Orange Unit: A Person-Centered Launch
3B: Computer Building Blocks
Background Knowledge Probe
In chapter one, “Introduction to Electronic Circuits,” the background knowledge probe had you create a list of the electronics you make use of on a regular basis. As you did so, you considered who designed it, what parts might have been used inside and out to build and use it, and what you did with any items that started to work less than optimally.
- Now create a new list, this time documenting your daily-use computing devices such as laptops, tablet devices, and smartphones.
- What external and internal electronic components, such as resistors, capacitors, diodes, transistors, switches, sensors, LEDs, copper wires, pins and clips, integrated circuits, and printed circuit boards, come to mind as you think about your computing devices?
- What design choices and design objectives might have inspired the layout of the system and the various circuitry, mechanics, and artistry of its layout function, look, and feel?
- What have you done with any components that started to work less than optimally?
Technical Introduction
- Explore the hardware building blocks that make up all computers.
- Examine the operating system building blocks that provide the major software package that supports the basic functions of a computer and other computing devices.
Computer Hardware Building Blocks
Electronic components like resistors, switches, LEDs, variable resistors, capacitors, other diodes, photocells, transistors, and integrated circuits combine to create many of the everyday devices around us. These can be prototyped using , ultimately leading to the creation of printed circuit boards. All computers are initially made using these prototyping tools as they evolve from innovation and design, to testing, to production and marketing, and distribution.
Inside the case of every computer, we will find one or more printed circuit boards. The is the main board connecting computer parts. It brings together the many different electronic components we have studied, as well as the connectors, sockets, and ports that provide internal and external connections to other electronics.
All computers are made up of the same basic building blocks. In addition to the motherboard, there are several key parts of a computer’s hardware:
- The the core integrated circuit controlling and executing operations.
- , the integrated circuits that temporarily hold data until needed by the CPU or other processors.
- , which includes devices like hard drives, optical media such as DVDs, solid state drives, and flash drives even when power is turned off, but that cannot share data fast enough to work directly with processors.
- , the crossing guards that control the flow of data from inputs to processors, and from processors to outputs.
- that you connect to the computer using Universal Serial Bus, or port, port, jack, audio jack, and others, such as the Raspberry Pi port.
Integrated Circuits
Processors: Do the thinking work
- CPU: The main thinker and boss for the computer
Memory: Hold data until needed by processors; faster than storage but more expensive
- RAM: The main system memory; it forgets when power is off
- Flash: Changes circuits in a way that remembers even without power (USB stick, solid state drive)
Controllers: Move data from inputs to processors and from processors to outputs
Storage
Mechanical changes to media to store data even when power is turned off
- Magnetic media: Uses positive and negative charges (e.g., hard drive)
- Optical media: Uses lasers to detect presence or absence of reflected light (e.g., CD and DVD)
Printed Circuit Boards
System or Motherboard: Main highway connecting components; edge connectors and sockets provide for expansion
- Memory module: Board with group of memory integrated circuits (e.g., DIMM)
- Expansion cards: Board with controller and integrated circuits to add capability to computer (e.g., video card, network card)
Case
- Protects the building blocks from damage
- Holds the power supply used to turn wall power into the power used by components (desktop)
- Provides space for air to flow around and to cool components
- Provides a surface to disperse heat away from components (laptop)
Input/Output Devices
- Input devices let users control the computer (e.g., keyboard and mouse, touch-sensitive devices)
- Output devices inform user what is happening (e.g., monitor, printer)
Computer Operating System Building Blocks
Operating systems are the software managing the various components of a computer’s basic functions, from coordination between the many applications that allow us to do our daily computer-based activities, to the used to span the boundary between programming code and the physical electronics. The building blocks of an operating system can be seen below:
Themes and Skins
- Pre-set package containing graphical appearance details. Supported in some versions of Windows and Linux. Available as third-party applications in other cases.
- Supported for many applications like web browsers.
- Changes the look and feel of many features at once (e.g., background colors, text font and size, icons, mouse cursor, etc.).
Desktop Environment
- The desktop environment is a collection of software that provides a predictable look and feel.
- Includes a Window Manager that controls the placement and appearance of windows, support icons, menus, etc.
- For some operating systems, such as Windows and macOS, the desktop environment is the branded look of the operating system and cannot be changed.
Window System
- This is the part of the graphical user interface that communicates with the kernel.
- Many operating systems allow remote interfacing with the window system, either directly or through third-party applications.
Bundled Software
- Applications like , user managers, software managers.
- Applications like web browsers, text editors, photo and movie editors.
- Device and print drivers determine which hardware is “plug and play” ready.
Kernel
- As the heart of the operating system, it is the go-between from applications to input/output controllers, memory, the CPU, and storage devices.
When working with a computer, names bring things together, hiding from view many of the hardware and operating system building blocks. I’m working right now on a MacBook Air. This laptop has all of the key hardware building blocks pulled together into a single system board within a laptop case. It is installed with the macOS operating system.  This also has all the key hardware building blocks pulled together into a single system board, this time within a smartphone case. It is installed with the Android mobile operating system based on a modified version of the Linux operating system kernel and other open source software. My spouse uses a Lenovo laptop much like the MacBook Air but with a few more I/O ports and a larger laptop screen. It is installed with the Microsoft operating system.
We typically merge the hardware and software together as one device with a means for bringing in human input, using software to collect and respond to that input, and to provide output back to the human.
All modern operating systems include both a graphical user interface (GUI) and a text-based shell known as a command-line interface (CLI) or terminal window. For the most part, we spend our computer time using a keyboard, monitor, and mouse/touchpad to work within these GUIs without even knowing we’re in an operating system that controls each and every action we take on that computer. It’s just the computer and we’re just trying to do our work with a range of applications like web browsers, email clients, and word processors.
Sometimes, though, we need access from a distance, and so we use remote desktop software. In some cases, remote desktop software is operating system independent, as is the case with the Virtual Network Computing (VNC) server installed on the Raspberry Pi Operating System by default, and that can be installed on almost all different personal computers and smartphones. In other cases, it is designed for a specific operating system, as is the case for Apple Remote Desktop (Apple) and Remote Desktop Protocol (Microsoft).
For many server computers, including devices like routers and a range of open-source content management systems (CMS), these are designed to serve as a simple, responsive web interface to a computer that otherwise runs headless. Headless means the computer is run without a monitor, keyboard, and/or mouse connected to it. The content management system provides us with a remote interface device to access and use certain tasks that would otherwise be accessed using a GUI through a keyboard, mouse, and monitor or through a remote desktop application.
Another common way to work with headless devices is through a Universal Asynchronous Receive and Transmit (UART) serial connection or an Internet-based secure shell (SSH) connection. These serve to provide a simple, text-based shell, also sometimes called a console or terminal window. Indeed, the Raspberry Pi starter kit provides a default backup to connect a personal computer to a server or microcomputer using a USB (Universal Serial Bus) to TTL (Transistor Transistor Logic) cable to facilitate UART communications as a way to assure troubleshooting when all other means for user interface with a device has failed. This is how we’ll start our work with the Raspberry Pi.
Where Does the OS Live?
The operating system is installed and maintained using a storage device like a hard drive or MicroSD card. But storage devices are like our old paperwork that we store up in an attic. We can’t do anything with it beyond just storing it there. When a computer is turned on, those instruction sets in the operating system which are immediately needed are moved out of storage and into random access memory (RAM). We sometimes call this booting a computer, also called boot up or start up. This startup sequence first does a safety check of the system, then looks to one or more possible locations for the master boot record or boot manager, which then takes over control to bring forward the next modules of operating system code needed.
The reason we need to boot up is because RAM can only store information as long as it has power and ground to complete the circuits used to input, store, and output the memory. This is compared to the older long term storage devices like hard drives, and to newer storage devices like secure digital (SD) cards and other flash memory, all of which have means for permanently writing memory to spaces on them while also allowing reading, deleting, and rewriting to those spaces as needed, albeit more slowly. RAM is like paper files within an arm’s reach of a computer we’re working on at the moment.
But as is the case with many of the papers we may have sitting in close reach of the computer on our desk, they still can’t be actually read and processed. To do this, a computer next moves sequences of code from dynamic RAM (DRAM), which can store larger amounts of data at a more affordable rate but that still works a bit too slowly for static RAM (SRAM), which doesn’t need to be refreshed and that is faster than DRAM. SRAM serves as a system cache that works closely with the Central Processing Unit, or CPU.
At any given moment, where a segment of the operating system is “living” depends on what modules, functions, variables, iterations, and sequences of code are needed. It is moving from attic to desk to hand to brain to hand to brain to desk to hand to brain to desk to attic over and over billions of times per second.
The Kernel: The Heart of the Operating System
The operating system is the underlying program that we generally don’t even know really exists. We hear about it, for instance when we buy a computer running Microsoft Windows 10, or an Apple MacBook running macOS Sierra. And once in a great while we’re encouraged or required to install a new version of the operating system.
But generally we just see lots of text and graphics on a monitor, and we type on our keyboard, move around a pointer from one place to another using a mouse or touchpad or even sometimes the monitor itself. That’s the user interface side. But the heart of the operating system lives in the kernel.
- The kernel controls how applications get time on the CPU(s) of the computer. There was a day when the OS only allowed one application at a time to physically run on the computer. Imagine having to save your work in your text editor, exit, then open the spreadsheet to see your data, then exit, then reopen your text editor. Today operating systems are multi-tasking, allowing multiple applications to all “run” simultaneously. They do this using a very fast time sharing strategy, in which each application is allowed to submit threads, or small segments of programming code, to the operating system, requesting execution of that thread.
- The kernel controls memory access at several levels:
- Physical memory vs. virtual memory: Applications can easily eat up all available memory. To that extent, the OS must carefully control just how much memory is being used by a specific application. Further, when a user wants to do more than can be done with available memory, the operating system controls the movement of bits from physical memory to virtual memory or swap space, a special location on the hard drive configured to mimic, albeit very slowly, physical memory. Applications cannot directly access virtual memory, so when memory runs short, the OS spends a lot of time swapping bits between physical and virtual memory.
- Shared vs. private address space: Some operating systems conserve physical memory allocation by only loading shared segments of code (for instance from a library file) once, then pointing all applications to this shared address space. The problem is that sometimes a badly behaving application can overwrite a critical shared code with corrupted data. In the worst cases, this can lead to a general protection fault (a type of system error). Many modern operating systems therefore decide to make greater use of private address space, always loading segments of code again even if they already exist in memory.
- The kernel controls interactions with device controllers. Because there are many controllers manufactured for each type of input/output function (for instance, video controllers), an operating system cannot be expected to know how to interface with every one of them out of the box. Instead, each controller must come with its own device driver that can translate between the specific controller and the specific operating system. All hardware incompatibilities boil down to unavailable device drivers for the specific operating system.
- The kernel of the operating system determines which types of file systems are supported.
In all cases, it is the kernel of the operating system that does the core work of communication between electronics and programming code.
A Brief History of Operating Systems
In Microsoft and Apple operating systems, they’ve put together a tightly intertwined, large set of applications to cover all main aspects of the operating system, from user interface, to bundled applications to configure the computer, store, delete, and access files, to install and update applications, to set up screensavers, accounts, and passwords, to disk and monitor management, and so much more. And the operating system has the essential instruction sets needed to interact with the electronics of the computer within the kernel, the most basic level of the operating system.
Before there was Microsoft or Apple, there was Unix, a family of multitasking, multiuser computer operating systems. Unix was first developed by AT&T at Bell Labs research center in the 1970s, but then was split into a few different Unix systems. All are commercial, at least at some level, although some have been made more widely available than others. For the most part, Unix provides a distinction between the kernel of the operating system, primary bundled applications, the user interface, and any networked information systems used to pass data back and forth with devices beyond the kernel.
Very early in its development, Unix developers created the X-Window system to provide the ability to create graphical user interfaces. The developers also set up Unix to work on the Internet. In this way, even back in the ’70s and ’80s, Unix was able to have a graphical user interface to a headless computer using simple (actually called ‘dumb’ at the time) computers that served primarily as a text and sometimes graphical human interface device to the Unix core computer.
One company that entered into a licensing contract to use and build their own iteration of Unix was Apple, leading to the macOS.
Microsoft wrote their own text-based operating system, called MS-DOS, or Microsoft Disk Operating System. It was meant to support a personal (that is, only one user working only with directly attached devices) computer, and included the kernel, basic bundled applications, and a text interface. They then later added their own Windows graphical user interface extension to MS-DOS. Later still, they created a new version of the operating system called Windows NT (New Technology) that integrated the kernel, bundled applications, and graphical user interface into one, while still also staying compatible with earlier versions of Windows. Ultimately, they made the break to create newer versions of the Windows operating system, and eventually also adding back a new and improved text-based terminal window. But throughout, their choices on select keyboard options, labels, and other essential communications have contrasted with those of Unix, and thereby with those of Apple as well.
Moving into the early 1990s, Unix computers were relatively expensive, and therefore were purchased by, and used in, research labs. Then in 1991 University of Helsinki student Linus Torvalds purchased an Intel 80386-based clone of the IBM PC mini-Unix called MINIX. Later that year, he made public his first prototype of a Unix-like kernel operating system he called Linux. On March 14, 1994, he released version 1.0. From the start, he released Linux using Richard Stallman’s General Public License. Stallman, a free software advocate, created the GNU Project, a software development initiative. By combining the GNU Project essential bundled applications with the Linux core, Torvalds built and released a fully functioning operating system.
Over the years, different groups have worked to create distributions of specific GNU applications, other applications, and a Linux core. The oldest surviving distribution of Linux is called Slackware, created by Patrick Volkerding in 1992. Slackware 1.0 came on 24 floppy disks and was built on top of Linux kernel version 0.99. I started working in the Neuronal Pattern Analysis Group of the Beckman Institute at the University of Illinois Urbana-Champaign in 1993 and soon after began using Slackware and Linux along with the newly developing X-Mosaic graphical web browser as part of a team seeking to use the Internet to make publicly available raw electrophysiology data which was collected as part of various research projects.
Two common distributions of Linux are used as the starting point for a rich variety of child distributions. One is called Fedora, and originated in 1995, under the name Red Hat Linux. In 2003, the Red Hat trademark was used to create two branches: Red Hat Enterprise, with a combination of free and open source applications and commercial applications, and Fedora, a community-oriented distribution designed for “hobbyists.” Commonly used distributions with Fedora at their core include CentOS and Scientific Linux.
Debian GNU/Linux was first announced in 1993 by its founder, Ian Murdock. It has been developed to every extent possible as a completely non-commercial project, through collaboration with over 1000 volunteer developers. Widely used Debian-based alternatives include the overall most widely used distribution, Ubuntu, and Raspberry Pi OS, the default Debian-based alternative for the Raspberry Pi microcomputer.
There are two widely used commercial operating systems based on the Linux kernel today as well. In September 2008, Google launched its Android operating system using a modified version of the Linux kernel and various open source software designed for touchscreen mobile devices, and subsequently developed for Android TV, Android Auto, and Wear OS. The Android Open Source Project is used for development of its core source code, and apps for Android can therefore be developed by anyone for virtually any purpose and installed and run on Android devices. In May 2011, Google released the first Chromebook, running the Chrome OS. It is only available preinstalled on hardware from Google manufacturing partners. Its open source equivalent, Chromium OS, can be freely installed.
Specific to Raspberry Pi OS, each major new release of Debian results in a major new release of Raspberry Pi OS. The code name used for each major release of Debian is taken from Toy Story characters. In 2013, this was Wheezy, the penguin character by that name. In 2015, this was Jessie, the cowgirl character. As of June 2017, this is Stretch, the rubber octopus from Toy Story 3. As noted in these code name release dates, Debian works to be stable through a conservative update process. The stable release is held for about two years, although test releases become available via the new code name during the interim for those wanting early access for use and testing of new designs.
Exercise: Reviewing Your Computer
Take some time to dig into the hardware, operating system, and major installed software applications of your primary computer. While it’s often more difficult, if even possible, to open up your computer to look at the system or motherboard of the computer than it used to be, if you can safely do that, do so. You may have received some default documentation with your computer, either in print or digital. There may be “About this Computer” links available on the computer or on a vendor’s website. Some resources are best accessed through applications that came with your computer and that provide current notes which can account for potential updates that have since replaced the defaults that came with the computer.
Using these resources, create your own list of the physical components and operating system of your computer:
- Input/output devices, such as types of USB ports, Thunderbolt ports, audio, camera, Ethernet, Bluetooth, card readers, etc.
- Type and amount of random access memory (RAM)
- Storage devices
- Central processing unit (CPU) and, if included, graphic processing unit (GPU)
- Power source
- Operating system (OS) type and version.subversion/edition
- Windowing system, desktop environment, and themes/skins. For many computers today, these are highly integrated, so you may only see this as a singular graphical user interface system.
Take time to compare and contrast this with some of the other desktop and laptop computers that you or others around you use on a fairly regular basis.
 The core components of these devices have remained the same, even as the specifications, standards, and physical and software implementations have been shaped and reshaped repeatedly over the last 50+ years. Knowing at least a bit about the items within all devices is essential as we serve professional and personal roles in the selection, implementation, innovation-in-use, and support of these devices in our varying contexts.
Before we move on to examining the Raspberry Pi microcomputer, take a few moments to watch this “teardown” video from electronics repair company iFixit. A product teardown is a common method for identifying the component parts of an electronic device, in order to better refurbish or repair devices of that same model. However, take caution and browse the resources available from iFixit before tearing down your own device, as the manufacturer may claim that such actions void your warranty. Moreover, for many newer devices, components are glued — not screwed — together, requiring specialized equipment to get inside the device.
In this teardown video, a 2018 MacBook Air is disassembled and evaluated. As you watch, make note of any parts you recognize. For even more detail, read the full teardown guide.
Comprehension Check
A breadboard used to be a board (sometimes literally a board for cutting bread) with nails pounded into it so that you could wrap wires around them to make experimental models of electric circuits. Today, the breadboard is a piece of plastic with holes in it. Underneath each hole is a metal clip. These metal clips connect together a specified set of holes ordered into a row or column. This way, pushing a piece of conductive material into one hole right away connects that material to things pushed into other holes that are joined together by that clip.
A perfboard is a thin, rigid sheet with holes but no metal clips on the other side. Instead, copper pads are used, to which conductors can be soldered. In some cases, as with the perma-proto breadboards from Adafruit, copper is further used to group together certain holes, mimicking the breadboard in a way that provides greater durability for prototyping work.
The printed circuit board found in a computer, which contains the principal components, along with ports and connectors to other devices. The term "motherboard" arose at a time when it was paired with one or more supporting printed circuit expansion boards, often referred to as daughterboards or expansion cards, in order to achieve the full general functioning of the computer. The motherboard is sometimes also referred to as system board or mainboard.
The CPU is the central processor of a computer. It is built of an ever-growing number of electronic circuits enabling it to carry out the basic arithmetic, logic, controlling, and input/output operation instructions for the computer. Over the decades, more electronic components have been placed on a single and increasingly small integrated circuit (IC) chip. Today's CPUs are actually multi-core processors, with one chip being constructed of two or more CPUs called "cores." It is on the CPU that instructions for the vast majority of programming code is actually run. The CPU uses three main steps: fetch, decode, and execute, after which the instruction is returned to a memory integrated circuit.
Memory is the part of a computer in which data or programming instructions are stored and retrieved. Memory is constructed using high-performance integrated circuit chips to increase performance as compared to storage devices such as hard drives and lower performance but less expensive flash drive integrated circuit chips. Much of this type of memory is volatile Random Access Memory (RAM), in which data is lost when power to the computer is turned off. There are multiple types of RAM: The higher cost but faster performing static RAM (SRAM) is used with the CPU to increase CPU performance, while the less costly but slightly slower dynamic RAM (DRAM), or more recently double data rate synchronous dynamic RAM (DDR SDRAM) is the main memory of computers. The Raspberry Pi Model 3 comes with 1 GB (Gigabyte) of DDR, while the Raspberry Pi Model 4 is available with 1GB, 2GB, or 4GB of DDR, making it very similar to today's smartphone and Chromebook computers. Many laptops today come with 4GB to 8GB of system memory.
There are a range of different data storage devices: hard drives (HDDs) constructed using magnetic charges placed on a set of spinning platters, DVDs using pits on a spinning platter read via laser, and flash memory integrated circuit chips, such as Solid State Drives (SSDs), USB flash drives, and SD cards, provide computers with long term storage of data and software applications. Storage devices are relatively slow, so programming instructions need to be moved from storage to memory using integrated circuits to be fetched, decoded, and executed by the processors of the computer. The Raspberry Pi kit includes an 8 GB MicroSD card storage device, although 16GB, 32GB, and 128GB MicroSD cards are available and can be used with the Raspberry Pi. In addition, it is sometimes helpful to make use of USB flash drives or USB hard drives with the Raspberry Pi to provide even more storage.
An integrated circuit that interfaces with one or more other devices on a printed circuit board. Besides the CPU, this can include input/output controller(s) and a graphic processing unit (GPU) controller. The Raspberry Pi Model 3 has two controllers, the System-on-Chip (SoC) controller that includes the CPU and computer memory, and a controller interfacing with the wired Ethernet and four USB ports.
Input devices let users control the computer (e.g. keyboard, mouse, touch-sensitive devices). Output devices inform the user of what is happening (e.g. monitor, printer).
Universal Serial Bus (USB) is a formal industry standard with specifications for cables and connectors, and also protocols for connections, communication, and power supply between electronic devices such as computers and peripherals. USB 1.x, 2.0, 3.x, and the upcoming 4 are generations of the standard and associated specifications. The USB port connector on a device is called the receptacle, while the connector on the cable is called the plug. There is a range of different USB connectors approved within USB committee specifications, including:
Standard format USB Type-A (common on computers, and used on the Raspberry Pi) and Type-B connectors (seen in a range of removable devices such as external hard drives and printers). Type-A receptacles on devices are color-coded white, indicating USB version 1 or 2 compliant low/full/high speed ports, or blue, indicating USB version 3.x SuperSpeed compliant ports.
Mini-A (common in cameras and some tablet computers) and Mini-B connectors.
Micro-A and Micro-B connectors, common in many mobile devices. For USB 3.x ports, a thin but wider Micro-B SuperSpeed plug is used.
USB-C is a formal connector specification, and does not necessarily implement USB 3.x standards.
Computers incorporate a range of audio/video interfaces, depending on vendor. Some of the most common interfaces currently in use include:
High-Definition Multimedia Interface (HDMI), a proprietary audio/video interface standard, currently at version 2.X. This is included as the display port on the Raspberry Pi Model 3 and Model 4 microcomputers.
DisplayPort (DP) is a VESA standard digital display interface, and is backward compatible with other interfaces such as HDMI. Apple computers use the Apple-designed Mini DisplayPort (mDP), although beginning in 2016 Apple began moving towards use of the USB-C connector.
Thunderbolt is the brand name of an interface standard developed by Intel and Apple. The standard allows the multiplex of individual data lanes from multiple connected devices to a single DisplayPort (DP) or Mini DisplayPort (mDP) (Thunderbolt versions 1 and 2) or USB-C (Thunderbolt version 3) connector.
An Ethernet port is an Institute of Electrical and Electronics Engineers (IEEE) standard connector for 100BASE-Tx/1000BASE-T full duplex Fast and Gigabit wired Ethernet communications using twisted pair CAT-5 and CAT-6 copper cabling.
A general purpose input/output, or GPIO, is a common, open-ended transmission mechanism used with integrated circuits on microcontrollers, microcomputers, and other printed circuit board electronics. Pins are provided to which female-ended wires can be connected. GPIO pins can be programmed as input (e.g., sensor data; ground) or output (e.g., state change; power) sources. GPIO pins can be preconfigured for special purposes, or can remain undefined until specified by a user at run time. In general, GPIO provides a means to tailor pins to fit specific design goals within applications, as well as reusability across applications.
The heart of the operating system. It is the go-between from applications between input/output controllers, memory, the Central Processing Unit (CPU) and storage devices.
A file manager is a software program that helps you manage all the files on your computer. For example, file managers allow you to view, edit, copy, and delete the files on your computer's storage devices. It is known as the File Manager within the Windows Operating System and as the Finder on the Mac Operating System. The file manager makes use of the Graphical User Interface (GUI). The same tasks you can complete with the file manager can also be done through the Command Line Interface (CLI) terminal.


9.7 Mammals
Mary Ann Clark; Jung Choi; and Matthew Douglas
Learning Objectives
By the end of this section, you will be able to do the following:
- Name and describe the distinguishing features of the three main groups of mammals
- Describe the likely line of evolutionary descent that produced mammals
- List some derived features that may have arisen in response to mammals’ need for constant, high-level metabolism
- Identify the major clades of eutherian mammals
Mammals, comprising about 5,200 species, are vertebrates that possess hair and mammary glands. Several other characteristics are distinctive to mammals, including certain features of the jaw, skeleton, integument, and internal anatomy. Modern mammals belong to three clades: monotremes, marsupials, and eutherians (or placental mammals).
Characteristics of Mammals
The presence of hair, composed of the protein keratin, is one of the most obvious characteristics of mammals. Although it is not very extensive or obvious on some species (such as whales), hair has many important functions for most mammals. Mammals are endothermic, and hair traps a boundary layer of air close to the body, retaining heat generated by metabolic activity. Along with insulation, hair can serve as a sensory mechanism via specialized hairs called vibrissae, better known as whiskers. Vibrissae attach to nerves that transmit information about tactile vibration produced by sound sensation, which is particularly useful to nocturnal or burrowing mammals. Hair can also provide protective coloration or be part of social signaling, such as when an animal’s hair stands “on end” to warn enemies, or possibly to make the mammal “look bigger” to predators.
Unlike the skin of birds, the integument (skin) of mammals includes a number of different types of secretory glands. Sebaceous glands produce a lipid mixture called sebum that is secreted onto the hair and skin, providing water resistance and lubrication for hair. Sebaceous glands are located over most of the body. Eccrine glands produce sweat, or perspiration, which is mainly composed of water, but also contains metabolic waste products, and sometimes compounds with antibiotic activity. In most mammals, eccrine glands are limited to certain areas of the body, and some mammals do not possess them at all. However, in primates, especially humans, sweat glands are located over most of the body surface and figure prominently in regulating the body temperature through evaporative cooling. Apocrine glands, or scent glands, secrete substances that are used for chemical communication, such as in skunks. Mammary glands produce milk that is used to feed newborns. In both monotremes and eutherians, both males and females possess mammary glands, while in marsupials, mammary glands have been found only in some opossums. Mammary glands likely are modified sebaceous or eccrine glands, but their evolutionary origin is not entirely clear.
The skeletal system of mammals possesses many unique features. The lower jaw of mammals consists of only one bone, the dentary, and the jaw hinge connects the dentary to the squamosal (flat) part of the temporal bone in the skull. The jaws of other vertebrates are composed of several bones, including the quadrate bone at the back of the skull and the articular bone at the back of the jaw, with the jaw connected between the quadrate and articular bones. In the ear of other vertebrates, vibrations are transmitted to the inner ear by a single bone, the stapes. In mammals, the quadrate and articular bones have moved into the middle ear. The malleus is derived from the articular bone, whereas the incus originated from the quadrate bone. This arrangement of jaw and ear bones aids in distinguishing fossil mammals from fossils of other synapsids (see figure below).
The adductor muscles that close the jaw comprise two major muscles in mammals: the temporalis and the masseter. Working together, these muscles permit up-and-down and side-to-side movements of the jaw, making chewing possible—which is unique to mammals. Most mammals have heterodont teeth, meaning that they have different types and shapes of teeth (incisors, canines, premolars, and molars) rather than just one type and shape of tooth. Most mammals are also diphyodonts, meaning that they have two sets of teeth in their lifetime: deciduous or “baby” teeth, and permanent teeth. Most other vertebrates with teeth are polyphyodonts, that is, their teeth are replaced throughout their entire life.
Mammals, like birds, possess a four-chambered heart; however, the hearts of birds and mammals are an example of convergent evolution, since mammals clearly arose independently from different groups of tetrapod ancestors. Mammals also have a specialized group of cardiac cells (fibers) located in the walls of their right atrium called the sinoatrial node, or pacemaker, which determines the rate at which the heart beats. Mammalian erythrocytes (red blood cells) do not have nuclei, whereas the erythrocytes of other vertebrates are nucleated.
The kidneys of mammals have a portion of the nephron called the loop of Henle or nephritic loop, which allows mammals to produce urine with a high concentration of solutes—higher than that of the blood. Mammals lack a renal portal system, which is a system of veins that moves blood from the hind or lower limbs and region of the tail to the kidneys. Renal portal systems are present in all other vertebrates except jawless fishes. A urinary bladder is present in all mammals.
Unlike birds, the skulls of mammals have two occipital condyles, bones at the base of the skull that articulate with the first vertebra, as well as a secondary palate at the rear of the pharynx that helps to separate the pathway of swallowing from that of breathing. Turbinate bones (chonchae in humans) are located along the sides of the nasal cavity, and help warm and moisten air as it is inhaled. The pelvic bones are fused in mammals, and there are typically seven cervical vertebrae (except for some edentates and manatees). Mammals have movable eyelids and fleshy external ears (pinnae), quite unlike the naked external auditory openings of birds. Mammals also have a muscular diaphragm that is lacking in birds.
Mammalian brains also have certain characteristics that differ from the brains of other vertebrates. In some, but not all mammals, the cerebral cortex, the outermost part of the cerebrum, is highly convoluted and folded, allowing for a greater surface area than is possible with a smooth cortex. The optic lobes, located in the midbrain, are divided into two parts in mammals, while other vertebrates possess a single, undivided lobe. Eutherian mammals also possess a specialized structure, the corpus callosum, which links the two cerebral hemispheres together. The corpus callosum functions to integrate motor, sensory, and cognitive functions between the left and right cerebral cortexes.
Evolution of Mammals
Mammals are synapsids, meaning they have a single, ancestrally fused, postorbital opening in the skull. They are the only living synapsids, as earlier forms became extinct by the Jurassic period. The early non-mammalian synapsids can be divided into two groups, the pelycosaurs and the therapsids. Within the therapsids, a group called the cynodonts are thought to have been the ancestors of mammals (see figure below).
As with birds, a key characteristic of synapsids is endothermy, rather than the ectothermy seen in many other vertebrates (such as fish, amphibians, and most reptiles). The increased metabolic rate required to internally modify body temperature likely went hand-in-hand with changes to certain skeletal structures that improved food processing and ambulation. The later synapsids, which had more evolved characteristics unique to mammals, possess cheeks for holding food and heterodont teeth, which are specialized for chewing, mechanically breaking down food to speed digestion, and releasing the energy needed to produce heat. Chewing also requires the ability to breathe at the same time, which is facilitated by the presence of a secondary palate (comprising the bony palate and the posterior continuation of the soft palate). The secondary palate separates the area of the mouth where chewing occurs from the area above where respiration occurs, allowing breathing to proceed uninterrupted while the animal is chewing. A secondary palate is not found in pelycosaurs but is present in cynodonts and mammals. The jawbone also shows changes from early synapsids to later ones. The zygomatic arch, or cheekbone, is present in mammals and advanced therapsids such as cynodonts, but is not present in pelycosaurs. The presence of the zygomatic arch suggests the presence of masseter muscles, which close the jaw and function in chewing.
In the appendicular skeleton, the shoulder girdle of therian mammals is modified from that of other vertebrates in that it does not possess a procoracoid bone or an interclavicle, and the scapula is the dominant bone.
Mammals evolved from therapsids in the late Triassic period, as the earliest known mammal fossils are from the early Jurassic period, some 205 million years ago. One group of transitional mammals was the morganucodonts, small nocturnal insectivores. The jaws of morganucodonts were “transitional,” with features of both reptilian and mammalian jaws. Like modern mammals, the morganucodonts had differentiated teeth and were diphyodonts (see figure below). Mammals first began to diversify in the Mesozoic era, from the Jurassic to the Cretaceous periods. Even some small gliding mammals appear in the fossil record during this time period. However, most of the Jurassic mammals were extinct by the end of the Mesozoic. During the Cretaceous period, another radiation of mammals began and continued through the Cenozoic era, about 65 million years ago.
Living Mammals
There are three major groups of living mammals: monotremes (prototheria), marsupials (metatheria), and placental (eutheria) mammals. The eutherians and the marsupials together comprise a clade of therian mammals, with the monotremes forming a sister clade to both metatherians and eutherians.
There are very few living species of monotremes: the platypus and four species of echidnas, or spiny anteaters (see figure below). The leathery-beaked platypus belongs to the family Ornithorhynchidae (“bird beak”), whereas echidnas belong to the family Tachyglossidae (“sticky tongue”). The platypus and one species of echidna are found in Australia, and the other species of echidna are found in New Guinea. Monotremes are unique among mammals because they lay eggs, rather than giving birth to live young. The shells of their eggs are not like the hard shells of birds, but they have a leathery shell, similar to the shells of reptile eggs. Monotremes retain their eggs through about two-thirds of the developmental period, and then lay them in nests. A yolk-sac placenta helps support development. The babies hatch in a fetal state and complete their development in the nest, nourished by milk secreted by mammary glands opening directly to the skin. Monotremes, except for young platypuses, do not have teeth. Body temperature in the three monotreme species is maintained at about 30°C, considerably lower than the average body temperature of marsupial and placental mammals, which are typically between 35 and 38°C.
Over 2/3 of the approximately 330 living species of marsupials are found in Australia, with the rest, nearly all various types of opossum, found in the Americas, especially South America. Australian marsupials include the kangaroo, koala, bandicoot, Tasmanian devil, and several other species (see figure below). Like monotremes, the embryos of marsupials are nourished during a short gestational period (about a month in kangaroos) by a yolk-sac placenta, but with no intervening egg shell. Some marsupial embryos can enter an embryonic diapause, and delay implantation, suspending development until implantation is completed. Marsupial young are also effectively fetal at birth. Most, but not all, species of marsupials possess a pouch in which the very premature young reside, receiving milk and continuing their development. In kangaroos, the young joeys continue to nurse for about a year and a half.
Eutherians (placentals) are the most widespread and numerous of the mammals, occurring throughout the world. Eutherian mammals are sometimes called “placental mammals” because all species possess a complex chorioallantoic placenta that connects a fetus to the mother, allowing for gas, fluid, and nutrient exchange. There are about 4,000 species of placental mammals in 18 to 20 orders with various adaptations for burrowing, flying, swimming, hunting, running, and climbing. In the evolutionary sense, they have been incredibly successful in form, diversity, and abundance. The eutherian mammals are classified into two major clades, the Atlantogenata and the Boreoeutheria. The Atlantogenata include the Afrotheria (e.g., elephants, hyraxes, and manatees) and the Xenarthra (anteaters, armadillos, and sloths). The Boreoeutheria contain two large groups, the Euarchontoglires and the Laurasiatheria. Familiar orders in the Euarchontoglires are the Scandentia (tree shrews), Rodentia (rats, mice, squirrels, porcupines), Lagomorpha (rabbits and hares), and the Primates (including humans). Major Laurasiatherian orders include the Perissodactyla (e.g., horses and rhinos), the Cetartiodactyla (e.g., cows, giraffes, pigs, hippos, and whales), the Carnivora (e.g., cats, dogs, and bears), and the Chiroptera (bats and flying foxes). The two largest orders are the rodents (2,000 species) and bats (about 1,000 species), which together constitute approximately 60 percent of all eutherian species.
Section Summary
Mammals are vertebrates that possess hair and mammary glands. The mammalian integument includes various secretory glands, including sebaceous glands, eccrine glands, apocrine glands, and mammary glands.
Mammals are synapsids, meaning that they have a single opening in the skull behind the eye. Mammals probably evolved from therapsids in the late Triassic period, as the earliest known mammal fossils are from the early Jurassic period. A key characteristic of synapsids is endothermy, and most mammals are homeothermic.
There are three groups of mammals living today: monotremes, marsupials, and eutherians. Monotremes are unique among mammals as they lay eggs, rather than giving birth to young. Marsupials give birth to very immature young, which typically complete their development in a pouch. Eutherian mammals are sometimes called placental mammals, because all species possess a complex placenta that connects a fetus to the mother, allowing for gas, fluid, and nutrient exchange. All mammals nourish their young with milk, which is derived from modified sweat or sebaceous glands.
Review Questions
Critical Thinking Questions
Glossary
- apocrine gland
- scent gland that secretes substances that are used for chemical communication
- dentary
- single bone that comprises the lower jaw of mammals
- diphyodont
- refers to the possession of two sets of teeth in a lifetime
- eccrine gland
- sweat gland
- eutherian mammal
- mammal that possesses a complex placenta, which connects a fetus to the mother; sometimes called placental mammals
- heterodont tooth
- different types of teeth that are modified for different purposes
- mammal
- group of endothermic vertebrates that possesses hair and mammary glands
- mammary gland
- in female mammals, a gland that produces milk for newborns
- marsupial
- group of mammals that includes the kangaroo, koala, bandicoot, Tasmanian devil, and several other species; young develop within a pouch
- monotreme
- egg-laying mammal
- Ornithorhynchidae
- clade that includes the duck-billed platypus
- sebaceous gland
- in mammals, a skin gland that produces a lipid mixture called sebum
- Tachyglossidae
- clade that includes the echidna or spiny anteater


LEARNING TASK 2 : Describe short-term hazards in the trades
Working around vehicles and heavy equipment
Workers are often required to work near vehicles and mobile equipment. It is the workers’ responsibility to keep out of the way. Workers working near moving vehicles and equipment should:
- stay alert at all times and keep a safe distance
- stay out of the circle formed by the extended bucket of an excavator (swing)
- never get into blind spots of operators
- maintain eye contact with the operator
- never stand under loads handled by lifting or digging equipment, or near vehicles being loaded or unloaded
- wear reflective or high-visibility vests, hard hats, steel-toed boots, and appropriate hearing protection while working near equipment
- alert the operator of any impending hazards, electrical wires, gas lines, sewer or water lines, etc.


Learning Objectives
- Learning basic tech needs
- Understanding recording options
- Choosing the right equipment for your budget
For most people, entry-level access to producing a podcast involves recording equipment, a computer, internet connection, and editing software. Choices will be influenced by your pocketbook, experience, and personal preferences but this guide emphasizes free or low-cost equipment.
There are three main styles of podcast microphones: hand-held, stand, and lavalier and they all have pros and cons. That should not be confused with the pickup pattern within a microphone and is explained a bit later.
Recording a podcast can be as simple as using your smartphone or as complex as recording in a professional studio. There are free and low-cost options to consider as well as professional-level resources available to many schools, universities, and businesses.
At the most basic level, a smartphone app can be your microphone for recording. On the iPhone, Voice Memo can be launched from your home screen for interviews and narration, and the same is true for androids.
The audio quality is so good that some professional radio reporters just use their iPhones for newsgathering instead of separate digital audio recorders. Neal Augenstein of WTOP radio in Washington, D.C., pioneered the use of the iPhone for professional radio reporting. Android phones also offer low-cost voice apps.
Be sure to have an external hard drive to download the audio off the phone so it doesn’t take up valuable space on your computer hard drive and slow overall operation.
A smartphone works well for voice-over recording/narration by one person. However, when recording both an interviewer and interviewee and when gathering ambient sound from the environment, some extra help is needed.
Your iPhone or iPad can be turned into a high-quality field recorder like a Zoom H4n, by using an X/Y microphone attachment for under $80 but note that it uses a lightning connection.
While this attachment saves you the cost of buying a field recorder, I’ve found it to be a bit cumbersome because your phone needs to be connected without a protective phone case in order for the lightning connector to be solid.
While it’s possible to use the built-in microphone of a computer to record audio, it’s not the preferred method because the sound is distant and hollow-sounding, which is irritating to listen to for any length of time.
A vast improvement in recording audio quality can be achieved by doing the following:
Handheld microphones can be held or put into a mic stand or attached using a boom arm for very good for recording in the field as well as in a home studio.
Some good choices under $100 include the ATR2100 and Samson QU2 microphones. Both are dynamic mics, which are considered better for live recording and both have USB and XLR connections. USB connects directly to the computer while an XLR three-pin cable connector can be used for higher-end recording using either audio recorders or audio board mixers.
For a deal, look at buying streaming or podcast equipment packages such as this one from Audio-Technica. Prices start at $130 for a mic with USB and XLR connections, headphones and an adjustable boom arm. For a few dollars more, get a windscreen for the mic. There also are packages that include the mic, windscreen, tripod, and earphones.
To find the best equipment for your needs, online reviews can be helpful but note that reviewers can be influenced if they receive a fee from the manufacturer.
Higher Quality Mics
Reviews
In addition to using a handheld mic like the ATR2100 for recording, I use a Yeti microphone because I can assign the pickup pattern to my recording circumstances. After 28 years the well-known ‘Blue’ Yeti brand was retired by Logitech.
I use the cardioid pickup pattern when recording solo and the bidirectional setting when doing an in-person interview – this setting puts the sound in front of the interviewer and the guest, rejecting sound from the sides.
The Yeti is already a standing microphone so there’s no need to buy an additional stand and it has a USB connection that plugs directly into my computer.
However, the Yeti can also be taken out of the stand and put into a boom arm with a shock mount, so the mic can move in a horizontal plane – allowing for better positioning of the mic, reducing noise from vibrations, and creating more desk space. Since the Yeti is heavy be sure to get a strong boom arm, which can cost $100.
Lavalier microphones get direct sound because the mic attaches to a speaker’s clothing and then to the audio recorder or a mobile phone with an input jack. However, because lav mics tend to have an omnidirectional pickup pattern that easily picks up sound from all directions, it’s distracting for a podcast.
Before ordering any equipment be sure to check compatibility with your smartphone. Exercise caution because not all adapters work that well and you may not know that until you test it. Technology will evolve so keep looking for solutions and checking for the latest news via publications listed at the end of this chapter.
Each type of microphone has a pickup pattern inside that determines how sound enters — it’s not something you can see by just looking at a microphone.
Cardioid mics pick up sound mostly from the front of the mic; bi-directional mics from the front and back (making it ideal for interviews); and omnidirectional mics pick up sound from all sides, which is not ideal for podcasts.
Radio and television reporters often also have the luxury of a shotgun microphone – which picks up sound narrowly that is right in front of the mic and rejects sound from the sides and rear.
To improve recordings, microphones can have pop filters that go in front of or surround a microphone. These are also called pop shields, windscreens or dead cats. They block out plosives — the popping and hissing sound often heard on words with the letters p, b, t, d, k, and g.
When it comes to handheld microphones, you’ll need a sturdy mic stand or add a shock mount around the mic to minimize vibrations. However, this isn’t essential and some are included in equipment packages.
Headphones should be used when recording interviews and when editing rather than relying on a computer’s speakers. While earbuds work okay, they are really better for gaming rather than podcasting, so look for headphones that cover the ears.
If your budget allows, invest in “cans” or closed-back headphones that go over your ears for better quality.
Digital audio recorders start with the budget-friendly Zoom H1n and increase in price for later models. Other recorders from Tascam are around the same price point, with more expensive advanced models from Sony and Marantz.
Keep in mind that you will need to buy multimedia cards if you plan to record for a longer period of time than the memory card has which comes with the recorder.
Zoom H1n-$119; prices higher for H4n, H6, H8
Zoom calls the Podtrak P4 the “first recorder designed specifically for podcasters,” at $173.
The Zoom Podtrack P4 has space for four mics, two echo-free remote call-ins and separate headphone feeds for all your guests.
Here’s a video look at the features.
Once you go beyond recording one or two people, getting a good-quality recording gets more complicated and expensive.
While USB mics are popular because they plug directly into the computer – however, in most instances using two USB mics in one computer is neither easy nor recommended. The computer will have trouble recognizing a second USB, especially if they are the same type, like a Yeti.
A typical workaround involves more expense than you likely need at the start. An audio interface or mixer works as a bridge between the microphones and computer to allow multiple mic connections with other inputs, such as XLR connections.
The mic goes into the audio interface, which then plugs into your computer on a USB or thunderbolt cable. The recording is sent to your computer using audio software. Be sure to note how many USB outlets are on a particular model of the mixer as the price goes up with more outlets.
Most beginning podcasters don’t use popular interfaces like the Focusrite Scarlett or Tascam because they can be complicated and cost $180 on up. Other mixer options are reviewed for price and function by Discoverpods.com.
RØDE Connect is free software that allows up to four microphones to connect with a recording interface on one computer. But, it works best with the company’s NT-USB+ mini mic which costs $100. You can find YouTube videos with advice on how to make the system work with other mics, but that will involve the use of even more apps.
For recording on a Windows platform, the free virtual audio mixer VoiceMeeter will let you hook up 2 USB mics with a control panel that has a range of different input options. The Podcast Host covers how to use the software inside Audacity.
Another option for recording with multiple mics is the original RODECaster Pro, which is a mini-production studio for around $500. It has four XLR mic inputs, a USB connection to a computer and sound effects. An upgraded version, the RodeCaster Pro II, goes for $700.
The best advice is not to overwhelm yourself by making expensive purchases but instead to learn good recording practices and techniques, which are covered in the next chapter.
Safely handling equipment became of vital importance during the pandemic and journalists reporting news from the scene took more precautions with their equipment, a good practice anytime.
You can inexpensively protect your gear by putting plastic wrap around microphones and using good ole soap and water to clean windscreens. These are safety measures that media services at colleges and universities also need to take. NPR audio engineers created a video illustrating the process.
“Reporters and producers in the field: You don’t want to wave unprotected gear in an interviewee’s face — for everyone’s sake,” says Sean Phillips.


6 Unit Operations and Material Balances
Learning Objectives
By the end of this section, you should be able to:
Define common unit operations and use these when constructing process flow sheets
Recognize the need to apply basic material balances
Common Units
We will go over four common unit types below, many other units are variants of these basic types of units.
- Mixer: has multiple feed streams and mixes these streams into one output stream
- Splitter: a splitter will split a feed stream into multiple streams with the same composition. The exiting streams are not necessarily equal in terms of flow rates, but will always have the same composition
- Separator: a separator is similar to a splitter, but has the ability to split streams into different exiting compositions
- Reactor: a reactor typically consists of a vessel in which a reaction (or multiple reactions) takes place. There are many different types of reactors, some of which you will learn more about in future courses (e.g. CHBE 376 & CHBE 355)
Processes are often represented as interconnected process units consisting of mixers, reactors, splitters, and separators among other unit operations.
Examples of other common unit operations:
- Distillation (a separation process using the difference in boiling points of components)
- Absorption (removing components from a vapour stream using a liquid) and stripping (removing components from a liquid stream using a vapour)
- Extraction (a process that purifies a dissolved substance using its solubility in two immiscible liquids)
- Heat exchanger
- Filtration
Example: Vinyl Chloride Production Process
Recall the vinyl chloride production process from the last chapter:
\begin{align*}
C_{2}H_{4} + Cl_{2} → C_{2}H_{4}Cl_{2}&\;\;\;\; (1)\\
C_{2}H_{4}Cl_{2} → C_{2}H_{3}Cl + HCl&\;\;\;\; (2)
\end{align*}
We now consider an additional reaction in the vinyl chloride production process. Most vinyl chloride manufacturers use the combination of direct chlorination and oxychlorination, which is called the balanced process .
\begin{align*}
C_{2}H_{4} + Cl_{2} → C_{2}H_{4}Cl_{2}&\;\;\;\; (1)\;\;\;\; \\
C_{2}H_{4} + 2HCl + \frac{1}{2}O_{2} → C_{2}H_{4}Cl_{2} + H_{2}O&\;\;\;\; (2) \\
C_{2}H_{4}Cl_{2} → C_{2}H_{3}Cl + HCl&\;\;\;\; (3)
\end{align*}
- Direct Chlorination (last lecture)
- Oxychlorination
- Ethylene dichloride pyrolysis (last lecture)
What is the overall reaction and what advantage does this have over what we saw last chapter?
To get the overall reaction, we add all the reactions and cancel any compounds that appear in both the reactants and products of the overall reaction. In the separation process, HCl is recycled back to the oxychlorination reactor if it is not depleted to ensure no HCl is released into the environment. Reaction (1) is balanced with the rest of the process in a way to provide the source of [latex]C_{2}H_{4}Cl_{2}[/latex] for reaction (3). This process gives us only 1 by-product: water. Using the balanced process gives us water as a by-product as opposed to hydrogen chloride.
[latex]2C_{2}H_{4}+Cl_{2}+\frac{1}{2}O_{2} → 2C_{2}H_{4}Cl_{2} + H_{2}O[/latex]
This process is carried out in multiple unit operations. To achieve the maximum efficiency and avoid releasing hazardous chemicals, hydrogen chloride produced in reaction 3 is recycled back to the oxychlorination reactor and used reaction (2), as well as unreacted EDC(ethylene dichloride, [latex]C_{2}H_{4}Cl_{2}[/latex]) in reaction 3 is recycled to react again.
- Ethylene enters the process and is split into 2 streams: 1 stream goes to the oxychlorination reactor an the other stream goes to the direct chlorination reactor
- Air and/or oxygen are fed into the oxychlorination reactor and chlorine is fed into the direct chlorination reactor
- EDC produced by both the oxychlorination and direct chlorination processes, and is fed into a purification unit to separate from the other components in the system
- EDC is then fed into the EDC pyrolysis reactor, followed by the VCM(vinyl chloride monomer, [latex]C_{2}H_{3}Cl[/latex]) purification unit, which separates HCl, VCM, and EDC into 3 separate streams
| Compound | Boiling Point ([latex]^{\circ}C[/latex]) |
|---|---|
| [latex]C_{2}H_{4}[/latex] | -103.7 |
| [latex]HCl[/latex] | -85.05 |
| [latex]Cl_{2}[/latex] | -34.04 |
| [latex]C_{2}H_{3}Cl[/latex] | -13.4 |
| [latex]C_{2}H_{4}Cl_{2}[/latex] | 83.47 |
| [latex]C_{2}H_{3}Cl_{3}[/latex] | 114 |
Separation of Components
As depicted above, we have light products (the components that are more volatile than our desired product, EDC), heavy products (the components that are less volatile than our desired product), and a stream of EDC. Let’s look at separating the components after direct chlorination:
For simplicity, say we only have chlorine ([latex]Cl_{2}[/latex]), ethylene dichloride (EDC, [latex]C_{2}H_{4}Cl_{2}[/latex]), and trichloroethane (TCE, [latex]C_{2}H_{3}Cl_{3}[/latex]) produced from a side reaction as products of the direct chlorination step. In reality, there may be other components in the stream, but we will stick to these three as the main components for this analysis. How many streams will come out after the EDC purification processes, and what are the components of each stream? How do we select the temperature for the purification process?
Compound Boiling Point ([latex]^{\circ}C[/latex]) [latex]Cl_{2}[/latex] -34.04 [latex]C_{2}H_{4}Cl_{2}[/latex] 83.47 [latex]C_{2}H_{3}Cl_{3}[/latex] 114
From the boiling point temperatures, we can deduce that the light product will be [latex]Cl_{2}[/latex] (boils at a lower temperature) and the heavy product will be [latex]C_{2}H_{3}Cl_{3}[/latex] (TCE) (boils at a higher temperature).
We can consider the separation of EDC from TCE and chlorine using 2 distillation columns. In this course, we’ll assume that distillation columns separate a single feed stream into two exit streams. There are more complex column arrangements with a greater number of entering and exit streams, but we won’t go over these in this course. Distillation columns usually operate with a range of temperatures inside them, and we’ll see why this is later in this course. For now, we’ll just assign them an average temperature.
The first column separates EDC and TCE from chlorine by operating at a temperature that is lower than EDC’s boiling temperature, but higher than [latex]Cl_{2}[/latex]‘s boiling temperature (let’s say on average [latex]60 ^{\circ}C[/latex]):
The second column separates EDC from TCE by operating at a temperature that is lower than TCE’s boiling temperature, but higher than EDC’s boiling temperature (let’s say, [latex]100 ^{\circ}C[/latex]):
Exercise: Separation Process
Consider the following vinyl chloride separation process:
The following data is available:
| Compound | Boiling Point ([latex]^{\circ}C[/latex]) |
|---|---|
| [latex]HCl[/latex] | -85.05 |
| [latex]C_{2}H_{3}Cl[/latex] (VC) | -13.4 |
| [latex]C_{2}H_{4}Cl_{2}[/latex](EDC) | 83.47 |
How would you set up distillation columns for the separation of vinyl chloride (VC) from hydrogen chloride and EDC? Provide a temperature estimate could these columns be run at for separation.
Solution
Step 1: Recognize that an easy way to separate 3 compounds is using 2 different distillation columns by separating out EDC in the first column and then separating vinyl chloride from [latex]HCl[/latex] in the second column.
Step 2: For the first column, we separate EDC as a liquid, while [latex]HCl[/latex] and vinyl chloride exit the column as gases. We choose a temperature that is lower than the boiling point temperature of EDC, but higher than the boiling point temperature of vinyl chloride. We have a large temperature range that meets these criteria, but we choose [latex]25^{\circ}[/latex] since it is an easy temperature to work with (as it is close to ambient temperatures generally).
Step 3: For the second column, we separate VC as a liquid and HCl as a gas. We choose a temperature that is lower than the boiling point temperature of VC, but higher than the boiling point temperature of HCl. For example, we may choose [latex]-50^{\circ}[/latex] .Note: this is a very cold working temperature for a distillation column and we might try to find ways to change this by manipulating pressure, but we will explore this later in this course and you will learn more through other courses.
Material Balances
General material balance rules:
- What goes in must come out (or react)
- Total mass into and out of a unit should always be equal
- Molecules or moles may not be conserved, but the atoms should be
We won’t cover material balances in-depth in this course. Instead, I will rely on you applying the concepts you are learning in your Material and Energy Balances course.
Feedback/Errata


7.7 The Labour Relations Process
Tens of thousands of American firms are unionized, and millions of U.S. workers belong to unions. Historically, the mining, manufacturing, construction, and transportation industries have been significantly unionized, but in recent years, service-based firms, including health care organizations, have been unionized.
A labour union, such as the International Brotherhood of Teamsters, is an organization that represents workers in dealing with management over disputes involving wages, hours, and working conditions. The labour relations process that produces a union-management relationship consists of three phases: union organizing, negotiating a labour agreement, and administering the agreement. In phase one, a group of employees within a firm may form a union on their own, or an established union (United Auto Workers, for example) may target an employer and organize many of the firm’s workers into a local labour union. The second phase constitutes collective bargaining, which is the process of negotiating a labour agreement that provides for compensation and working arrangements mutually acceptable to the union and to management. Finally, the third phase of the labour relations process involves the daily administering of the labour agreement. This is done primarily through handling worker grievances and other workforce management problems that require interaction between managers and labour union officials.
The Modern Labor Movement
The basic structure of the modern labour movement consists of three parts: local unions, national and international unions, and union federations. There are approximately 60,000 local unions, 75 national and international unions, and two federations. Union membership has been declining over the past three decades and is now half what it once was. The number of employed union members has declined by 2.9 million since 1983, the first year union statistics were reported. In 1983, union membership was 20.1 percent of workers, with 17.7 million union workers. In 2017, membership declined to 10.7 percent of workers, with 14.8 million members.12
A local union is a branch or unit of a national union that represents workers at a specific plant or over a specific geographic area. Local 276 of the United Auto Workers represents assembly employees at the General Motors plant in Arlington, Texas. A local union (in conformance with its national union rules) determines the number of local union officers, procedures for electing officers, the scheduling of local meetings, financial arrangements with the national organization, and the local’s role in negotiating labour agreements.
The three main functions of the local union are collective bargaining, worker relations and membership services, and community and political activities. Collective bargaining takes place every three or four years. Local union officers and shop stewards in the plant oversee labour relations on a day-to-day basis. A shop steward is an elected union official who represents union members to management when workers have complaints. For most union members, his or her primary contact with the union is through union officials at the local level.
A national union can range in size from a few thousand members (Screen Actors Guild) to more than a million members (Teamsters). A national union may have a few to as many as several hundred local unions. The number of national unions has steadily declined since the early twentieth century. Much of this decline has resulted from union mergers. In 1999, for example, the United Papermakers International Union (UPICU) and the Oil, Chemical and Atomic Workers Union (OCAW) agreed to merge under the new name of PACE, or Paper, Allied-Industrial, Chemical and Energy International Union. PACE has about 245,000 members.
Union Organizing
A nonunion employer becomes unionized through an organizing campaign. The campaign is started either from within, by unhappy employees, or from outside, by a union that has picked the employer for an organizing drive. Once workers and the union have made contact, a union organizer tries to convince all the workers to sign authorization cards. These cards prove the worker’s interest in having the union represent them. In most cases, employers resist this card-signing campaign by speaking out against unions in letters, posters, and employee assemblies. However, it is illegal for employers to interfere directly with the card-signing campaign or to coerce employees into not joining the union.
Negotiating Union Contracts through Collective Bargaining
A labour agreement, or union contract, is created through collective bargaining. Typically, both management and union negotiation teams are made up of a few people. One person on each side is the chief spokesperson. Bargaining begins with union and management negotiators setting a list of contract issues that will be discussed. Much of the bargaining over specific details takes place through face-to-face meetings and the exchange of written proposals. Demands, proposals, and counterproposals are exchanged during several rounds of bargaining. The resulting contract must be approved by top management and ratified by the union members. Once both sides approve, the contract is a legally binding agreement that typically covers such issues as union security, management rights, wages, benefits, and job security. The collective bargaining process is shown in Figure 7.9: “The Process of Negotiating Labor Agreements”.
CONCEPT CHECK
- Discuss the modern labour movement.
- What are the various topics that may be covered during collective bargaining?


Chapter 31: Stress
Lumen Learning
Causes of Stress
As a student, you’re probably plenty familiar with the experience of stress—a condition characterized by symptoms of physical or emotional tension. What you may not know is that it’s a natural response of the mind and body to a situation in which a person feels threatened or anxious. Stress can be positive (e.g., preparing for a wedding) or negative (e.g., dealing with a natural disaster).
Stress can hit you when you least expect it—before a test, after losing a job, or during conflict in a relationship. If you’re a college student, it may feel like stress is a persistent fact of life. While everyone experiences stress at times, a prolonged bout of it can affect your health and ability to cope with life. That’s why social support and self-care are important. They can help you see your problems in perspective… and the stressful feelings ease up.
Sometimes stress can be good. For instance, it can help you develop skills needed to manage potentially challenging or threatening situations in life. However, stress can be harmful when it is severe enough to make you feel overwhelmed and out of control.
Strong emotions like fear, sadness, or other symptoms of depression are normal, as long as they are temporary and don’t interfere with daily activities. If these emotions last too long or cause other problems, it’s a different story.
Signs and Effects of Stress
Physical or emotional tension are often signs of stress. They can be reactions to a situation that causes you to feel threatened or anxious. The following are all common symptoms of stress:
- Disbelief and shock
- Tension and irritability
- Fear and anxiety about the future
- Difficulty making decisions
- Being numb to one’s feelings
- Loss of interest in normal activities
- Loss of appetite (or increased appetite)
- Nightmares and recurring thoughts about the event
- Anger
- Increased use of alcohol and drugs
- Sadness and other symptoms of depression
- Feeling powerless
- Crying
- Sleep problems
- Headaches, back pains, and stomach problems
- Trouble concentrating
It’s not only unpleasant to live with the tension and symptoms of ongoing stress; it’s actually harmful to your body, too. Chronic stress can impair your immune system and disrupt almost all of your body’s processes, leading to increased risk of numerous health problems, including the following:[1]
- Anxiety
- Depression
- Digestive problems
- Heart disease
- Sleep problems
- Weight gain
- Memory and concentration impairment
That’s why it’s so important to learn healthy ways of coping with the stressors in your life.
Ways of Managing Stress
The best strategy for managing stress is by taking care of yourself in the following ways:
- Avoid drugs and alcohol. They may seem to be a temporary fix to feel better, but in the long run they can create more problems and add to your stress—instead of taking it away.
- Manage your time. Work on prioritizing and scheduling your commitments. This will help you feel in better control of your life, which, in turn, will mean less stress.
- Find support. Seek help from a friend, family member, partner, counselor, doctor, or clergy person. Having a sympathetic listening ear and talking about your problems and stress really can lighten the burden.
- Connect socially. When you feel stressed, it’s easy to isolate yourself. Try to resist this impulse and stay connected. Make time to enjoy being with classmates, friends, and family; try to schedule study breaks that you can take with other people.
- Slow down and cut out distractions for a while. Take a break from your phone, email, and social media.
- Take care of your health.
- Eat a healthy, well-balanced diet
- Exercise regularly
- Get plenty of sleep
- Try a relaxation technique, such as meditation or yoga, or treat yourself to a massage
- Maintain a normal routine
The following video features a progressive muscle relaxation meditation for you to try. There are many many others available on YouTube and elsewhere.
Video: Progressive Muscle Relaxation Meditation
If the self-care techniques listed above aren’t enough and stress is seriously interfering with your studies or life, don’t be afraid to get help. The student health center and college counselors are both good resources.
Activity: Reduce Your Stress Level
Objective
- List healthy ways of managing stress that fit your current lifestyle.
Directions
- Identify at least three things you currently do to cope with stress that aren’t working or aren’t good for you.
- Identify healthy replacements for each of them, and write yourself a “stress-relief prescription” that you plan to follow for one week. Try to include one stress management technique to use every day. At the end of the week, respond to the following prompts in a short, reflective essay (1–2 pages): Which ineffective or unhealthy coping strategies did you set out to change and why? Which stress-relief techniques did you try during the week? Were any of them new for you? Which ones were most effective? How much do you think stress affects you in your current life at college? Do you feel like you have it under control or not? If not, what else might you do to reduce your stress level?
- Follow your instructor’s guidelines for submitting assignments.
Licenses and Attributions:
CC licensed content, Original:
- Stress. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/suny-collegesuccess-lumen1/chapter/stress/ License: CC BY: Attribution
All rights reserved content:
- Progressive Muscle Relaxation Meditation. Provided by: UNH Health Services. Located at: https://youtu.be/PYsuvRNZfxE. License: All Rights Reserved. License Terms: Standard YouTube license.
Public domain content:
- Managing Stress. Provided by: CDC. Located at: http://www.cdc.gov/features/handlingstress/. License: Public Domain: No Known Copyright
Adaptions: Removed quote and images, relocated learning objectives.
- “Chronic Stress Puts Your Health at Risk,” Mayo Clinic, 2016, accessed April 27, 2018, http://www.mayoclinic.org/healthy-lifestyle/stress-management/in-depth/stress/art-20046037. ↵


KEY CONCEPTS AND SUMMARY
12.1 Why the Private Sector Underinvests in Innovation
Competition creates pressure to innovate. However, if one can easily copy new inventions, then the original inventor loses the incentive to invest further in research and development. New technology often has positive externalities; that is, there are often spillovers from the invention of new technology that benefit firms other than the innovator. The social benefit of an invention, once the firm accounts for these spillovers, typically exceeds the private benefit to the inventor. If inventors could receive a greater share of the broader social benefits for their work, they would have a greater incentive to seek out new inventions.
12.2 How Governments Can Encourage Innovation
Public policy with regard to technology must often strike a balance. For example, patents provide an incentive for inventors, but they should be limited to genuinely new inventions and not extend forever.
Government has a variety of policy tools for increasing the rate of return for new technology and encouraging its development, including: direct government funding of R&D, tax incentives for R&D, protection of intellectual property, and forming cooperative relationships between universities and the private sector.
12.3 Public Goods
A public good has two key characteristics: it is nonexcludable and non-rival. Nonexcludable means that it is costly or impossible for one user to exclude others from using the good. Non-rival means that when one person uses the good, it does not prevent others from using it. Markets often have a difficult time producing public goods because free riders will attempt to use the public good without paying for it. One can overcome the free rider problem through measures to assure that users of the public good pay for it. Such measures include government actions, social pressures, and specific situations where markets have discovered a way to collect payments.


5.10 In Summary
Erin Kelly; Sara Humphreys; Natalie Boldt; and Nancy Ami
There are people who seem to think that “good writing” is exactly the same thing as “good grammar.” We hope that by reading this chapter – as well as earlier chapters in this book – you understand why that doesn’t make much sense. Writing as an act of communication involves much more than sentence-level details of word order and phrasing and punctuation.  References to so-called correct grammar might be thought of as actually referring to “correct for this particular audience given this genre and this rhetorical situation.”
Yet grammar and style are worth paying attention to because they affect how audiences will interact with your writing. Readers expecting formal language might be turned off by colloquial phrasing. Those who don’t want to be distracted might see unusual phrasing as annoying. And those who associate formal correctness with the conventions of academic writing might not think much of your scholarly ethos if you seem not to have proofread an essay to eliminate spelling errors.
At the same time, we hope you see from some of the examples discussed here that grammar and style are also connected to much bigger ideas about writers’ identities, voices, and points of view. Skillful writers can break so-called “rules” and, in the process, make their writing even more powerful.
In sum, the reason to learn about grammar isn’t to be “correct” – it’s to empower yourself to make choices about details of your writing that get readers to pay attention to and understand what you’re trying to say.


6.5 Chapter Practice
A Multiple Sheet Template for a Sports Team
Data file: PR6 Data
You have just gotten a job with the Pacific Northwest Soccer Club, and you quickly realize that there isn’t a consistent way for all the coaches to keep track of their team statistics. To help with this, you decide to make a template for Season Stats for each team. Since you are also the coach of the High Flyers this season, you will need to use the template to enter your team’s statistics into a team spreadsheet.
- Open the data file PR6 Data and save the file to your computer as PR6 Pacific NW Sports Team.
- Copy the range B11:G22 in the Season Stats sheet to the same range in the Player Stats sheet.
- Group the sheets and add the following formulas to both sheets:
- In C22 and D22, you’ll need to count the Xs in rows 12 through 21. To do this, use a COUNTA formula.
- In E22 and F22, sum rows 12 through 21.
- In G12, calculate Goal Percentage by dividing the number of Shots by the number of Goals. This will display an error message because there are zeros in column F. We don’t want to display error messages in the file, so an IF statement that tests the value of column F will solve this problem.
- Change the formula in G12 with the following three pieces:
- Test – is F12 greater than zero
- If the Test is True – divide the number of Goals by the number of Shot
- If the Test is False – enter a zero
- Copy G12 down the column through G22. Format these cells as percentages.
- For an extra challenge, put the “banded row” format back in G12:G22.
- Ungroup the sheets.
- Save the file as a template called PR6 Pacific NW Team Template.xltx. Make sure to save your template to your USB and not the default folder for templates on your hard drive!
- Make a new file using the PR6 Pacific NW Team Template and save it as PR6 High Flyers.xlsx.
- In the Season Stats sheet, enter the following data:
- D3 – High Flyers
- D4 – Fall and the current year (i.e. – Fall 2016)
- D5 – Pacific Northwest Soccer
- Enter your name, phone number, and email address in row 8.
- Make four copies of the Player Statistics sheet. Rename the player sheets Player 1, Player 2, Player 3, Player 4, and Player 5.
- Group the Player sheets. Enter the following formulas:
- A formula in D4 that points to cell D3 in the Season Stats sheet. Note: Your formula will be =’Season Stats’!D3:G3 instead of =’Season Stats’!D3 because D3:G3 are merged together.
- A formula in D5 that points to cell D4 in the Season Stats sheet.
- A formula in D6 that points to cell D5 in the Season Stats sheet.
- Ungroup the sheets.
- Click on the Player 1 sheet. Enter the Player Name: Juan Ramirez. Enter the following data from Table 1:
Table 1: Player 1 SheetPlayed Started Shots Goals Game 1 x x 2 1 Game 2 x x 3 1 Game 3 Game 4 x Game 5 x x 2 0 Game 6 x Game 7 Game 8 x x 1 1 Game 9 x x 4 2 Game 10 x x 3 3 - Click on the Player 2 sheet. Enter the Player Name: Zach Johnson. Enter the following data from Table 2:
Table 2: Player 2 SheetPlayed Started Shots Goals Game 1 x x 1 1 Game 2 x x 2 1 Game 3 x x 1 1 Game 4 x x 1 1 Game 5 x x 2 0 Game 6 x x 5 2 Game 7 x x 4 2 Game 8 x x 1 1 Game 9 x x 4 1 Game 10 x x 3 2 - Click on the Player 3 sheet. Enter the Player Name: Vito Lawrenz. Enter the following data from Table 3:
Table 3: Player 3 SheetPlayed Started Shots Goals Game 1 x x 0 0 Game 2 x x 1 1 Game 3 x x 2 0 Game 4 x 1 1 Game 5 x x 2 0 Game 6 x x 3 1 Game 7 x x 2 1 Game 8 x x 1 1 Game 9 x x 1 1 Game 10 x x 1 1 - Make up information for the names and data in the Player 4 and Player 5 sheets.
- Go to the Season Stats sheet and click on cell C12. Enter a 3-D formula to COUNTA (count text) in C12 through sheets Player 1 through Player 5. Copy the formula in C12 through D22.
- Change the formulas in C22 and D22 to SUMs.
- Click on E12. Enter a 3-D formula to SUM E12 in sheets Player 1 through Player 5. Copy the formulas through F22.
- Preview the worksheets in Print Preview. Notice that only part of the data is printing for each worksheet. This is because a Print Area was incorrectly set when the file was first created. You need to clear this Print Area for each worksheet individually (modifying print areas cannot be done on grouped sheets). Exit Backstage View and for each worksheet, click the Print Area button on the Page Layout tab and select Clear Print Area.
- Save the PR6 High Flyers workbook.
- Compare your work with the self-check answer key (found in the Course Files link) and then submit the PR6 High Flyers workbook and PR6 Pacific NW Team Template as directed by your instructor.
Attribution
” 6.5 Chapter Practice” by Diane Shingledecker, Portland Community College is licensed under CC BY 4.0