.00=\$ 462.50\)
The estate owes George $462.50.
| Doug | Edward | Frank | George | |
|---|---|---|---|---|
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
| Total Bids | $3,035.00 | $3,025.00 | $3,050.00 | $3,050.00 |
| Fair Share | $758.75 | $756.25 | $762.50 | $762.50 |
| Owes to Estate | $241.25 | $393.75 | $87.50 | |
| Estate Owes | $462.50 |
- Find the share of surplus for each player.
| Doug | Edward | Frank | George | |
|---|---|---|---|---|
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
| Total Bids | $3,035.00 | $3,025.00 | $3,050.00 | $3,050.00 |
| Fair Share | $758.75 | $756.25 | $762.50 | $762.50 |
| Owes to Estate | $241.25 | $393.75 | $87.50 | |
| Estate Owes | $462.50 | |||
| Share of Surplus | $65.00 | $65.00 | $65.00 | $65.00 |
- Find the final share for each player.
Doug: \(-\$ 241.25+\$ 65.00=-\$ 176.25\)
Calculate similarly for Edward and Frank.
George: \(\$ 462.50+\$ 65.00=\$ 527.50\)
| Doug | Edward | Frank | George | |
|---|---|---|---|---|
| Dresser | $280.00 | $275.00 | $250.00 | $300.00 |
| Desk | $480.00 | $500.00 | $450.00 | $475.00 |
| Wardrobe | $775.00 | $800.00 | $850.00 | $800.00 |
| Dining Set | $1,000.00 | $800.00 | $900.00 | $950.00 |
| Poster Bed | $500.00 | $650.00 | $600.00 | $525.00 |
| Total Bids | $3,035.00 | $3,025.00 | $3,050.00 | $3,050.00 |
| Fair Share | $758.75 | $756.25 | $762.50 | $762.50 |
| Owes to Estate | $241.25 | $393.75 | $87.50 | |
| Estate Owes | $462.50 | |||
| Share of Surplus | $65.00 | $65.00 | $65.00 | $65.00 |
| Final Share | Dining set and pays $176.25 | Desk and poster bed and pays $328.75 | Wardrobe and pays $22.50 | Dresser and gets $527.50 |
Doug gets the dining set and pays $176.25. Edward gets the desk and poster bed and pays $328.75. Frank gets the wardrobe and pays $22.50. George gets the dresser and $527.50 in cash.
Note that the sum of all the money in the final shares is $0 as it should be. Also note that each player’s final share is worth $65.00 more than the fair share in his eyes.
Example \(\PageIndex{3}\): Method of Sealed Bids in Dissolving a Partnership
Jack, Kelly and Lisa are partners in a local coffee shop. The partners wish to dissolve the partnership to pursue other interests. Use the method of sealed bids to find a fair division of the business. Jack bids $450,000, Kelly bids $420,000 and Lisa bids $480,000 for the business.
Make a table similar to the table for dividing up an estate and follow the same set of steps to solve this problem.
| Jack | Kelly | Lisa | |
|---|---|---|---|
| Business | $450,000 | $420,000 | $480,000 |
| Total Bids | $450,000 | $420,000 | $480,000 |
| Fair Share | $150,000 | $140,000 | $160,000 |
| Owes to Business | $320,000 | ||
| Business Owes | $150,000 | $140,000 | |
| Share of Surplus | $10,000 | $10,000 | $10,000 |
| Final Share | $160,000 cash | $150,000 cash | Business and pays $310,000 |
Lisa gets the business and pays Jack $160,000 and Kelly $150,000.
Method of Markers
The method of markers is used to divide up a collection of many objects of roughly the same value. The heirs could use the method of markers to divide up their grandmother’s jewelry collection. The basic idea of the method is to arrange the objects in a line. Then, each player puts markers between the objects dividing the line of objects into distinct parts. Each part is a fair share to that particular player. Based on the placement of the markers, the objects are allotted to the players. If there are players, each player places markers among the objects. We will use notation A1 to represent the first marker for player A, A2 to represent the second marker for player A, and so on.
Many times when the players have done all the steps in the method of markers there are some objects left over. If many objects remain, the players can line them up and do the method of markers again. If only a few objects remain, a common approach is to randomly choose an order for the players, then let each player pick an object until all the objects are gone.
It is interesting to see that one player may only receive one or two objects while another player may receive four or five objects. The number of objects allotted depends on each player’s value system. First we will look at the allocation of the pieces after the markers have been placed. Once we understand that, we will look at placing the markers in the correct places for each player.
Example \(\PageIndex{4}\): Method of Markers, #1
Three players Albert (A), Bertrand (B), and Charles (C), wish to divide a collection of 15 objects using the method of markers. Determine the final allocation of objects to each player. Since there are three players, each player uses two markers.
Let’s start by looking at the line of objects and Albert’s markers.
The markers divide the line of objects into three pieces. Each piece of the line is a fair share in Albert’s value system. He would be satisfied with any of the three pieces in the final allocation. For now, do not worry about how Albert determined where to place the markers. We will look at that in Example \(\PageIndex{6}\).
Now let’s add the markers for Bertrand and Charles.
Step 1: As you examine the objects from left to right, find the first marker, B1. Give Bertrand all the objects from the beginning of the line to the marker B1. Bertrand removes the rest of his markers and leaves the game for now.
Step 2: Now, continuing from left to right, find the first marker out of the second group of markers (A2 and C2). The first marker from this group we come across is A2. Give Albert all the objects from his first marker A1 to his second marker A2. Remember that a fair share is from one marker to the next. Object #4 is not part of Albert’s fair share since it is before his first marker. Albert removes the rest of his markers and leaves the game for now.
Step 3: Charles is the only player left in the game. He considers everything from his second marker to the end of the line to be a fair share so give it to him. Any objects not allocated at this point are left over.
Step 4: Typically some objects are left over at this point. Objects numbered 4, 9, 10 and 11 are left over in this game. The three players could draw straws to determine an order. Then each player in order would choose an object until all the object are allocated.
Note: Normally when we do the method of markers, we only draw the figure once.
Summary of the Method of Markers for n players:
- Arrange the objects in a line. Each of the n players places n-1 markers among the objects.
- Find the 1st first marker, say A1. Give player A all the objects from the beginning of the line to the 1st first marker. Player A removes his/her remaining markers and leaves the game for now.
- Find the 1st second marker, say B2. Give player B all the objects from the 1st second marker back to B’s previous marker B1. In other words, all the objects from B1 to B2. Player B removes his/her remaining markers and leaves the game for now.
- Find the 1st third marker, say C3. Give player C all the objects from the 1st third marker back to C’s previous marker C2. In other words, all the objects from C2 to C3. Player C removes his/her remaining markers and leaves the game for now.
- Continue this pattern until one player remains. Give the last player all the objects from his/her last marker to the end of the line of objects.
- Divide up the remaining objects. If many objects remain, do the method of markers again. If only a few objects remain, randomly choose an order then let each player choose an object in order until all the objects are gone.
Example \(\PageIndex{5}\): Method of Markers, #2
Four cousins, Amy, Becky, Connie and Debbie wish to use the method of markers to divide a collection of jewels. The jewels are lined up and the cousins place their markers as shown below in Figure \(\PageIndex{23}\). What is the final allocation of the jewels?
The 1st first marker is C1 so give Connie all the jewels from the beginning of the line to her first marker. Connie removes her remaining markers and leaves the game for now.
The 1st second marker is D2 so give Debbie all the jewels between markers D1 and D2. Debbie removes her remaining markers and leaves the game for now.
The 1st third marker is a tie between A3 and B3 so randomly choose one. One possibility is to have Amy and Becky toss a coin and the winner gets the next fair share. Assume Becky wins the coin toss. Give Becky all the jewels between markers B2 and B3. Becky removes her remaining markers and leaves the game for now.
Amy is the last player in the game. Give Amy all the jewels from her last marker to the end of the line.
Jewels numbered 4, 8, and 9 are left over. The players can draw straws to determine an order. Each player, in order, chooses a jewel until all the jewels have been allocated.
Example \(\PageIndex{6}\): Determining Where to Place the Markers
Four roommates want to split up a collection of fruit consisting of 8 oranges (O), 8 bananas (B), 4 pears (P), and 4 apples (A). The fruit are lined up as shown below in Figure \(\PageIndex{28}\).
To determine where to place the markers, each player assigns a value to each type of fruit. Jack loves oranges, likes apples and pears equally, but dislikes bananas. He assigns a value of $1 to each apple and each pear, a value of $2 to each orange, and a value of $0 to each banana. In Jack’s value system, the collection of fruit is worth $24. Jack’s fair share is $6. He needs to place his markers so that the fruit is divided into groups worth $6. It can be helpful to work from both ends of the line. Jack has no choice about the placement of his first and third markers. Because he sees the bananas as worth $0 he has three possible places for his second marker. These possibilities are shown below in Figure \(\PageIndex{29}\) as dotted lines.
Kent dislikes apples and oranges, like bananas and really loves pears. He assigns a value of $0 to each apple or orange, a value of $1 to each banana, and a value of $3 to each pear. In Kent’s value system, the collection of fruit is worth $20. Since there are four players, Kent’s fair share is $5. He needs to place his markers so that the fruit is divided into groups worth $5. Jack has no choice about the placement of his third marker. He has a few possibilities for his first two markers. The possibilities are shown below in Figure \(\PageIndex{30}\) as dotted lines.
The other two roommates would follow the same process to place their markers. Once all the markers are placed, the allocation by the method of markers begins.
Imagine if the order of the fruit in Example \(\PageIndex{6}\) was rearranged. It might not be possible for Kent to divide up the line of fruits into groups worth $5. He might have to use a group worth $6 next to a group worth $4. This is a good time to remember that none of our fair division methods are perfect. They work well most of the time but sometimes we just have to make do. If Kent was allocated a group of fruit worth only $4 he might get some of the missing value back when the left over fruits are allocated.


12: Static Equilibrium and Elasticity
In earlier sections, you learned about forces and Newton’s laws for translational motion. You then studied torques and the rotational motion of a body about a fixed axis of rotation. You also learned that static equilibrium means no motion at all and that dynamic equilibrium means motion without acceleration. In this section, we combine the conditions for static translational equilibrium and static rotational equilibrium to describe situations typical for any kind of construction. What type of cable will support a suspension bridge? What type of foundation will support an office building? Will this prosthetic arm function correctly? These are examples of questions that contemporary engineers must be able to answer.
-
- 12.1: Prelude to Static Equilibrium and Elasticity
- The elastic properties of materials are especially important in engineering applications, including bioengineering. For example, materials that can stretch or compress and then return to their original form or position make good shock absorbers. In this chapter, you will learn about some applications that combine equilibrium with elasticity to construct real structures that last.
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- 12.2: Conditions for Static Equilibrium
- A body is in equilibrium when it remains either in uniform motion (both translational and rotational) or at rest. Conditions for equilibrium require that the sum of all external forces acting on the body is zero, and the sum of all external torques from external forces is zero. The free-body diagram for a body is a useful tool that allows us to count correctly all contributions from all external forces and torques acting on the body.
-
- 12.3: Examples of Static Equilibrium
- In applications of equilibrium conditions for rigid bodies, identify all forces that act on a rigid body and note their lever arms in rotation about a chosen rotation axis. Net external forces and torques can be clearly identified from a correctly constructed free-body diagram. In setting up equilibrium conditions, we are free to adopt any inertial frame of reference and any position of the pivot point. We reach the same answer no matter what choices we make.
-
- 12.4: Stress, Strain, and Elastic Modulus (Part 1)
- External forces on an object cause its deformation, which is a change in its size and shape. The strength of the forces that cause deformation is expressed by stress. The extent of deformation under stress is expressed by strain, which is dimensionless. Tensile (or compressive) stress, which causes elongation (or shortening) of the object or medium and is due to external forces acting along only one direction perpendicular to the cross-section.
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- 12.5: Stress, Strain, and Elastic Modulus (Part 2)
- Bulk stress causes a change in the volume of an object or medium and is caused by forces acting on the body from all directions, perpendicular to its surface. Compressibility of an object or medium is the reciprocal of its bulk modulus, the elastic modulus in this case. Shear strain is the deformation of an object or medium under shear stress. Shear stress is caused by forces acting along the object’s two parallel surfaces.
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- 12.6: Elasticity and Plasticity
- An object or material is elastic if it comes back to its original shape and size when the stress vanishes. In elastic deformations with stress values lower than the proportionality limit, stress is proportional to strain. An object or material has plastic behavior when stress is larger than the elastic limit. In the plastic region, the object does not come back to its original size or shape when stress vanishes but acquires a permanent deformation. Plastic behavior ends at the breaking point.
Thumbnail: Balanced Rock in Garden of the Gods. (CC BY-SA 2.5; Ahodges7 ).


6.1: Bacterial Susceptibility to Antibiotics (Kirby-Bauer Test)
- Define "antibiotic" and differentiate between broad-spectrum and narrow-spectrum antibiotics.
- Explain the purpose of the Kirby-Bauer test.
- Define "zone of inhibition."
- Interpret zone of inhibition results to determine the susceptibility or resistance of bacterial isolates to specific antibiotics.
- Apply knowledge of bacterial growth and diffusion patterns to interpret zone sizes and make informed decisions regarding antibiotic effectiveness.
- Describe the clinical significance of antibiotic susceptibility testing in guiding appropriate antimicrobial therapy.
- Discuss why antibiotic resistance is a threat.
Introduction to Antibiotics
Antibiotics are chemicals produced by certain bacteria and fungi that can inhibit bacterial growth. Since World War II, the discovery of antibiotics has been crucial in treating infections. By studying these natural chemicals, scientists have developed other antimicrobial agents, either completely synthesized in the lab (synthetic) or partly derived from natural sources and modified in the lab (semisynthetic).
Numerous microbes can produce antibiotics, but four key genera are the source of most antibiotics used to treat infections in humans and animals. The bacterial genera Bacillus and Streptomyces , along with the fungal genera Penicillium and Cephalosporium , are particularly significant. With the rise of microbial resistance, creating new antibiotics remains a persistent challenge.
The spectrum of activity of an antibiotic refers to the range of bacteria it can eliminate. Narrow-spectrum antibiotics are effective against either Gram-positive or Gram-negative bacteria, while broad-spectrum antibiotics target a wide variety of bacteria. However, broad-spectrum antibiotics contribute to the rising problem of drug resistance in microorganisms. These antibiotics can also disrupt a patient’s normal microbiome, leading to superinfections from organisms like Candida albicans and Clostridium difficile , which proliferate when they no longer have to compete with the normal microbiota.
Empiric therapy involves prescribing an antimicrobial agent without first conducting diagnostic tests, such as a culture, to identify the specific cause of infection. This approach is used when the pathogen is likely known and diagnostic tests wouldn’t change the treatment plan. Such therapy typically involves broad-spectrum antibiotics to cover a wide range of potential pathogens. This method is often employed for conditions like strep throat, pneumonia, urinary tract infections, and suspected bacterial meningitis.
However, physicians are increasingly opting for narrow-spectrum antibiotics to target infections more precisely. For instance, Isoniazid is a narrow-spectrum antibiotic used to treat tuberculosis caused by Mycobacterium tuberculosis . Clinical microbiologists play a key role in helping physicians select the most effective antimicrobial agent for a patient’s infection. One commonly used method to determine this is the Kirby-Bauer Test .
Kirby-Bauer Test
The results of the Kirby-Bauer test provide an accurate prediction of which antibiotics are likely to be effective against the pathogen. Because the Kirby-Bauer test is relatively simple to perform and is inexpensive, it has been extensively used in medical practice. The results are reported as S ( sensitive [i.e., susceptible] ), I ( intermediate ), and R ( resistant ) to an antibiotic.  An intermediate result indicates the antibiotic must be used in combination with another antibiotic to clear the infection or given at a higher dosage over a longer period. A resistant result indicates the antibiotic does not kill the bacteria.
Petri plates with Mueller Hinton agar are used to test bacterial sensitivity to antibiotics. After spreading the bacteria across the entire surface of the plate (a process called creating a bacterial lawn), small disks containing various antibiotics are placed at spaced intervals 4-5 cm apart. Each antibiotic diffuses outward from its disk, forming a concentration gradient with the highest concentration nearest the disk and decreasing concentrations further away. Depending on the bacteria's sensitivity to each antibiotic, growth will be inhibited at specific concentrations. Bacteria able to grow close to the disk, where concentrations are highest, are more resistant to that antibiotic. In contrast, bacteria that can only grow farther away, where concentrations are lower, are more susceptible. The size of the zone of inhibition —an area around the disk where no bacterial growth occurs—indicates whether the bacteria are sensitive, intermediate, or resistant to the antibiotic.
The Kirby-Bauer test must be carefully controlled to ensure accurate interpretation of the results. Factors such as antibiotic stability, diffusion rate, the type of bacteria tested, the pH and depth of the culture medium, inoculum density, incubation time, temperature, and antibiotic concentration can all influence the outcome. However, when the Kirby-Bauer test is conducted under standardized conditions (using Mueller-Hinton agar inoculated with a pure culture at the correct turbidity matching the McFarland 0.5 standard, for example) and interpreted according to the Interpretative Zone Standards from the National Committee for Clinical Laboratory Standards, it provides reliable data. In this lab, a simplified, non-standardized version of the Kirby-Bauer test will be used to help you understand the basic principles of the procedure.
Antibiograms: Taking Some of the Guesswork Out of Prescriptions
Unfortunately, infectious diseases don’t take a time-out for lab work. As a result, physicians rarely have the luxury of conducting susceptibility testing before they write a prescription. Instead, they rely primarily on the empirical evidence (i.e., the signs and symptoms of disease) and their professional experience to make an educated guess as to the diagnosis, causative agent(s), and drug most likely to be effective. This approach allows treatment to begin sooner so the patient does not have to wait for lab test results. In many cases, the prescription is effective; however, in an age of increased antimicrobial resistance, it is becoming increasingly more difficult to select the most appropriate empiric therapy. Selecting an inappropriate empiric therapy not only puts the patient at risk but may promote greater resistance to the drug prescribed.
Recently, studies have shown that antibiograms are useful tools in the decision-making process of selecting appropriate empiric therapy. An antibiogram is a compilation of local antibiotic susceptibility data broken down by bacterial pathogen. In a November 2014 study published in the journal Infection Control and Hospital Epidemiology , researchers determined that 85% of the prescriptions ordered in skilled nursing facilities were decided upon empirically, but only 35% of those prescriptions were deemed appropriate when compared with the eventual pathogen identification and susceptibility profile obtained from the clinical laboratory. However, in one nursing facility where use of antibiograms was implemented to direct selection of empiric therapy, appropriateness of empiric therapy increased from 32% before antibiogram implementation to 45% after implementation of antibiograms. 25 Although these data are preliminary, they do suggest that health-care facilities can reduce the number of inappropriate prescriptions by using antibiograms to select empiric therapy, thus benefiting patients and minimizing opportunities for antimicrobial resistance to develop.
Laboratory Instructions
Kirby-Bauer Test for Antibiotic Sensitivity
- Label one Mueller Hinton agar (MHA) plate with your group name, the bacterial species, course section, and date. Using a sterile cotton swab, collect an inoculum from the culture provided by your instructor. Be sure to use the lid as a shield to prevent airborne contamination.
- Inoculate the MHA plate by evenly spreading the sample across the entire agar surface to create a bacterial lawn.
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Using tweezers and antibiotic dispensers, gently place four antibiotic disks onto the plate. Do not press the disks into the agar or move them once placed. Ensure proper spacing between the disks (4-5 cm).The available antibiotics are:
- Penicillin (P10) 10 Units
- Trimethoprim (SXT) 1.25 µg
- Ciprofloxacin (CIP5) 5 µg
- Chloramphenicol (C30) 30 µg
- Tetracycline (TE30) 30 µg
- Erythromycin (E15) 15 µg
4. Place the Petri plates in the incubator without inverting them. After 24-48 hours of incubation, measure the zones of inhibition in millimeters and record the results in the results table. Refer to the interpretation table to determine whether the bacterial strain is susceptible, intermediate, or resistant to each antibiotic based on the zone of inhibition size.
| antibiotic disk abbreviation | antibiotic name | antibiotic disk concentration |
resistant (mm) |
intermediate (mm) |
susceptible (mm) |
| E15 | Erythromycin | 15 µg | 13 or less | 14 – 22 | 23 or more |
| CIP5 | Ciprofloxacin | 5µg | 15 or less | 16 - 20 | 21 or more |
| SXT | Trimethoprim | 1.25µg | 10 or less | 11 - 15 | 16 or more |
| P10 |
Penicillin ( Staphylococcus) |
10 U | 28 or less | 29 or more | |
| P10 |
Penicillin (other bacteria) |
10 U | 14 or less | 15 or more | |
| C30 | Chloramphenicol | 30 µg | 12 or less | 13 – 17 | 18 or more |
| TE30 | Tetracycline | 30 µg | 14 or less | 15 – 18 | 19 or more |
Attributions
- Agar Diffusion Method 1.jpg by Sommer36 is licensed under CC BY-SA 4.0
- Testing the Effectiveness of Antimicrobials by OpenStax is licensed under Creative Commons Attribution License . Access for free at https://openstax.org/books/microbiology/pages/1-introduction )
- Red Mountain Microbiology by Jill Raymond Ph.D.; Graham Boorse, Ph.D.; and Anne Mason M.S. is licensed under CC BY-NC 4.0
Citations
- J.P. Furuno et al. “Using Antibiograms to Improve Antibiotic Prescribing in Skilled Nursing Facilities.” Infection Control and Hospital Epidemiology 35 no. Suppl S3 (2014):S56–61.


9.9: Personal Application Questions
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22 .
Reflect on your own physical development during adolescence. Did you experience any significant growth spurts or changes? How did these changes impact your self-esteem and interactions with peers?
23 .
Think about the times when you made decisions during your adolescence that you now see differently as an adult. How do you think the development of your brain at that time influenced your decision-making process?
24 .
Consider the health care you received during adolescence. Did you feel that your health-care needs were adequately met, and were you comfortable discussing personal health issues with your provider? If not, what do you think could have made the experience better?
25 .
How did your sleep patterns change during adolescence? Do you think you were getting enough sleep?
26 .
Reflect on your experience of learning about puberty. Did you feel prepared for the changes you went through, or did you find them surprising? What, if anything, would have helped you feel more comfortable or informed during that time?
27 .
 How did these messages shape your views on sexual behavior?
28 .
Consider the role of peer pressure in sexual decision-making.  How did you handle that situation, and what did you learn from it?
29 .
Reflect on the portrayal of adolescent sexual behavior in media and popular culture. How do these portrayals compare to your own experiences or the experiences of those around you? What effect do you think these portrayals have on adolescents’ sexual health and behavior?
30 .
Reflect on a time during your adolescence when you found yourself thinking about abstract concepts like justice, equality, or truth. How did your understanding of these concepts evolve as you grew older, and what experiences or influences contributed to that change?
31 .
Consider a situation in which you had to make a difficult decision during your teenage years. How did you approach the problem, and how did your ability to think through different possibilities influence the outcome?
32 .
Recall a time when you felt strongly about questioning or challenging a rule or belief held by your parents or teachers. What was the situation, and how did your cognitive development at the time influence your reaction and reasoning?
33 .
Think about an instance where you felt that everyone was watching or judging you (an “imaginary audience”). How did this belief affect your behavior or decisions at the time, and how do you view that experience now?
34 .
Think back to a time during your adolescence when you were faced with a decision involving potential risk. What factors influenced your decision? Did you consider the possible consequences, or were you more focused on the immediate rewards? How did the outcome of this decision shape your perspective on risk-taking?
35 .
Reflect on a situation where you felt peer pressure to engage in a risky behavior. How did the presence of your peers affect your risk assessment and decision-making? Looking back, would you have made the same decision if you were alone? Why or why not?
36 .
Consider how your decision-making process has changed from adolescence to now. What are some specific ways in which you believe your ability to assess risks and rewards has matured? Provide an example of a recent decision that illustrates this change.


11.2: Rolling Motion
When considering objects that can move both translationally (up, down, left, right, in, out!) and rotationally, we are immediately confronted with a problem: these two motions can be either completely independent, completely related to each other, or something even in-between. Take for example a baseball thrown by a pitcher. It follows a particular path from the mound to the plate (its translational motion), but it might also have some spin (it's rotational motion). Those seem pretty independent, but in fact spinning balls like that can swerve back in forth because of something called The Magnus Effect (check it out on Wikipedia ). Of course, that's why pitchers make the ball do that, is that motion makes it more complicated for the batter to hit the ball. The problem is that coupling between the air and the ball is weak in some sense - most of the energy of the ball is used for it's forward motion, only a small amount is used to make the ball move back and forth through the air.
Naturally, we would like to understand those kinds of interesting situations, but they end up being rather complicated. We would like to start with something simpler - motion in which the translation and rotation are either completely independent, and can be solved completely separately, or they are easily related to each other. If they are independent, you can solve them based on what you know already! However, there is a case in which the motions are completely related to each other, and is very common, called rolling without slipping . In this case, the translational motion and the rotational motion are coupled, and the relevant velocities are related to each other:
\[ | \vec v_{cm} | = R |\omega| \label{eq:9.34} .\]
Here \(R\) is the radius of the entire object. Notice how this expression relates to Equation ( 6.1.1 ) from a previous section - they look very similar, but they are actually saying two somewhat different things. Equation ( 6.1.1 ) told us the relationship between the angular and linear speed of a particular point on an object, while the expression above tells us how to related the angular and linear speed of the entire object (remember that the center of mass is the location at which the object is, if the object was a single point).
The origin of the condition (\ref{eq:9.34}) is fairly straightforward. You can imagine an object that is rolling without slipping as “measuring the surface” as it rolls (or vice-versa, the surface measuring the circumference of the object as its different points are pressed against it in succession). So, after it has completed exactly one revolution (\(2\pi\) radians), it should have literally “covered” a distance on the surface equal to \(2\pi R\), that is, advanced a distance \(2\pi R\). But the same has to be true, proportionately, for any rotation angle \(\Delta \theta\) other that \(2\pi\): since the length of the corresponding arc is \(s = R|\Delta \theta|\), in a rotation over an angle \(|\Delta \theta|\) the center of mass of the object must have advanced a distance \(|\Delta x_{cm}| = s = R|\Delta \theta|\). Dividing by \(\Delta t\) as \(\Delta t \rightarrow 0\) then yields Equation (\ref{eq:9.34}).
Considering a single rolling objects, the total kinetic energy can now be written as two terms,
\[K=K_{rot}+K_{cm}=\frac{1}{2}I\omega^2 +\frac{1}{2}mv_{cm}^2\]
combining this with the condition of rolling without slipping (\ref{eq:9.34}), we see that the ratio of the translational to the rotational kinetic energy is
\[ \frac{K_{c m}}{K_{r o t}}=\frac{m v_{c m}^{2}}{I \omega^{2}}=\frac{m R^{2}}{I} \label{eq:9.43} .\]
The amount of energy available to interact with the object is whatever potential energy is running around the system, and that has to be split between translational and rotational in the proportion (\ref{eq:9.43}). An object with a proportionately larger \(I\) is one that, for a given angular velocity, needs more rotational kinetic energy, because more of its mass is away from the rotation axis. This leaves less energy available for its translational motion.


9.1: Introduction to Employee Diversity
What you’ll learn to do: identify the advantages and challenges of employee diversity within organizations
America is an incredibly diverse country, with residents and citizens from virtually every part of the world. Colleges and universities are perhaps even more diverse than communities. Undergraduate and graduate students travel from Asia, Europe, Africa, and South America to study in the United States. American workplaces are also increasingly diverse, particularly when companies work with or have divisions in other countries. There are great benefits to diversity, but differences can also create challenges.
Contributors and Attributions
CC licensed content, Original
- Introduction to Employee Diversity. Authored by : Lisa Jo Rudy and Lumen Learning. License : CC BY: Attribution


16.15: Regulating Gene Expression in Cell Development - Establishing Body Axes during Development
- Summarize the mechanisms and cell types that establish the body axes
Vertebrate axis formation
During development, as the germ layers form, the ball of cells still retains its spherical shape. However, animal bodies have lateral-medial (left-right), dorsal-ventral (back-belly), and anterior-posterior (head-feet) axes. How are these established? In one of the most seminal experiments ever to be carried out in developmental biology, Spemann and Mangold took dorsal cells from one embryo and transplanted them into the belly region of another embryo. They found that the transplanted embryo now had two notochords: one at the dorsal site from the original cells and another at the transplanted site. This suggested that the dorsal cells were genetically programmed to form the notochord and define the axis. Since then, researchers have identified many genes that are responsible for axis formation. Mutations in these genes leads to the loss of symmetry required for organism development. Animal bodies have externally visible symmetry. However, the internal organs are not symmetric. For example, the heart is on the left side and the liver on the right. The formation of the central left-right axis is an important process during development. This internal asymmetry is established very early during development and involves many genes. Research is still ongoing to fully understand the developmental implications of these genes.
Neural tube
In the developing chordate (including vertebrates), the neural tube is the embryo’s precursor to the central nervous system, which comprises the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube, the neural tube or neural canal, the ectodermal wall of which forms the rudiment of the nervous system.
Primary and secondary neurulation
The neural tube develops in two ways: primary neurulation and secondary neurulation. Primary neurulation divides the ectoderm into three cell types: the internally located neural tube, the externally located epidermis, and the neural crest cells, which develop in the region between the neural tube and epidermis but then migrate to new locations. Primary neurulation begins after the neural plate forms. The edges of the neural plate start to thicken and lift upward, forming the neural folds. The center of the neural plate remains grounded, allowing a U-shaped neural groove to form. This neural groove sets the boundary between the right and left sides of the embryo. The neural folds pinch in towards the midline of the embryo and fuse together to form the neural tube. In secondary neurulation, the cells of the neural plate form a cord-like structure that migrates inside the embryo and hollows to form the tube.
Each organism uses primary and secondary neurulation to varying degrees. Neurulation in fish proceeds only via the secondary form. In avian species the posterior regions of the tube develop using secondary neurulation and the anterior regions develop by primary neurulation. In mammals, secondary neurulation begins around the 35th somite. Mammalian neural tubes close in the head in the opposite order that they close in the trunk. In the head, neural crest cells migrate, the neural tube closes, and the overlying ectoderm closes. In the trunk, overlying ectoderm closes, the neural tube closes and neural crest cells migrate.
Neural tube subdivisions
Four neural tube subdivisions eventually develop into distinct regions of the central nervous system by the division of neuroepithelial cells: the prosencephalon, the mesencephalon, the rhombencephalon and the spinal cord. The prosencephalon further goes on to develop into the telencephalon (the forebrain or cerebrum) and the diencephalon (the optic vesicles and hypothalamus). The mesencephalon develops into the midbrain. The rhombencephalon develops into the metencephalon (the pons and cerebellum) and the myelencephalon (the medulla oblongata).
For a short time, the neural tube is open both cranially and caudally. These openings, called neuropores, close during the fourth week in the human. Improper closure of the neuropores can result in neural tube defects such as anencephaly or spina bifida. The dorsal part of the neural tube contains the alar plate, which is primarily associated with sensation. The ventral part of the neural tube contains the basal plate, which is primarily associated with motor (i.e., muscle) control.
Signaling molecules and other factors
The neural tube patterns along the dorsal-ventral axis establish defined compartments of neural progenitor cells that lead to distinct classes of neurons. This patterning occurs early in development and results from the activity of several secreted signaling molecules. Sonic hedgehog (Shh) is a key player in patterning the ventral axis, while Bone morphogenic proteins (Bmp) and Wnt family members play an important role in patterning the dorsal axis. Other factors shown to provide positional information to the neural progenitor cells include Fibroblast growth factors (FGF) and Retinoic Acid. Retinoic acid is required ventrally along with Shh to induce Pax6 and Olig2 during differentiation of motor neurons. Three main ventral cell types are established during early neural tube development: the floor plate cells, which form at the ventral midline during the neural fold stage; as well as the more dorsally located motor neurons and interneurons. These cell types are specified by the secretion of Shh from the notochord (located ventrally to the neural tube), and later from the floor plate cells. Shh acts as a morphogen, meaning that it acts in a concentration-dependent manner to specify cell types as it moves further from its source. The different combinations of expression of transcription factors along the dorsal-ventral axis of the neural tube are responsible for creating the identity of the neuronal progenitor cells.
Key Points
- The three axes of the animal body are established in development via the expression of specific sets of genes that regulate which cells will develop into specific structures.
- During development, the dorsal cells are genetically programmed to develop into the notochord and define the axis.
- The neural tube can develop in two ways: primary or secondary neurulation, which are used by organisms in varying degrees to establish the neural tube that will develop into the central nervous system (brain and spinal cord).
- Specific patterns along the neural tube that are established via secretion and production of specific signaling molecules (such as Wnt, Shh, BMP and retinoic acid) play a key role in patterning the dorsal and ventral axes.
Key Terms
- neural tube : hollow longitudinal dorsal tube formed in the folding and subsequent fusion of the opposite ectodermal folds in the embryo that gives rise to the brain and spinal cord
- neurulation : the process by which the beginnings of the vertebrate nervous system is formed in embryos
- anencephaly : a lethal birth defect in which most of the brain and parts of the skull are missing; absence of the encephalon
- notochord : a flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive spine


14.14: Transferable Skills
- List transferable skills that will be valuable for any career path
Transferable (soft) skills may be used in multiple professions. In looking at this page for transferable skills, which are largely soft skills, start to think about the ones that apply to you and that you might refer to in your employment documents or employment conversations.
They include, but are by no means limited to, skills listed below:
| Dependable and punctual (showing up on time, ready to work, not being a liability) | Self-motivated | Enthusiastic |
| Willing to learn (lifelong learner) | Committed | A good problem solver |
| Adaptable (willing to change and take on new challenges) | Strong in customer service skills | A team player |
| Good in essential work skills (following instructions, possessing critical thinking skills, knowing limits) | Positive attitude | Strong communication skills |
| Able to accept constructive criticism | Ethical | Safety-conscious |
| Strong in time management | Honest |
These skills are transferable because they are positive attributes that are invaluable in practically any kind of work. They also do not require much training from an employer—you have them already and take them with you wherever you go.  This is not to suggest that either you’re born with these skills or you’re not. Each of the skills listed above is different, and you will be stronger in some than in others. In addition, soft skills can be worked on and improved, and there are lots of resources to help develop them. Think of each soft skill like playing a sport—tennis, for example. Some people are inherently athletic and will pick up a racket and play well from their first time on a court. Other people will need lessons and lots of practice, but eventually, they can build up to a solid game—and have fun playing as well.
So, identify the soft skills that show you off the best, and identify the ones that prospective employers are looking for. By comparing both sets, you can more directly gear your job search to your strongest professional qualities.
10 Top Skills You Need to Get a Job When You Graduate
The following video summarizes the ten top skills that the Target corporation believes will get you a job when you graduate.You can read a transcript of the video “10 Top Skills That Will Get You a Job When You Graduate.” As you watch this video, begin to think about which of these skills you might have and how you will demonstrate them to a potential employer in your application documents and interviews.
How to Find a New Job–Transferable Job Skills
The following video covers similar information to the 10 Top Skills video above. Discover how to find a new job more easily by learning how to identify and describe your transferable job skills.
Remember, no one person is perfect for any job. Everyone has areas to emphasize and to de-emphasize.
For more extensive exploration of your skills check out the following sources:
- This checklist of transferable skills from Community Employment Services in Woodstock, Ontario.
- The My Skills My Future skills matcher, which asks you for a past or current job and finds jobs with similar skills.
- Careeronestop.org, which is (as it says in the name) your one stop for career exploration.
Contributors and Attributions
- Practice question. Authored by : Susan Kendall. Provided by : Lumen Learning. License : CC BY: Attribution
- College Success. Authored by : Linda Bruce. Provided by : Lumen Learning. Located at : https://courses.lumenlearning.com/waymaker-collegesuccess/ . License : CC BY: Attribution
- 10 top skills that will get you a job when you graduate. Authored by : TARGETjobs. Located at : https://youtu.be/jKtbaUzHLvw . License : All Rights Reserved . License Terms : Standard YouTube License
- How to find a new job Transferable Job Skills. Authored by : Learn English with Rebecca. Located at : https://youtu.be/7Kt4nz8KT_Y . License : All Rights Reserved . License Terms : Standard YouTube License