11.9: Summary
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Web accessibility is especially critical in education to ensure that all students have fair and equivalent access to learning materials. Government institutions in the US and UK are required by law to make their web content accessible. Standards and practices for accessibility are agreed upon by the W3C and implemented by the WAI.
Sight, hearing, mobility, and learning disabilities can affect how your students access and interpret information on the Web. Assistive technologies can help with some of the difficulties faced; some must be addressed by your website itself. When making an accessible site, start by thinking about its design, structure, and content.
It is neither quick nor easy to create multiple pathways to reach learning objectives in the online environment. It will take time to build up a set of online materials, activities, and assessment strategies that accommodates the wide variety of learning needs of students with disabilities and learning preferences of all students. Your efforts will create an inclusive space for everyone, including students traditionally marginalized by their needs in the online environment.
As the old saying goes, “You cannot please all of the people, all of the time.” In our case here, we are just trying to increase the probability that each student will succeed in our online course area, regardless of his or her disabilities, learning preferences, or life situation. We do this by increasing the number of methods by which students get and use the content. We do this, whenever possible, by giving options to students regarding how we will evaluate their performance. We do this by taking the time to engage students in different ways and at different levels. We do this by applying UDL principles to online teaching and learning.
Once you have taken UDL principles into consideration when developing your course materials, use correct XHTML and CSS—or a program that can generate this for you—to build or modify the site according to the guidelines provided by the WCAG. This will help to ensure that the technology does not create barriers for students with disabilities.
Case Studies
From 2005–2006, the University of British Columbia was involved in a BCcampus-funded project on web accessibility in online learning. During the project, we created a focus group of people with different disabilities. Based on their comments, modifications and redesigns were done on five courses that were piloted in summer 2006 as “accessible courses”. Where possible, we asked the participants to use their own computers at home, which were already adapted according to their usage and personal preferences. When in the office, we tried to imitate their home setting, giving them a choice of using Windows or Mac OS and their preferred browser. We wanted to avoid the additional barriers of working on a new computer in an unknown environment, and for participants to experience the same situation as our registered students. Therefore, our introductions and instructions were limited to what they would get from an instructor in advance. We only limited their browsing by asking them to focus on specific pages rather than reading the whole course content. Focus group members were interviewed individually before and after the modifications. The first set of questions was about how their disability affected their ability to navigate the course material and what improvements would make the material more accessible for them. Questions after the modifications involved quality of the presentation, usability of the interface and usefulness of the system.
In our consultations with the participants, we asked them for their oral or written feedback and opinions on their experience. The names in these cases have been changed for privacy reasons.
Case 1: Samuel
Description. Samuel is a hard-of-hearing English as a Second Language (ESL) student from Korea. Online courses had been recommended to him as a good choice to remove the barrier of his impairment.
Issues. Samuel was surprised and disappointed with the amount of text-based material in the courses that he took. He compared them with the online courses in Korea, which included a considerable amount of video excerpts. Because English is not his native language,
Samuel struggles in traditional classroom classes. Despite that, he would rather meet face-to-face, or use a webcam to see emotions and gestures, than attempt to pick them up from text alone. Comment and recommendation. Making content text-only does not necessarily make it more accessible. It works well with a screen reader, but there is no benefit for a hearing-impaired student. Instead of omitting all the media, more attention should be devoted to providing alternatives to pure audio, such as transcripts, or captions for video components. See the example in Figure \(\PageIndex{1}\) where a video segment is accompanied by transcripts and audio.
Webcam support is a common feature in instant messaging software, and students are increasingly comfortable with its use. While not every student can reasonably be expected to own a webcam, video messaging supported by text messaging would be of greater benefit to Samuel than a standard text-based forum, allowing him not only to see others’ facial expressions, but also to encounter and practise spoken English at a functional level.
Case 2: Ted
Description. Ted is an ESL teacher with a condition which causes his eyeballs to continue rotating when focusing on an object. He does not often use a computer, as he has to learn programs by memory rather than use visual cues. He finds himself lost when searching on the Internet.
Issues. For Ted, text tends to wobble: small text is very difficult to read, and line spacing must be great enough to clearly separate the lines. Ted increases the font size in his browser when reading from the Web.
Comment and recommendation. One of the main goals here was to help Ted focus on the page. The layout of the pages was improved and made easier to read, with shorter line length and greater line spacing. The graphics that are too small have a “magnifying glass” option to zoom the image. See example in Figure 11.8.
Location cues are critically important for Ted. This was implemented by highlighting the title of the current page in the left-hand navigation menu. This is a benefit not only for those with visual impairments, who can refer to the highlighted line as a visual bookmark, but also for people with learning disabilities or those whose native language is not English, who benefit from the reinforcement of location information in the title and navigation menu of the page.
Use of a screen reader, such as Wynn, is recommended. The tool highlights the lines of text currently being read. Ted uses his finger to follow the line of text. This software will help his eyes focus on the highlighted portion of the content, as well as provide an audio option.
Case 3: Robert
Description. Robert had nerve damage to his right hand and cannot use a standard keyboard. A standard mouse is also difficult for him to use, so he usually uses a tablet. He recently acquired a Frogpad, a one-handed, 20-key keyboard that uses key combinations. So far he can type about 10 to 20 words per minute.
Issues. Robert requires additional time when writing exams, especially when handwriting; he prefers to type even though it is still slow. He says he would be unlikely to use a discussion board or chat room. To date, he has not used voice tools, but says he could not use them in a crowded lab.
Comment and recommendation. Making special arrangements for assignments, such as extending the deadline, or submitting it in a different format is a solution that has to be discussed with an instructor. Students who have problems and need special accommodations often do not report them to their instructors. A note coming from the instructor or administrator at the beginning of the course, explaining the possibilities of those accommodations, will encourage students to express their concerns.
Introducing audio tools, such as voice discussion boards or voice instant messaging, may save Robert’s typing time and effort. If access to the necessary hardware could be obtained, assignments that can optionally be submitted in alternative formats, such as audio or video presentations, may also be appropriate.
Case 4: George
Description. George has been blind since birth, and relies on a computer with JAWS for Windows, a talking screen reader program, which enables him to access the Internet as well as many other PC applications.
Issues. George has taken courses online in the past, but finds WebCT cumbersome to navigate. The popular course management system is based on framesets, which are not optimal for JAWS, as when a single frame updates it is difficult for a blind listener to determine what has changed on the page. Navigation is distributed across multiple framesets and implemented in JavaScript, which behaves differently in the JAWS reader than standard HTML.
Comment and recommendation. Many of the improvements that can help students such as George are the familiar guidelines of the WCAG. Here, the challenge is not simply to adapt the material, but to make course developers aware that these changes are necessary.
George, who is interested in a radio broadcasting career, was asked if he would prefer to submit assignments as audio readings rather than written assignments. He responded that the material for an audio reading must either be prepared as written text in advance or else the final audio must be edited, which is a less accessible option for a blind user than a standard text editor. Nevertheless, he was appreciative of the idea of offering students alternatives.


12.4: The Volume-Temperature Law
- Understand the relationship between volume of a gas and temperature.
Consider a gas under constant pressure in a cylinder with a piston in Fig. 7.3.1. Increasing temperature increases the average kinetic energy ( KE ) of the gas molecules. This results in more forceful collisions inside the chamber. The gas volume starts to increase since the pressure in the container does not change. In other words, increasing temperature increases the volume of the gas if the pressure and amount of gas are not changed.
If two related parameters increase or decrease together, they are directly proportional to each other.
Charles’s law states that the volume of a given amount of gas is directly proportional to the temperature in the Kelvin scale at constant pressure.
Fig. 12.4.2 demonstrates that the volume of a gas decreases when the gas is cooled down.
The mathematical forms of Charles’s law are the following.
\[V\propto{T}\nonumber\], or \[V=\mathrm{k}T\nonumber\], or \[\frac{V}{T}=\mathrm{k}\nonumber\]
, where k is a constant, V is volume, and T is the temperature (in kelvin scale) of the gas. Since \(\frac{V}{T}\) is a constant, it implies that
\[\frac{V_{1}}{T_{1}}=\frac{V_{2}}{T_{2}}=\mathrm{k}\nonumber\]
where V 1 is the initial volume, T 1 is the initial temperature in Kelvin, V 2 is the final volume, and T 2 is the final temperature in Kelvin, provided the amount of gas and pressure do not change. Note that the kelvin scale is used in Charles’s law because the kelvin scale does not have negative numbers. If the given temperature is not in the kelvin scale, first convert the temperature to the Kelvin scale and then use the gas laws for the calculations.
A sample of CO 2 occupies 3.23 L volume at 25.0 o C. Calculate the volume of the gas at 50.0 o C if pressure and amount of gas do not change?
Solution
Given: T 1 = 25.0 o C + 273.15 = 298.2 K, T 2 = 50.0 o C + 273.15 = 323.2 K, V 1 = 3.23 L, V 2 = ?
Formula: \(\frac{V_1}{T_1}=\frac{V_2}{T_2}\), rearrange the formula to isolate the desired variable: \(V_{2}=\frac{V_{1} T_{2}}{T_{1}}\)
Plug in the values in the rearranged formula and calculate: \(V_{2}=\frac{3.23 \mathrm{~L} \times 323.2 \mathrm{~K}}{298.2 \mathrm{~K}}=3.50 \mathrm{~L}\)
Applications
Car Tires
As winter approaches, the temperature drops rapidly. The volume of the tire decreases as temperature decreases. For every 10 o F decrease in temperature, the tire pressure decreases by 1 psi. It is important to keep your car tires inflated to the correct pressure to maximize gas mileage.
Hot Air Balloons
Charles’s law explains the drifting of warm air upward in the atmosphere. As the gas is warmed, its volume increases and its density decreases which makes the gas drift upward. A hot air balloon, shown in Fig. 12.4.3 operates using hot air.
Summary
The volume of a gas is directly proportional to the temperature in the Kelvin scale provided the pressure and amount of gas is not changed.


1.14.50: Osmotic Pressure
A semi-permeable membrane [1] separates an aqueous solution (where the mole fraction of water equals \(\mathrm{x}_{1}\)) and pure solvent at temperature \(\mathrm{T}\) and ambient pressure. Solvent water flows spontaneously across the membrane thereby diluting the solution. This flow is a consequence of the chemical potential of the solvent in the solution being lower than the chemical potential of pure solvent at the same \(\mathrm{T}\) and \(\mathrm{p}\). If a pressure (\(\mathrm{p} + \pi\)) is applied to the solution, the spontaneous process stops because the solution at pressure (\(\mathrm{p} + \pi\)) and the solvent at pressure \(\mathrm{p}\) are in thermodynamic equilibrium; \(\pi\) is the osmotic pressure. Thus at equilibrium,
\[\mu_{1}(\mathrm{aq} ; \mathrm{T} ; \mathrm{p}+\pi)=\mu_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}) \nonumber \]
Under this equilibrium condition solvent flows in both directions across the semi-permeable membrane but the net flow is zero. In the analysis presented here we take account of the fact, writing \(\mathrm{p}^{\prime}\) for (\(\mathrm{p} + \pi\)), the chemical potential of water in the aqueous solution is given by equation (b).
\[\begin{aligned}
&\mu_{1}^{\mathrm{eq}}\left(\mathrm{aq} ; \mathrm{T} ; \mathrm{p}^{\prime}\right)= \\
&\mu_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0)+\mathrm{p}^{\prime} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \mathrm{K}_{\mathrm{Tl}}^{*}(\ell) \, \mathrm{p}^{\prime}\right] \\
& \\
&+\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1} \, \mathrm{f}_{1}\right)
\end{aligned} \nonumber \]
Here \(\mathrm{f}_{1}\) is the activity coefficient expressing the extent to which the thermodynamic properties of water in the aqueous solution are not ideal. For the pure solvent water at pressure \(\mathrm{p}\) (i.e. on the other side the of the semi-permeable membrane),
\[\begin{aligned}
&\mu_{1}^{\mathrm{eq}}(\mathrm{aq} ; \mathrm{T} ; \mathrm{p})= \\
&\quad \mu_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0)+\mathrm{p}^{\prime} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{Tl}}^{*}(\ell) \, \mathrm{p}\right]
\end{aligned} \nonumber \]
But osmosis experiments explore an equilibrium characterized by equation (d).
\[\mu_{1}\left(\mathrm{aq} ; \mathrm{T} ; \mathrm{p}^{\prime}\right)=\mu_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}) \nonumber \]
Therefore using equations (b) and (c),
\[\begin{array}{r}
\mathrm{p}^{\prime} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}^{\prime}\right]+\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1} \, \mathrm{f}_{1}\right)= \\
\mathrm{p} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}\right]
\end{array} \nonumber \]
Or,
\[\begin{aligned}
&\mathrm{p} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}^{\prime}\right] \\
&-\mathrm{p} \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}\right]=-\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1} \, \mathrm{f}_{1}\right)
\end{aligned} \nonumber \]
The terms \(\mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}^{\prime}\right]\) and \(\mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p}=0) \,\left[1-(1 / 2) \, \kappa_{\mathrm{T} 1}^{*}(\ell) \, \mathrm{p}\right]\) describe the molar volumes of water at pressures \(\mathrm{p}\) and \(\mathrm{p}^{\prime}\); i.e. at pressure \(\mathrm{p}\) and (\(\mathrm{p}+\pi\)). We assume that both terms can be replaced by the molar volumes at average pressure \([(2 \, \mathrm{p}+\pi) / 2]\); namely \(\mathrm{V}_{1}^{*}[\ell ; \mathrm{T} ;(2 \, \mathrm{p}+\pi) / 2]\). Therefore
\[\pi \, \mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ;(2 \, \mathrm{p}+\pi) / 2]=-\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1} \, \mathrm{f}_{1}\right) \nonumber \]
In the event that \(\pi<<2 \, p\),
\[\pi \, \mathrm{V}_{1}^{*}[\ell ; \mathrm{T} ; \mathrm{p}]=-\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1} \, \mathrm{f}_{1}\right) \nonumber \]
If the thermodynamic properties of the solutions are ideal, \(\mathrm{f}_{1}\) equals unity. Then
\[\pi^{\mathrm{id}} \, \mathrm{V}_{1}^{*}[\ell ; \mathrm{T} ; \mathrm{p}]=-\mathrm{R} \, \mathrm{T} \, \ln \left(\mathrm{x}_{1}\right) \nonumber \]
In the latter two equations \(\mathrm{V}_{1}^{*}(\ell ; \mathrm{T} ; \mathrm{p})\) is treated as a constant, independent of the thermodynamic properties of the solution. A further interesting development of equation (i) is possible for a solution prepared using \(\mathrm{n}_{1}\) moles of solvent water and \(\mathrm{n}_{j}\) moles of solute. Thus
\[-\ln \left(\mathrm{x}_{1}\right)=\ln \left(\frac{1}{\mathrm{x}_{1}}\right)=\ln \left(\frac{\mathrm{n}_{1}+\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}\right)=\ln \left(1+\frac{\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}\right) \nonumber \]
But . \(\left(\mathrm{n}_{\mathrm{j}} / \mathrm{n}_{1}\right)<<1\). We expand the last term in equation (j).
\[\ln \left(1+\frac{\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}\right)=\frac{\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}-\frac{1}{2} \,\left(\frac{\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}\right)^{2}+\frac{1}{3} \,\left(\frac{\mathrm{n}_{\mathrm{j}}}{\mathrm{n}_{1}}\right)^{3}-\ldots . . \nonumber \]
If we retain only the first term;
\[\pi^{\mathrm{id}} \, \mathrm{V}_{1}^{*}[\ell ; \mathrm{T} ; \mathrm{p}]=\mathrm{R} \, \mathrm{T} \,\left(\mathrm{n}_{\mathrm{j}} / \mathrm{n}_{1}\right) \nonumber \]
But for a dilute solution, the volume of the solution \(\mathrm{V}\) is given by \(\mathbf{n}_{1} \, \mathrm{V}_{1}^{*}[\ell ; \mathrm{T} ; \mathrm{p}]\).
Or [2],
\[\pi^{\mathrm{id}} \, \mathrm{V}(\mathrm{aq})=\mathrm{n}_{\mathrm{j}} \, \mathrm{R} \, \mathrm{T} \nonumber \]
But concentration
\[\mathrm{c}_{\mathrm{j}}=\mathrm{n}_{\mathrm{j}} / \mathrm{V} \nonumber \]
Then [3]
\[\pi^{\mathrm{id}}=\mathrm{c}_{\mathrm{j}} \, \mathrm{R} \, \mathrm{T} \nonumber \]
Agreement between \(\pi(\mathrm{obs})\) and \(\pi^{\mathrm{id}}\) for aqueous solutions containing neutral solutes (e.g. sucrose) confirms the validity of the thermodynamic analysis.
Footnotes
[1] The term ‘semi-permeable’ in the present context means that the membrane is only permeable to the solvent. Perhaps the optimum semipermeable membrane is the vapor phase.
[2] Historically, equation(o) owes much to the equation of state for an ideal gas; i.e. \(\mathrm{p} \, \mathrm{V}=\mathrm{n} \, \mathrm{R} \, \mathrm{T}\). From an experimentally found proportionality between \(\pi\) and \(\mathrm{c}_{j}\), van’t Hoff showed that the proportionality constant can be approximated by \(\mathrm{R} \, \mathrm{T}\).
[3]
\[\pi=\left[\mathrm{mol} \mathrm{m}^{-3}\right] \,\left[\mathrm{J} \mathrm{K}^{-1} \mathrm{~mol}^{-1}\right] \,[\mathrm{K}]=\left[\mathrm{J} \mathrm{m}^{-3}\right]=\left[\mathrm{N} \mathrm{m} \mathrm{m}^{-3}\right]=\left[\mathrm{N} \mathrm{m}^{-2}\right] \nonumber \]


6: Guiding Behavior and Managing the Classroom
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Learning Objectives
At the end of the chapter, students should be able to:
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Identify factors that influence behavior
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Discuss the role of teachers in guiding behavior
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Explain influences on behavior
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Summarize principles of positive guidance
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Describe guidance strategies to use for children with disabilities
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Apply positive strategies to address behaviors
Social-emotional development is foundational to children’s learning in all other domains. Through children’s experiences in close relationships with parents and teachers, children develop and learn the social-emotional skills necessary to act and interact with self-confidence, regulate their behavior, and be successful in the early school years and beyond. With the guidance of responsive and caring adults, “young children develop an understanding of other people’s feelings and needs, are encouraged to feel empathy and caring, learn to manage their own behavior as responsible group members, and acquire a variety of other capabilities that will be directly related to their success in managing the classroom environment of kindergarten or the primary grades” (CDE 2008, 4).
[1]


1.2: How to download and install R
Since R is free, it is possible to download and install it without any additional procedures. There are several ways to do that depending on your operation system, but generally one need to google the uppercase letter “R” which will give the link to the site of R project. Next step is to find there “CRAN”, the on-line repository of all R -related software. In fact, there are multiple repositories (mirrors) so next step is to choose the nearest mirror. Then everything is straightforward, links will finally get you to the downloading page.
If your operating system has the package manager, software center of similar, installing R is even simpler. All that you need is to find R from within the manager and click install\(^{[1]}\).
It is also possible to install R and run it from iPhone, iPad and Android phones. However, it is recommended to have for R a full-featured computer since statistical calculations might consume plenty of resources.
Under Windows , R might be installed in two different modes, “one big window with smaller windows inside” ( MDI ) or “multiple independent windows” ( SDI ). We recommended to use the second (SDI) as R in other operating systems can work only in SDI mode. It is better to determine the mode during the installation: to make this choice, choose “Custom installation” from the one of first screens. If for some reason, you skipped it, it may be done later, through the menu ( R GUI options ).
On macOS , in addition to the core R , it is recommended to install also XQuartz software.
Apart from “graphical” R , both Windows and macOS have terminal R applications. While the functionality of Windows terminal programs is limited, on macOS it runs in a way similar to Linux and therefore makes the appropriate alternative. There are useful features in macOS graphical R , but also restrictions, especially with saving history of commands (see below). To start using this terminal R application in macOS , user should run any available terminal (like Terminal.app ) first.
References
1. If you do not use these managers or centers, it is recommended to regularly update your R, at least once a year.


Now we turn our attention to prenatal development which is divided into three periods: The germinal period, the embryonic period, and the fetal period. The following is an overview of some of the changes that take place during each period.
The Germinal Period
The
germinal period
(about 14 days in length) lasts from
conception
to implantation of the fertilized egg in the lining of the uterus. At ejaculation, millions of sperm are released into the vagina, but only a few reach the egg and typically only one fertilizes the egg. Once a single sperm has entered the wall of the egg, the wall becomes hard and prevents other sperm from entering. After the sperm has entered the egg, the tail of the sperm breaks off and the head of the sperm, containing the genetic information from the father, unites with the nucleus of the egg. It is typically fertilized in the top section of the fallopian tube and continues its journey to the uterus. As a result, a new cell is formed. This cell, containing the combined genetic information from both parents, is referred to as a
zygote
.
During this time, the organism begins cell division through mitosis. After five days of mitosis, there are 100 cells, which is now called a blastocyst. The blastocyst consists of both an inner and an outer group of cells. The inner group of cells, or embryonic disk will become the embryo, while the outer group of cells, or trophoblast, becomes the support system that nourishes the developing organism. This stage ends when the blastocyst fully implants into the uterine wall (U.S. National Library of Medicine, 2015).
Mitosis is a fragile process and fewer than one half of all zygotes survive beyond the first two weeks (Hall, 2004). Some of the reasons for this include: the egg and sperm do not join properly, thus their genetic material does not combine, there is too little or damaged genetic material, the zygote does not replicate, or the blastocyst does not implant into the uterine wall. The failure rate is higher for in vitro conceptions. The figure below illustrates the journey of the ova from its release to its fertilization, cell duplication, and implantation into the uterine lining. 22
The Embryonic Period
Starting the third week, the blastocyst has implanted in the uterine wall. Upon implantation this multi-cellular organism is called an
embryo
. Now blood vessels grow forming the placenta. The
placenta
is a structure connected to the uterus that provides nourishment and oxygen from the mother to the developing embryo via the umbilical cord.
During this period, cells continue to
differentiate
. Growth during prenatal development occurs in two major directions: from head to tail called
cephalocaudal development
and from the midline outward referred to as
proximodistal development
. This means that those structures nearest the head develop before those nearest the feet and those structures nearest the torso develop before those away from the center of the body (such as hands and fingers). You will see that this pattern continues after birth.
The head develops in the fourth week and the precursor to the heart begins to pulse. In the early stages of the embryonic period, gills and a tail are apparent. However, by the end of this stage they disappear and the organism takes on a more human appearance.
About 20 percent of organisms fail during the embryonic period, usually due to gross chromosomal abnormalities, often before the mother even knows that she is pregnant. It is during this stage that the major structures of the body are taking form, making the embryonic period the time when the organism is most vulnerable to the greatest amount of damage if exposed to harmful substances. Prospective mothers are not often aware of the risks they introduce to the developing embryo during this time. The embryo is approximately 1 inch in length and weighs about 4 grams at the end of eight weeks. The embryo can move and respond to touch at this time. 24
The Fetal Period
From the ninth week until birth (which is forty weeks for a full-term pregnancy), the organism is referred to as a
fetus
. During this stage, the major structures are continuing to develop. By the third month, the fetus has all its body parts including external genitalia. The fetus is about 3 inches long and weighs about 28 grams. In the following weeks, the fetus will develop hair, nails, teeth and the excretory and digestive systems will continue to develop.
During the 4th th months, the eyes become more sensitive to light and hearing develops. The respiratory system continues to develop, and reflexes such as sucking, swallowing and hiccupping, develop during the 5th month. Cycles of sleep and wakefulness are present at this time as well. The first chance of survival outside the womb, known as the age of viability is reached at about 24 weeks (Morgan, Goldenberg, & Schulkin, 2008). Many practitioners hesitate to resuscitate before 24 weeks. The majority of the neurons in the brain have developed by 24 weeks, although they are still rudimentary, and the glial or nurse cells that support neurons continue to grow. At 24 weeks the fetus can feel pain (Royal College of Obstetricians and Gynecologists, 1997).
Between the 7th - 9th months, the fetus is primarily preparing for birth. It is exercising its muscles and its lungs begin to expand and contract. The fetus gains about 5 pounds and 7 inches during this last trimester of pregnancy, and during the 8th month, a layer of fat develops under the skin. This layer of fat serves as insulation and helps the baby regulate body temperature after birth.
At around 36 weeks the fetus is almost ready for birth. It weighs about 6 pounds and is about 18.5 inches long. By week 37 all of the fetus’s organ systems are developed enough that it could survive outside the mother’s uterus without many of the risks associated with premature birth. The fetus continues to gain weight and grow in length until approximately 40 weeks. By then the fetus has very little room to move around and birth becomes imminent. The progression through the stages is shown in the following figure. 26
Monozygotic and Dizygotic Twins
Monozygotic
or identical twins occur when a fertilized egg splits apart in the first two weeks of development. The result is the creation of two separate, but genetically identical offspring. That is, they possess the same genotype and often the same phenotype. About one-third of twins are monozygotic twins.
Sometimes, however, two eggs or ova are released and fertilized by two separate sperm. The result is
dizygotic
or fraternal twins. These two individuals share the same amount of genetic material as would any two children from the same mother and father. In other words, they possess a different genotype and phenotype.
Older mothers are more likely to have dizygotic twins than are younger mothers, and couples who use fertility drugs are also more likely to give birth to dizygotic twins. 28
Teratogens
Good prenatal care is essential to protect against maternal and fetal/infant mortality and birth complications. The embryo and fetus is most at risk for some of the most severe problems during the first three months of development. Unfortunately, this is a time at which many mothers are unaware that they are pregnant. Today, we know many of the factors that can jeopardize the health of the developing child. The study of factors that contribute to birth defects is called teratology.
Teratogens
are environmental factors that can contribute to birth defects, and include some maternal diseases, pollutants, drugs and alcohol.
Factors influencing prenatal risks: There are several considerations in determining the type and amount of damage that might result from exposure to a particular teratogen (Berger, 2005). These include:
The timing of the exposure:
Structures in the body are vulnerable to the most severe damage when they are forming. If a substance is introduced during a particular structure's critical period (time of development), the damage to that structure may be greater. For example, the ears and arms reach their critical periods at about 6 weeks after conception. If a mother exposes the embryo to certain substances during this period, the arms and ears may be malformed. (see figure below)
The amount of exposure:
Some substances are not harmful unless the amounts reach a certain level. The critical level depends in part on the size and metabolism of the mother.
The number of teratogens:
Fetuses exposed to multiple teratogens typically have more problems than those exposed to only one.
Genetics:
Genetic makeup also plays a role on the impact a particular teratogen might have on the child. This is suggested by fraternal twins exposed to the same prenatal environment, but they do not experience the same teratogenic effects. The genetic makeup of the mother can also have an effect; some mothers may be more resistant to teratogenic effects than others.
Being male or female:
Males are more likely to experience damage due to teratogens than are females. It is believed that the Y chromosome, which contains fewer genes than the X, may have an impact. 31
There are four categories of teratogens:
Physical teratogens:
These could be saunas, hot tubs, or infections that raise a pregnant woman's body temperature to 102 degrees Fahrenheit or higher. This is associated with neural tube defects, spontaneous abortions, and various cardiovascular abnormalities.
Metabolic conditions affecting pregnant females:
Metabolic conditions are abnormalities in the chemical process of producing energy from food, and thereby affect the development and function of the body. If a pregnant woman is malnourished, then her fetus likely lacks the nutrients essential for its development. These include: malnutrition, diabetes, and thyroid disorders.
Infections:
Different maternal infections, including rubella virus, herpes simplex virus, and syphilis can cause congenital abnormalities in fetuses.
Drugs and chemicals:
When pregnant females ingest or absorb these, they may cause a variety of different effects based on specific agent, amount of exposure, and timing. This category includes: radiation, heavy metals (including lead), insecticides and herbicides, prescription and over the counter drugs, illicit and recreational drugs, alcohol, cigarettes, nicotine, caffeine, and even some vitamins. 33
While there are many, many potential teratogens, the following tables look at the effects of some different types of teratogens. The risks of exposure vary based on lifestyle and health. The effects may vary greatly depending on the factors mentioned previously. Protection and prevention will vary based on the method of exposure.
Table \(\PageIndex{1}\): Drugs as Teratogens
Teratogen
Potential Effects
Caffeine
Moderate amounts of caffeine (200 mg or around 12 ounces of coffee) appear to be safe during pregnancy. Some studies have shown a link between higher amounts of caffeine and miscarriage and preterm birth.34
Tobacco
Tobacco use has been associated with low birth weight, placenta previa, preterm delivery, fetal growth restriction, sudden infant death syndrome, cleft lip or palate, and later health problems (such as high blood pressure and diabetes). 35
Alcohol
There is no safe amount of alcohol a woman can drink while pregnant. Alcohol can slow down the baby's growth, affect the baby's brain, and cause birth defects, and may results in fetal alcohol spectrum disorder (FASD). The effects can be mild to severe. Children born with a severe form of FASD can have abnormal facial features, severe learning disabilities, behavioral problems, and other problems.36
Cocaine
Cocaine use has connected with low birth weight, stillbirths, spontaneous abortion, placental abruption, premature birth, miscarriage, and neonatal abstinence syndrome (fetal addiction leads the newborn to experiences withdrawal).37
Marijuana
No amount of marijuana has been proven safe to use during pregnancy. Heavy use has been associated with brain damage, premature birth, and stillbirth.38
Heroin
Using heroin during pregnancy can cause birth defects, placental abruption, premature birth, low birthweight, neonatal abstinence syndrome, still birth, and sudden infant death syndrome.39
Over-the-Counter (OTC) medication
Some OTC medications are safe to use during pregnancy and others may cause health problems during pregnancy. Pregnant women should consult their health care provider before using OTC medications.40
Prescription drugs
Some prescription drugs can cause birth defects that change the shape or function of one or more parts of the body that can affect overall health. Pregnant women should consult their health care provider before discontinuing or starting new medications.41
Herbal or dietary supplements
Except for some vitamins, little is known about using herbal or dietary supplements while pregnant. Most often there are no good studies to show if the herb can cause harm to you or your baby. Also, some herbs that are safe when used in small amounts as food might be harmful when used in large amounts as medicines.42
Table \(\PageIndex{2}\): Environmental Teratogens
Teratogen
Potential Effects
Lead
Exposure to high levels of lead before and during pregnancy can lead to high blood pressure, problems with fetal brain and nervous system development, premature birth, low birthweight, and miscarriage.43
Mercury
Exposure to mercury in the womb can cause brain damage and hearing and vision problems.44
Radiation
Exposure to radiation during pregnancy (especially between 2 and 18 weeks of pregnancy) can slow growth, cause birth defects, affect brain development, cause cancer, and cause miscarriage.45
Solvents
These chemicals include degreasers, paint thinners, stain and varnish removers, paints, and more Maternal inhalation of solvents can cause fetal exposure than may cause miscarriage, slow fetal growth, premature birth, and birth defects.46
Table \(\PageIndex{3}\): Maternal Infections as Teratogens
Teratogen
Potential Effects
Rubella
Congenital infection (becoming infected while in the womb) can damage the development of the eyes, ears, heart, and brain and result in deafness.47
Zika
Congenital infection can cause microcephaly and other severe brain abnormalities. 48
Varicella (chicken pox)
Congenital infection can cause a severe form of the infection affecting the eyes, limbs, skin, and central nervous system.49
Sexually transmitted infections
Infections such as HIV, gonorrhea, syphilis, and chlamydia can be passed from the mother during pregnancy and/or delivery.50
Listeria
Pregnant women are more susceptible to this food-borne illness. Congenital infection can cause miscarriage, stillbirth, premature labor, and neonatal sepsis. 51
Table \(\PageIndex{4}\): Teratogens from Animals/Pets
Teratogen
Potential Effects
Toxoplamosis
This parasite can be passed through cat feces and undercooked meat (especially pork, lamb, or deer meet). If the fetus is infected it can cause miscarriage, stillbirth, hydrocephalus, macro or microcephalus, vision issues, and damage to the nervous system.52
Lymphocytic choriomeningitis
This virus carried by rodents including mice, hamsters, and guinea pigs. If an infected mother passes it to her fetus it can cause issues with brain development, long-term neurological and/or visual impairment, and higher mortality rates after birth.53
Maternal Factors
There are additional factors that affect the outcome of pregnancy for both mother and child. Let’s look at these next.
Mothers over 35
Most women over 35 who become pregnant are in good health and have healthy pregnancies. However, according to the March of Dimes (2016d), women over age 35 are more likely to have an increased risk of:
Fertility problems
High blood pressure
Diabetes
Miscarriages
Placenta Previa
Cesarean section
Premature birth
Stillbirth
A baby with a genetic disorder or other birth defects
Because a woman is born with all her eggs, environmental teratogens can affect the quality of the eggs as women get older. Also, a woman’s reproductive system ages which can adversely affect the pregnancy. Some women over 35 choose special prenatal screening tests, such as a maternal blood screening, to determine if there are any health risks for the baby.
Although there are medical concerns associated with having a child later in life, there are also many positive consequences to being a more mature parent. Older parents are more confident, less stressed, and typically married, providing family stability. Their children perform better on math and reading tests, and they are less prone to injuries or emotional troubles (Albert, 2013). Women who choose to wait are often well educated and lead healthy lives. According to Gregory (2007), older women are more stable, demonstrate a stronger family focus, possess greater self-confidence, and have more money. Having a child later in one’s career equals overall higher wages. In fact, for every year a woman delays motherhood, she makes 9% more in lifetime earnings. Lastly, women who delay having children actually live longer.
Teenage Pregnancy
A teenage mother is at a greater risk for having pregnancy complications including anemia, and high blood pressure. These risks are even greater for those under age 15. Infants born to teenage mothers have a higher risk for being premature and having low birthweight or other serious health problems. Premature and low birthweight babies may have organs that are not fully developed which can result in breathing problems, bleeding in the brain, vision loss, serious intestinal problems, and higher likelihood of dying. Reasons for these health issues include that teenagers are the least likely of all age groups to get early and regular prenatal care and they may engage in negative behaviors including eating unhealthy food, smoking, drinking alcohol, and taking drugs.
Gestational Diabetes
Seven percent of pregnant women develop
gestational diabetes
(March of Dimes, 2015b). Diabetes is a condition where the body has too much glucose in the bloodstream.
Most pregnant women have their glucose level tested between 24 to 28 weeks of pregnancy. Gestational diabetes usually goes away after the mother gives birth, but it might indicate a risk for developing diabetes later in life. If untreated, gestational diabetes can cause premature birth, stillbirth, the baby having breathing problems at birth, jaundice, or low blood sugar. Babies born to mothers with gestational diabetes can also be considerably heavier (more than 9 pounds) making the labor and birth process more difficult. For expectant mothers, untreated gestational diabetes can cause preeclampsia (high blood pressure and signs that the liver and kidneys may not be working properly) discussed later in the chapter.
Risk factors for gestational diabetes include age (being over age 25), being overweight or gaining too much weight during pregnancy, family history of diabetes, having had gestational diabetes with a prior pregnancy, and race and ethnicity (African-American, Native American, Hispanic, Asian, or Pacific Islander have a higher risk). Eating healthy and maintaining a healthy weight during pregnancy can reduce the chance of gestational diabetes. Women who already have diabetes and become pregnant need to attend all their prenatal care visits, and follow the same advice as those for women with gestational diabetes as the risk of preeclampsia, premature birth, birth defects, and stillbirth are the same.
High Blood Pressure (Hypertension)
Hypertension is a condition in which the pressure against the wall of the arteries becomes too high. There are two types of high blood pressure during pregnancy, gestational and chronic. Gestational hypertension only occurs during pregnancy and goes away after birth. Chronic high blood pressure refers to women who already had hypertension before the pregnancy or to those who developed it during pregnancy and it did not go away after birth.
According to the March of Dimes (2015c), about 8 in every 100 pregnant women have high blood pressure. High blood pressure during pregnancy can cause premature birth and low birth weight (under five and a half pounds), placental abruption, and mothers can develop preeclampsia.
Rh Disease
Rh is a protein found in the blood. Most people are Rh positive, meaning they have this protein. Some people are Rh negative, meaning this protein is absent. Mothers who are Rh negative are at risk of having a baby with a form of anemia called Rh disease (March of Dimes, 2009). A father who is Rh-positive and mother who is Rh-negative can conceive a baby who is Rh-positive. Some of the fetus’s blood cells may get into the mother’s bloodstream and her immune system is unable to recognize the Rh factor.
The immune system starts to produce antibodies to fight off what it thinks is a foreign invader. Once her body produces immunity, the antibodies can cross the placenta and start to destroy the red blood cells of the developing fetus. As this process takes time, often the first Rh positive baby is not harmed, but as the mother’s body will continue to produce antibodies to the Rh factor across her lifetime, subsequent pregnancies can pose greater risk for an Rh positive baby. In the newborn, Rh disease can lead to jaundice, anemia, heart failure, brain damage and death.
Weight Gain during Pregnancy
According to March of Dimes (2016f), during pregnancy most women need only an additional 300 calories per day to aid in the growth of the fetus. Gaining too little or too much weight during pregnancy can be harmful. Women who gain too little may have a baby who is low-birth weight, while those who gain too much are likely to have a premature or large baby. There is also a greater risk for the mother developing preeclampsia and diabetes, which can cause further problems during the pregnancy.
The table below shows the healthy weight gain during pregnancy. Putting on the weight slowly is best. Mothers who are concerned about their weight gain should talk to their health care provider.
Table \(\PageIndex{5}\): Weight Gain during Pregnancy
If you were a healthy weight before pregnancy:
If you were underweight before pregnancy:
If you were overweight before pregnancy:
If you were obese before pregnancy:
Gain 25-35 pounds
1-41⁄2 pounds in the 1st trimester
1 pound per week in the 2nd and 3rd trimesters
Gain 28-30 pounds
1-41⁄2 pounds in the 1st trimester
A little more than 1 pound per week thereafter
Gain 12-25 pounds
1-41⁄2 pounds in the 1st trimester
A little more than 1⁄2 pound per week in 2nd and 3rd trimesters
11-20 pounds
1-41⁄2 pounds in the 1st trimester
A little more than 1⁄2 pound per week in 2nd and 3rd trimesters
Mothers of twins or higher order multiples need to gain more in each category.
Stress
Feeling stressed is common during pregnancy, but high levels of stress can cause complications including having a premature baby or a low-birthweight baby. Babies born early or too small are at an increased risk for health problems. Stress-related hormones may cause these complications by affecting a woman’s immune systems resulting in an infection and premature birth. Additionally, some women deal with stress by smoking, drinking alcohol, or taking drugs, which can lead to problems in the pregnancy. High levels of stress in pregnancy have also been correlated with problems in the baby’s brain development and immune system functioning, as well as childhood problems such as trouble paying attention and being afraid (March of Dimes, 2012b).
Depression
Depression is a significant medical condition in which feelings of sadness, worthlessness, guilt, and fatigue interfere with one’s daily functioning. Depression can occur before, during, or after pregnancy, and 1 in 7 women are treated for depression sometime between the year before pregnancy and year after pregnancy (March of Dimes, 2015a). Women who have experienced depression previously are more likely to have depression during pregnancy. Consequences of depression include the baby being born premature, having a low birthweight, being more irritable, less active, less attentive, and having fewer facial expressions.
About 13% of pregnant women take an antidepressant during pregnancy. It is important that women taking antidepressants during pregnancy discuss the medication with a health care provider as some medications can cause harm to the developing organism.
Paternal Impact
The age of fathers at the time of conception is also an important factor in health risks for children. According to Nippoldt (2015), offspring of men over 40 faces an increased risk of miscarriages, autism, birth defects, achondroplasia (bone growth disorder) and schizophrenia. These increased health risks are thought to be due to accumulated chromosomal aberrations and mutations during the maturation of sperm cells in older men (Bray, Gunnell, & Smith, 2006). However, like older women, the overall risks are small.
In addition, men are more likely than women to work in occupations where hazardous chemicals, many of which have teratogenic effects or may cause genetic mutations, are used (Cordier, 2008). These may include petrochemicals, lead, and pesticides that can cause normal sperm and lead to miscarriages or diseases. Men are also more likely to be a source of second hand smoke for their developing offspring. As noted earlier, smoking by either the mother or around the mother can hinder prenatal development. 57
Prenatal Assessment
A number of assessments are suggested to women as part of their routine prenatal care to find conditions that may increase the risk of complications for the mother and fetus (Eisenberg, Murkoff, & Hathaway, 1996). These can include blood and urine analyses and screening and diagnostic tests for birth defects.
Ultrasound is one of the main screening tests done in combination with blood tests. The ultrasound is a test in which sound waves are used to examine the fetus. There are two general types. Transvaginal ultrasounds are used in early pregnancy, while transabdominal ultrasounds are more common and used after 10 weeks of pregnancy (typically, 16 to 20 weeks).
Ultrasounds are used to check the fetus for defects or problems. It can also find out the age of the fetus, location of the placenta, fetal position, movement, breathing and heart rate, amount of amniotic fluid in the uterus, and number of fetuses. Most women have at least one ultrasound during pregnancy, but if problems are noted, additional ultrasounds may be recommended.
When diagnosis of a birth defect is necessary, ultrasounds help guide the more invasive diagnostic tests of amniocentesis and chorionic villus sampling.
Amniocentesis
is a procedure in which a needle is used to withdraw a small amount of amniotic fluid and cells from the sac surrounding the fetus and later tested.
Chorionic Villus Sampling
is a procedure in which a small sample of cells is taken from the placenta and tested. Both amniocentesis and chorionic villus sampling have a risk of miscarriage, and consequently, they are not done routinely. 61
Complications of Pregnancy
There are a number of common side effects of pregnancy. Not everyone experiences all of these, nor to the same degree. And although they are considered "minor", this is not to say that these problems are not potentially very uncomfortable. These side effects include nausea (particularly during the first 3-4 months of pregnancy as a result of higher levels of estrogen in the system), heartburn, gas, hemorrhoids, backache, leg cramps, insomnia, constipation, shortness of breath or varicose veins (as a result of carrying a heavy load on the abdomen). These are minor issues.
But there are also serious complications of pregnancy which can pose health risks to mother and child and that often require hospitalization.
Hyperemesis gravidarum
is characterized by severe nausea, vomiting, weight loss, and possibly dehydration. Signs and symptoms may also include vomiting many times a day and feeling faint. The exact causes of hyperemesis gravidarum are unknown. Risk factors include the first pregnancy, multiple pregnancy, obesity, prior or family history of HG, trophoblastic disorder, and a history of eating disorders. Treatment includes drinking fluids and a bland diet. Medication, intravenous fluids, and hospitalization may be required. Hyperemesis gravidarum is estimated to affect 0.3–2.0% of pregnant women. Those affected have a low risk of miscarriage but a higher risk of premature birth.
Ectopic Pregnancy
occurs when the zygote becomes attached to the fallopian tube before reaching the uterus. About 1 in 50 pregnancies in the United States are tubal pregnancies and this number has been increasing because of the higher rates of pelvic inflammatory disease and Chlamydia (Carroll, 2007). Abdominal pain, vaginal bleeding, nausea and fainting are symptoms of ectopic pregnancy.
Spontaneous abortion
is experienced in an estimated 20-40 percent of undiagnosed pregnancies and in another 10 percent of diagnosed pregnancies. Usually the body aborts due to chromosomal abnormalities, and this typically happens before the 12th week of pregnancy. Cramping and bleeding result and normal periods return after several months. Some women are more likely to have repeated miscarriages due to chromosomal, amniotic, or hormonal problems, but miscarriage can also be a result of defective sperm (Carrell et. al., 2003).
Preeclampsia
, also known as
Toxemia
, is characterized by a sharp rise in blood pressure, a leakage of protein into the urine as a result of kidney problems, and swelling of the hands, feet, and face during the third trimester of pregnancy. Preeclampsia is the most common complication of pregnancy. When preeclampsia causes seizures, the condition is known as eclampsia, which is the second leading cause of maternal death in the United States. Preeclampsia is also a leading cause of fetal complications, which include low birth weight, premature birth, and stillbirth. Treatment is typically bed rest and sometimes medication. If this treatment is ineffective, labor may be induced.
Maternal Mortality
: Approximately 1000 women die in childbirth around the world each day (World Health Organization, 2010). Rates are highest in Sub-Saharan Africa and South Asia, although there has been a substantial decrease in these rates. The campaign to make childbirth safe for everyone has led to the development of clinics accessible to those living in more isolated areas and training more midwives to assist in childbirth.63
Infertility and Building Families
Infertility
When a couple has failed to conceive a child in a year, they receive the diagnosis of infertility. Infertility affects about 10 to 15 percent of couples in the United States (Mayo Clinic, 2015). Male factors create infertility in about a third of the cases. For men, the most common cause is a lack of sperm production or low sperm production.
Female factors cause infertility in another third of cases. For women, one of the most common causes of infertility is the failure to ovulate. Another cause of infertility in women is Pelvic Inflammatory Disease (PID), which is an infection of a woman’s reproductive organs (Carroll, 2007).
Both male and female factors contribute to the remainder of cases of infertility. 64
Options for Building Families
There are numerous options to pursue parenthood and building families. Let’s briefly explore some of these.
Assisted Reproductive Technology
Assisted reproductive technology (ART) is the technology used to achieve pregnancy in procedures such as fertility medication (to stimulate ovulation), surgical procedures, artificial insemination IUI), in vitro fertilization (IVF) and surrogacy. These options are available for people who are experiencing infertility or cannot conceive children naturally (which also includes single parents, and gay/lesbian couples). 65
Intrauterine insemination
:
(IUI) as a type of artificial insemination involves the placement of sperm directly into the uterus at the time of ovulation, either in a natural menstrual cycle or following ovarian stimulation. 66
In vitro fertilization (IVF):
IVF generally starts with stimulating the ovaries to increase egg production. Most fertility medications are agents that stimulate the development of follicles in the ovary. Examples are gonadotropins and gonadotropin releasing hormone. After stimulation, the physician surgically extracts one or more eggs from the ovary, and unites them with sperm in a laboratory setting, with the intent of producing one or more embryos. Fertilization takes place outside the body, and the fertilized egg is reinserted into the woman's reproductive tract, in a procedure called embryo transfer. 67
Donor Gametes & Embryos:
People can also use sperm, ova (eggs), and embryos from donors in conjunction with ART. These donations take place through agencies and donor banks or between private individuals. In the U.S., donors can be compensated for their donations.
Surrogacy:
In surrogacy, one woman (surrogate mother) carries a child for another person/s (commissioning person/couple), based on a legal agreement before conception requiring the child to be relinquished to the commissioning person/couple following birth. There are different types of surrogacy which relate to whether or not the ova used to conceive the child are her own (
traditional surrogacy
) or not (
gestational surrogacy
). 69
Adoption:
People can also choose to pursue
adoption
to build their families (with or without experiencing infertility). Adoption can take place through the foster care system, privately, or through agencies. Adoptions can be domestic (within the U.S.) or international. And they can be open (with differing amounts of contact between biological/birth families and adoptive families) or closed.
48. Protocols on prenatal care for pregnant women with Zika infection and children with microcephaly: nutritional approach by Rachel de Sá Barreto Luna Callou Cruz, Malaquias Batista Filho, Maria de Fátima Costa Caminha, and Edvaldo da Silva Souza is licensed under
CC BY 4.0


1.2: Introduction to Habits for Success
What you’ll learn to do: identify common habits that lead to success in college
People go to college for a range of different reasons, and so college success means different things for different people. Traditionally, college was a place some young adults went after high school to explore courses and majors before settling into a job path. According to a 2015 UCLA survey [1] , most people currently go to college for one or more of 7 main reasons
- To be able to get a better job
- To gain a general education and appreciation of ideas
- To become a more cultured person
- To be able to make more money
- To learn more about things that interest me
- To get training for a specific career
- To prepare for graduate or professional school
Take a moment to think about the reasons you are here:
- Why college? Why now?
- How do you define success in college?
- What do you imagine college life to be like?
- Do you think you are ready for college? Why or why not?
- What have you done to prepare for college?
- What do you think college professors expect from students?
- What do you think going to college means for your future?
Regardless of your personal goals and expectations, doing well in college means learning new behaviors and understanding a new culture. Professors and college administrators, for example, will expect you to behave in certain ways, often without any explicit instructions on their part. Professors will expect you to spend several hours a week working on class concepts (homework, writing, preparing for exams) on your own time. They will not tell you WHEN to spend those hours, but leave it up to you to recognize the need to put in the effort and schedule the time accordingly.
In this section, we examine the strategies you can employ to understand the expectations of college and achieve success in your endeavors.
- Kevin Eagan et al., The American Freshman: National Norms Fall 2015 (Los Angeles: Higher Education Research Institute, UCLA, 2015) ↵
Contributors and Attributions
- Introduction to Habits for Success. Provided by : Lumen Learning. License : CC BY: Attribution
- What's College For. Authored by : Alise Lamoreaux, Dave Dillon. Provided by : Rebus Community. Located at : https://press.rebus.community/blueprint1/chapter/2-whats-college-for/ . Project : Blueprint for Success in College: Indispensable Study Skills and Time Management Strategies. License : CC BY: Attribution
- Image of graduates. Authored by : Nottingham Trent University. Located at : https://flic.kr/p/a9W8ku . License : CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives


3.3: Vector Addition and Subtraction- Analytical Methods
Learning Objectives
By the end of this section, you will be able to:
- Understand the rules of vector addition and subtraction using analytical methods.
- Apply analytical methods to determine vertical and horizontal component vectors.
- Apply analytical methods to determine the magnitude and direction of a resultant vector.
Analytical methods of vector addition and subtraction employ geometry and simple trigonometry rather than the ruler and protractor of graphical methods. Part of the graphical technique is retained, because vectors are still represented by arrows for easy visualization. However, analytical methods are more concise, accurate, and precise than graphical methods, which are limited by the accuracy with which a drawing can be made. Analytical methods are limited only by the accuracy and precision with which physical quantities are known.
Resolving a Vector into Perpendicular Components
Analytical techniques and right triangles go hand-in-hand in physics because (among other things) motions along perpendicular directions are independent. We very often need to separate a vector into perpendicular components. For example, given a vector like \(\displaystyle A\) in Figure \(\PageIndex{1}\), we may wish to find which two perpendicular vectors, \(\displaystyle A_x\) and \(\displaystyle A_y\), add to produce it.
\(\displaystyle A_x\) and \(\displaystyle A_y\) are defined to be the components of \(\displaystyle A\) along the x- and y-axes. The three vectors \(\displaystyle A, A_x\), and \(\displaystyle A_y\) form a right triangle:
\[\displaystyle A_x + A_y = A.\]
Note that this relationship between vector components and the resultant vector holds only for vector quantities (which include both magnitude and direction). The relationship does not apply for the magnitudes alone. For example, if \(\displaystyle A_x=3 m\) east, \(\displaystyle A_y=4 m\) north, and \(\displaystyle A=5 m \)north-east, then it is true that the vectors \(\displaystyle A_x + A_y = A\). However, it is not true that the sum of the magnitudes of the vectors is also equal. That is,
\[\displaystyle 3 m+4 m ≠ 5 m\]
Thus,
\[\displaystyle A_x+A_y≠A\]
If the vector \(\displaystyle A\) is known, then its magnitude \(\displaystyle A\) (its length) and its angle \(\displaystyle θ\) (its direction) are known. To find \(\displaystyle A_x\) and \(\displaystyle A_y\), its x- and y-components, we use the following relationships for a right triangle.
\[\displaystyle A_x=Acosθ\]
and
\[\displaystyle A_y=Asinθ.\]
Suppose, for example, that A is the vector representing the total displacement of the person walking in a city considered in Kinematics in Two Dimensions: An Introduction and Vector Addition and Subtraction: Graphical Methods.
Then \(\displaystyle A=10.3\) blocks and \(\displaystyle θ=29.1º\), so that
\[\displaystyle A_x=A\cos θ=(10.3 blocks)(\cos 29.1º)=9.0 \quad blocks \]
\[\displaystyle A_y=A\sin θ=(10.3 blocks)(\sin 29.1º)=5.0 \quad blocks \]
Calculating a Resultant Vector
If the perpendicular components \(\displaystyle A_x\) and \(\displaystyle A_y\) of a vector \(\displaystyle A\) are known, then A can also be found analytically. To find the magnitude \(\displaystyle A\) and direction \(\displaystyle θ\) of a vector from its perpendicular components \(\displaystyle A_x\) and \(\displaystyle A_y\), we use the following relationships:
\[\displaystyle A=\sqrt{A_{x^2}+A_{y^2}}\]
\[\displaystyle θ=tan^{−1}(A_y/A_x)\]
Note that the equation \(\displaystyle A=\sqrt{A^2_x+A^2_y}\) is just the Pythagorean theorem relating the legs of a right triangle to the length of the hypotenuse. For example, if \(\displaystyle A_x\) and \(\displaystyle A_y\) are 9 and 5 blocks, respectively, then \(\displaystyle A=\sqrt{9^2+5^2}=10.3\) blocks, again consistent with the example of the person walking in a city. Finally, the direction is \(\displaystyle θ=tan^{–1}(5/9)=29.1º\), as before.
DETERMINING VECTORS AND VECTOR COMPONENTS WITH ANALYTICAL METHODS
Equations \(\displaystyle A_x=Acosθ\) and \(\displaystyle A_y=Asinθ\) are used to find the perpendicular components of a vector—that is, to go from \(\displaystyle A\) and \(\displaystyle θ\) to \(\displaystyle A_x\) and \(\displaystyle A_y\). Equations \(\displaystyle A=\sqrt{A^2_x+A^2_y}\) and \(\displaystyle θ=tan^{–1}(A_y/A_x)\) are used to find a vector from its perpendicular components—that is, to go from \(\displaystyle A_x\) and \(\displaystyle A_y\) to \(\displaystyle A\) and \(\displaystyle θ\). Both processes are crucial to analytical methods of vector addition and subtraction.
Adding Vectors Using Analytical Methods
To see how to add vectors using perpendicular components, consider Figure \(\PageIndex{5}\), in which the vectors \(\displaystyle A\) and \(\displaystyle B\) are added to produce the resultant \(\displaystyle R\).
If \(\displaystyle A\) and \(\displaystyle B\) represent two legs of a walk (two displacements), then \(\displaystyle R\) is the total displacement. The person taking the walk ends up at the tip of R. There are many ways to arrive at the same point. In particular, the person could have walked first in the x-direction and then in the y-direction. Those paths are the x- and y-components of the resultant, \(\displaystyle R_x\) and \(\displaystyle R_y\). If we know \(\displaystyle R_x\) and \(\displaystyle R_y\), we can find \(\displaystyle R\) and \(\displaystyle θ\) using the equations \(\displaystyle A=\sqrt{A_x^2+A_y^2}\) and \(\displaystyle θ=tan^{–1}(A_y/A_x)\). When you use the analytical method of vector addition, you can determine the components or the magnitude and direction of a vector.
Step 1. Identify the x- and y-axes that will be used in the problem. Then, find the components of each vector to be added along the chosen perpendicular axes. Use the equations \(\displaystyle A_x=Acosθ\) and \(\displaystyle A_y=Asinθ\) to find the components. In Figure, these components are \(\displaystyle A_x, A_y, B_x\), and \(\displaystyle B_y\). The angles that vectors \(\displaystyle A\) and \(\displaystyle B\) make with the x-axis are \(\displaystyle θ_A\) and \(\displaystyle θ_B\), respectively.
Step 2. Find the components of the resultant along each axis by adding the components of the individual vectors along that axis. That is, as shown in Figure \(\PageIndex{7}\ ,
\[\displaystyle R_x=A_x+B_x\]
and
\[\displaystyle R_y=A_y+B_y.\]
Components along the same axis, say the x -axis, are vectors along the same line and, thus, can be added to one another like ordinary numbers. The same is true for components along the y -axis. (For example, a 9-block eastward walk could be taken in two legs, the first 3 blocks east and the second 6 blocks east, for a total of 9, because they are along the same direction.) So resolving vectors into components along common axes makes it easier to add them. Now that the components of R are known, its magnitude and direction can be found.
Step 3. To get the magnitude \(\displaystyle R\) of the resultant, use the Pythagorean theorem:
\[\displaystyle R=\sqrt{R^2_x+R^2_y}\]
Step 4. To get the direction of the resultant:
\[\displaystyle θ=tan^{−1}(R_y/R_x)\]
The following example illustrates this technique for adding vectors using perpendicular components.
Example \(\displaystyle \PageIndex{1}\): Adding Vectors Using Analytical Methods
Add the vector \(\displaystyle A\) to the vector \(\displaystyle B\) shown in Figure, using perpendicular components along the x - and y- axes. The x - and y -axes are along the east–west and north–south directions, respectively. Vector \(\displaystyle A\) represents the first leg of a walk in which a person walks \(\displaystyle 53.0 m\) in a direction \(\displaystyle 20.0º\) north of east. Vector \(\displaystyle B\) represents the second leg, a displacement of \(\displaystyle 34.0 m\) in a direction \(\displaystyle 63.0º\) north of east.
Figure \(\PageIndex{8}\)
:
Vector \(\displaystyle A\) has magnitude \(\displaystyle 53.0 m\) and direction \(\displaystyle 20.0º\) north of the
x
-axis. Vector B has magnitude \(\displaystyle 34.0 m\) and direction \(\displaystyle 63.0º\) north of the x-axis. You can use analytical methods to determine the magnitude and direction of \(\displaystyle R\).
Strategy
The components of \(\displaystyle A\) and \(\displaystyle B\) along the x- and y -axes represent walking due east and due north to get to the same ending point. Once found, they are combined to produce the resultant.
Solution
Following the method outlined above, we first find the components of \(\displaystyle A\) and \(\displaystyle B\) along the x- and y- axes. Note that \(\displaystyle A=53.0 m, θ_A=20.0º, B=34.0 m,\) and \(\displaystyle θ_B=63.0º\). We find the x- components by using \(\displaystyle A_x=Acosθ\), which gives
\[\displaystyle A_x=Acosθ_A=(53.0 m)(cos 20.0º)(53.0 m)(0.940)=49.8 m\]
and
\[\displaystyle B_x=Bcosθ_B=(34.0 m)(cos 63.0º)(34.0 m)(0.454)=15.4 m.\]
Similarly, the y- components are found using \(\displaystyle A_y=Asinθ_A\):
\[\displaystyle A_y=Asinθ_A=(53.0 m)(sin 20.0º)(53.0 m)(0.342)=18.1 m\]
and
\[\displaystyle B_y=Bsinθ_B=(34.0 m)(sin 63.0º)(34.0 m)(0.891)=30.3 m.\]
The x- and y- components of the resultant are thus
\[\displaystyle R_x=A_x+B_x=49.8 m+15.4 m=65.2 m\]
and
\[\displaystyle R_y=A_y+B_y=18.1 m+30.3 m=48.4 m.\]
Now we can find the magnitude of the resultant by using the Pythagorean theorem:
\[\displaystyle R=\sqrt{R^2_x+R^2_y}=\sqrt{(65.2)^2+(48.4)^2m}\]
so that
\[\displaystyle R=81.2 m.\]
Finally, we find the direction of the resultant:
\[\displaystyle θ=tan^{−1}(R_y/R_x)=+tan^{−1}(48.4/65.2).\]
Thus,
\[\displaystyle θ=tan^{−1}(0.742)=36.6º.\]
Discussion
This example illustrates the addition of vectors using perpendicular components. Vector subtraction using perpendicular components is very similar—it is just the addition of a negative vector.
Subtraction of vectors is accomplished by the addition of a negative vector. That is, \(\displaystyle A−B≡A+(–B)\). Thus, the method for the subtraction of vectors using perpendicular components is identical to that for addition. The components of \(\displaystyle –B\) are the negatives of the components of \(\displaystyle B\). The x- and y- components of the resultant \(\displaystyle A−B = R\) are thus
\[\displaystyle R_x=A_x+(–B_x)\]
and
\[\displaystyle R_y=A_y+(–B_y)\]
and the rest of the method outlined above is identical to that for addition. (See Figure \(\PageIndex{10}\).)
Analyzing vectors using perpendicular components is very useful in many areas of physics, because perpendicular quantities are often independent of one another. The next module, Projectile Motion, is one of many in which using perpendicular components helps make the picture clear and simplifies the physics.
PHET EXPLORATIONS: VECTOR ADDITION
Learn how to add vectors. Drag vectors onto a graph, change their length and angle, and sum them together. The magnitude, angle, and components of each vector can be displayed in several formats.
- The analytical method of vector addition and subtraction involves using the Pythagorean theorem and trigonometric identities to determine the magnitude and direction of a resultant vector.
- The steps to add vectors \(\displaystyle A\) and \(\displaystyle B\) using the analytical method are as follows:
Step 1: Determine the coordinate system for the vectors. Then, determine the horizontal and vertical components of each vector using the equations
\(\displaystyle A_x=Acosθ\)
\(\displaystyle B_x=Bcosθ\)
and
\(\displaystyle A_y=Asinθ\)
\(\displaystyle B_y=Bsinθ.\)
Step 2: Add the horizontal and vertical components of each vector to determine the components Rx and Ry of the resultant vector, R:
\(\displaystyle R_x=A_x+B_x\)
and
\(\displaystyle R_y=A_y+B_y\).
Step 3: Use the Pythagorean theorem to determine the magnitude, R, of the resultant vector R:
\(\displaystyle R=\sqrt{R^2_x+R^2_y}\).
Step 4: Use a trigonometric identity to determine the direction, \(\displaystyle θ\), of R :
\(\displaystyle θ=tan^{−1}(R_y/R_x)\).
Glossary
- analytical method
- the method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities


2.17: The Stigma of Mental Illness
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Words can hurt. Many derogatory words and phrases are used in relation to mental illness. However, these words maintain the stereotyped image and not the reality about mental illness. Try not to use these words, and encourage students not to use them. It is more appropriate to refer to “a person who has a mental illness” when speaking about someone. “Mentally ill people are nuts, crazy, wacko.” “Mentally ill people are morally bad.” “Mentally ill people are dangerous and should be locked in an asylum forever.” “Mentally ill people need somebody to take care of them.” How often have we heard comments like these or seen these types of portrayals in movies, television shows, or books? We may even be guilty of making comments like them ourselves. Is there any truth behind these portrayals, or is that negative view based on our ignorance and fear?
Stigmas are negative stereotypes about groups of people.
- Individuals who have a mental illness are irresponsible and can’t make life decisions for themselves.
- People who have a mental illness are childlike and must be taken care of by parents or guardians.
- People who have a mental illness should just get over it.
Each of those preconceptions about people who have a mental illness is based on false information. Very few people who have a mental illness are dangerous to society. Most can hold jobs, attend school, and live independently. A person who has a mental illness cannot simply decide to get over it any more than someone who has a different chronic disease such as diabetes, asthma, or heart disease can. A mental illness, like those other diseases, is caused by a physical problem in the body.
   The stigmatizing attitudes toward mental illness held by both the public and those who have a mental illness lead to feelings of shame and guilt, loss of self-esteem, social dependence, and a sense of isolation and hopelessness. One of the worst consequences of stigma is that people who are struggling with a mental illness may be reluctant to seek treatment that, in most cases, would significantly relieve their symptoms.
Providing accurate information is one way to reduce stigmas about mental illness. Advocacy groups protest stereotypes imposed upon those who are mentally ill. They demand that the media stop presenting inaccurate views of mental illness and that the public stops believing these negative views. A powerful way of countering stereotypes about mental illness occurs when members of the public meet people who are effectively managing a serious mental illness: holding jobs, providing for themselves, and living as good neighbors in a community.


3.2: Reading- Operating Systems
Introduction
The PC of a business end-user will quite commonly provide a number of different application programs, but no program development tools. It is also possible (although unlikely) that the PC of a programmer could provide development tools only, and no other commercial applications. But the one thing that all these machines would definitely have is an operating system (OS). The operating system is an essential piece of software that resides on virtually every computer. It allows the computer to run a number of different applications apparently simultaneously, and shares resources such as printers between a number of different users, while at the same time performing those functions that are critical to the correct operating of the computer system, regardless of which application is running.
Different types of computers may require different operating systems. Most mainframe computers have a proprietary operating system, such as IBM’s MVS or Siemen’s BS2000. At the opposite end of the market, we find that the leading operating system for the IBM compatible Personal Computers is Microsoft Windows (having all but replaced its predecessor MS-DOS) although Mac-OS and Unix variants such as Linux also have strong followings.
Today’s operating systems are true marvels of engineering and rate among the most complex artifacts designed by humans. Their complexity stems from the increasing number of functions that an operating system is required to handle.
Multitasking
Today’s computers handle many applications at the same time: you could be downloading a file from the Internet at the same time as you update a spreadsheet that is embedded within a word-processing document (while at the same time your virus scanner is running in the background). Each application needs to share the CPU, main memory and all peripheral devices. The OS sees to it that all conflicts are resolved and each application gets a fair share of the common resources, often in accordance with a certain priority schedule. An important task, therefore, is that of the proper scheduling of different tasks. The OS also ensures that illbehaving applications do not impact on the integrity of the other applications and their data. (By the way, when a single application program runs multiple tasks simultaneously, this is known as multithreading.)
Multi-user management
Barring the personal computer, computers have more than a single user at any one time – a typical mainframe may have to handle many thousands of simultaneous users. Each of the users may operate a different application (see multitasking) but will not be prepared to wait for other users to finish their tasks. So the OS sees to it that each user gets a fair share of the CPU of the mainframe, by slicing each second in tiny fractions and allocating them to the different users. In addition, each user may have a different profile in terms of access to certain peripheral devices and data. This requires sophisticated security and data management.
Memory management
Apart from the CPU, primary memory is often the most expensive and scarcest component of a computer system. Efficient memory management is a key component of any OS, especially in multitasking and multi-user environment. The likelihood that there is sufficient memory to load all the data and software for all users simultaneously is extremely small. In practice, a technique of virtual memory is used whereby the available amount of main memory is extended by using secondary storage devices, usually the hard disk. During a typical program execution, not all program instructions and data are required at once. The OS will swap out all unused software and data segments onto disk, until they are actually required.
Secondary storage management
All applications require disk storage – if only to store the application software itself. The OS provides the common access routines to the secondary disk storage devices. It will keep track of data and program file names, physical locations and perform common functions such as the copying, erasing or backing up of data. It also makes the differences in physical hardware as transparent as possible: a data file will appear the same to an application whether the data is being loaded from a diskette, a hard disk or an optical CD-ROM.
Peripheral handler
Apart from managing the memory and secondary storage devices, the OS is usually also responsible for the handling of other peripheral devices. Again, a major objective is to relieve the application from the responsibility of having to cater for a multitude of different possible input and output devices. Thanks to the OS, a program (developer) does not need to cater for the differences between a trackball, mouse or other pointing device. The OS will also ensure that your document will be printed correctly, regardless of whether you have a colour inkjet, a laser or lowly dot-matrix printer attached. Equally, individual programs no longer have to worry about the resolution or capability of your computer monitor. The critical element is again that the applications do not have to worry about the actual hardware connected to the computer system. This is usually achieved by means of device drivers, small software routines that become part of the operating system and help it to interface correctly with specific hardware devices. The device drivers for popular or standard devices are usually already included in the operating system. More esoteric or very new hardware devices will come with a separate disk containing the proper device drivers. These then have to be installed as part of the operating system at the same time as connecting the hardware.
Communications Management
Communications software allows a computer to recognise the presence of other machines on a network, and to grant or restrict access to local files. It also manages network traffic, by monitoring communications lines and diagnosing problems, as well as sending and receiving data to and from remote devices. While PC operating systems include some basic networking and communications facilities, network operating systems (NOS) such as Novell and Unix provide sophisticated management tools for large networks.
User interface
Until the late 1980s, operating systems focussed on the efficient management of resources, tasks and secondary storage. The popularity of personal computers meant that a whole class of less-technical end-users entered the world of computing. This pressured the IT industry into developing a user-friendlier graphical user-interface and the user interface is quickly becoming a significant part of microcomputer operating systems. Different types of user interface have already been discussed earlier in this chapter.
System Utilities
As a logical extension of the operating system, additional system utilities are often required to assist with the proper and optimal use of the computer. Some system utilities may be provided along with the operating system, while others are marketed by independent third-party vendors. A number of system utilities focuses on improving the functionality of the operating system (e.g. better hard disk management) while others provide additional functions (e.g. anti-virus or encryption software). More examples of system utilities are editors, additional security utilities, performance monitors, file viewers, data compression software etc.
- Discovering Information Systems Section 5.4. Authored by : Jean-Paul Van Belle, Mike Eccles, and Jane Nash. Located at : https://archive.org/details/ost-computer-science-discoveringinformationsystems . License : CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
- Abandoned MS DOS 5.0 operating system manual. Authored by : Alexander Synaptic. Located at : https://www.flickr.com/photos/synapticism/15836248264 . License : CC BY-NC: Attribution-NonCommercial