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38670 results in Cambridge Textbooks

Page 1250 of 1934

  • Preface

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp xvi-xviii

  • Summary

    Why I Wrote This Textbook

    Every year one of my social psychology lectures holds my students’ attention more than any other. My students are rapt, at times laughing, at times seemingly astounded at the story I am telling. What is this lecture about? The topic is Clark and Hatfield's (1989) article on receptivity to sexual offers. In this experiment, Clark and Hatfield had research assistants approach students of the opposite sex on campus and randomly ask one of three questions: “Would you go out tonight?” “Will you come over to my apartment?” or “Would you go to bed with me?” Clark and Hatfield found that a majority of men but not a single woman agreed to have a “sexual liaison” with the person who approached them (p. 39). I will admit that my students do not act in quite the same way for all my lectures. Why is this lecture different? Developing a relationship is something that virtually all have experienced or want to experience. This research is relevant to the students’ lives, and it is exciting. I found myself wondering: Why not make all of this early research exposure relevant and exciting?

    Thus, this textbook uses research relevant to students’ lives to illustrate research methodology. Every major research approach in psychology is covered. Students will learn how to evaluate and use different varieties of descriptive research and experimental research methods. They will learn all steps of the research process from coming up with a research idea to writing about and presenting what they did. Through it all, the one constant is that information is presented within the confines of the familiar: the students’ own lives.

    This textbook is likely to be of interest to instructors who teach undergraduate research methodology courses that are not discipline-specific. The students and instructor potentially will have a range of discipline interests, but all of the students likely have the “student life” interest in common. This textbook could also be of interest to instructors in research methods courses that focus on social psychology, for many of the research examples come from the social psychology discipline.

  • Chapter 14 - Writing About and Presenting Your Research

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp 337-369

  • Summary

    If a tree falls in the forest and no one is around to hear it, does it make a sound? I never liked that question, but I do like an analogous one: If you do research and you never tell anyone about it, have you contributed to science? I know the answer to that one! The answer is no. We have a responsibility to disseminate our research, to tell others what we have done and what we have found, so that together we can move toward finding answers to our questions.

    There are a few different ways to disseminate information about our research. We can present a paper or a poster at a conference, and we can publish our work. We'll cover all these approaches in this chapter.

    The sixth edition of the Publication Manual of the American Psychological Association (APA, 2010) governs the way we present our work (see Figure 14.1), and so we will refer to the relevant sections of the APA Publication Manual throughout this chapter. If you have questions regarding APA style that are not addressed here, you can consult the current Publication Manual or the APA style blog (blog.apastyle. org). Tutorials showing the basics of APA style are also available at the APA website (www.apa.org).

    We'll start by looking at how a psychology research paper is organized.

    The Organization of a Psychology Research Paper

    A typical psychology research paper will contain the following sections:

  • 1. Title page

  • 2. Abstract

  • 3. Introduction

  • 4. Method

  • 5. Results

  • 6. Discussion

  • 7. References

  • 8. Tables and figures (these are optional).

    • As we progress through this chapter, I will cover the kind of information contained in each section. Later, we will talk about the specific formatting of each section, and you'll see examples of the different sections of a research paper, which will be annotated so you can see exactly where and how different information is represented. At this stage, while you are writing the paper, it's called a manuscript. Writing in APA style is a learned skill that takes practice. Reading through this chapter and referring to the sample manuscript in Appendix A will help you write your own manuscript.

  • 7 - Membrane Trafficking: Flow and Barriers Create Asymmetries

  • from Part II - Design and operation of complex functions
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 145-165

  • Summary

    There are two distinct systems involved in the establishment of membranecompartmentalized functions in cells. Synthesis and secretion are involved in producing new materials, whereas endocytosis and recycling are involved in metabolism and turnover. Both are involved in the sorting of components for maintaining the compartments. In the synthetic pathway, it is critical for cells to move membranes from the site of protein and lipid synthesis to the correct membrane compartments. In the endocytic pathway, endocytosis of the plasma membrane brings in components from the environment that are sorted and processed for cell growth and activity. These functions rely upon two major mechanisms to move membranes from one compartment to another, either vesicle fission/fusion or fusion of membranes and flow followed by fission. The material to be transported is selected by coat proteins or other filters. The endocytic and synthetic pathways involve bidirectional flows of material that sort components for recycling or forward transport. In the endocytic pathway, most endocytosed components are rapidly recycled, while some are processed before recycling, and an even smaller fraction are degraded. In the synthetic pathway, the ER synthesizes the whole volume of the cellular membranes in a day for a typical growth rate (higher rates are found for specialized secretory cells). Newly synthesized membrane proteins are typically glycosylated in the ER and moved to the Golgi for further glycosylation before transport to either secretory vesicles, lysosomes, or peroxisomes. Flow through these pathways can be likened to liquid flow between a series of pools in that the inhibition of the inflow will cause shrinkage and of the outflow will cause expansion of the pool. Membrane bending stiffness, bilayer asymmetry and tension all play significant roles in membrane trafficking and the proteins involved are designed to sense and respond to each one of these membrane factors. In terms of robust systems engineering, the dynamic membrane system is designed to create linked compartments for sequential processing of proteins either as part of synthesis or metabolism.

    Membrane dynamics is critical for many functions, including secretion, renewal, nutrient supply, and signaling. Cells have the capacity to transport large amounts of membrane and perform sorting operations that confine many components to a compartment while selectively removing others for further processing. Normally the transport mechanisms are robust, and this enables tasks to be performed, albeit at a slower rate, even when one or another protein sorting system is lost.

  • 5 - Inter-State Arbitration

  • from PART I - FOUNDATION OF INTERNATIONAL DISPUTE SETTLEMENT
  • Yoshifumi Tanaka, University of Copenhagen
  • Book:
    The Peaceful Settlement of International Disputes
    Published online:
    21 June 2018
    Print publication:
    11 January 2018, pp 105-127

  • Summary

    Main Issues

    Arbitration is one of the legal means of international disputes. An arbitral tribunal is established in an ad hoc manner on the basis of the consent of the parties in dispute and its decisions are binding upon the litigating parties. Arbitration is flexible compared to standing international courts and tribunals in the sense that the parties to a dispute can retain considerable control over the process of arbitration. Among various types of arbitration, this chapter will focus on inter-State arbitration. In particular, the following issues will be examined:

  • (i) What are the principal features of inter-State arbitration?

  • (ii) What are the problems associated with the selection of arbitrators?

  • (iii) What is the standard to determine the independence and impartiality of arbitrators?

  • (iv) What are the reasons that may deprive the validity of an arbitral award?

  • (v) What is the advantage of arbitration and what are its limitations?

    • INTRODUCTION

    As provided in Article 15 of the 1899 Convention for the Pacific Settlement of International Disputes, ‘[i]nternational arbitration has for its object the settlement of differences between States by judges of their own choice, and on the basis of respect for law’. While, at present, multiple types of arbitration exist in the international community, this chapter will focus on inter-State arbitration.

    Like judicial settlement, the results of arbitration are legally binding upon the parties to the dispute. In this regard, arbitration is distinguished from diplomatic means of international dispute settlement. However, arbitration is distinct from judicial settlement in five respects (see Table 5.1).

  • (i) A composition of arbitral tribunals: While judicial settlement concerns international dispute settlement by pre-constituted international courts and tribunals, arbitrators are to be chosen by parties to a dispute on a case-by-case basis. Accordingly, the parties in dispute can control the composition of an arbitral tribunal. This procedure contributes to strengthening the confidence of the parties. Normally an arbitral tribunal is composed of three or five or, at most, seven members. The relatively small size of the arbitral organ makes the arbitration procedure simple and speedy. The preference for a more restricted tribunal might also have an advantage in case of more technical disputes.

  • 10 - Peaceful Settlement of International Environmental Disputes

  • from PART II - INTERNATIONAL DISPUTE SETTLEMENT IN PARTICULAR FIELDS
  • Yoshifumi Tanaka, University of Copenhagen
  • Book:
    The Peaceful Settlement of International Disputes
    Published online:
    21 June 2018
    Print publication:
    11 January 2018, pp 311-333

  • Summary

    Main Issues

    International disputes concerning environmental protection arise in various contexts of international relations. As there is no single judicial body specialised for the settlement of international environmental disputes, the issues of environmental protection are to be addressed by multiple judicial bodies, such as the ICJ, ITLOS and WTO panels, if these disputes cannot be resolved by diplomatic means. Furthermore, to protect the environment effectively, it is necessary to secure compliance with the obligations provided in environmental treaties. In this regard, non-compliance procedures set out in multilateral environmental treaties are crucial as an alternative dispute resolution. This chapter will seek to examine the following issues:

  • (i) What are the principal features of peaceful settlement of international disputes concerning environmental protection?

  • (ii) What is the role of international adjudication in the peaceful settlement of international environmental disputes and what are its limitations?

  • (iii) What is the role of the Treaty Commission in the peaceful settlement of international environmental disputes?

  • (iv) What is the difference between the non-compliance procedures and traditional means of international dispute settlement?

    • INTRODUCTION

    International disputes concerning environmental protection are arising in multiple contexts, such as the regulation of trans-frontier air pollution, the use of international watercourses, the regulation of marine pollution, the exploration and exploitation of natural resources, and international trade and commerce. In light of the diversity of issues relating to environmental protection, it is difficult and even illusory to define an ‘international environmental dispute’. For the purposes of this chapter, an environmental dispute is broadly understood as a dispute which includes an environmental aspect.

    In light of the increasing importance of environmental protection, including protection of natural resources and biological diversity, disputes will more frequently arise with regard to the interpretation and application of relevant rules of international law on this subject. Hence the peaceful settlement of international environmental disputes should be a crucial issue in international law. Following the introduction, this chapter analyses the role of international courts and tribunals in the settlement of international environmental disputes (section 2). It then examines the role of fact-finding commissions established in environmental treaties (section 3). Furthermore, this chapter moves on to address non-compliance procedures set out in multiple environmental treaties (section 4), before offering conclusions (section 5).

  • 6 - Engineering Lipid Bilayers to Provide Fluid Boundaries and Mechanical Controls

  • from Part II - Design and operation of complex functions
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 119-144

  • Summary

    Membranes form the boundaries of cells. In eukaryotic cells, membranes also create internal organelles that are critical for compartmentalizing cell functions and making the system more robust (note, from textbox below, that 95–98% of cell membrane mass is internal). As physical boundaries, they define the cell and organelle volumes and must be moved in cell motility and membrane trafficking. As chemical boundaries, they keep critical components in the cytoplasm and other factors outside the cytoplasm and possibly the cell. The hydrophobic barrier provided by lipid bilayers blocks movement of charged and hydrophilic substances into and out of the cell. An important robust property of cells is that plasma membranes can often be lysed multiple times before a cell will die. They serve a gateway function in that they need to facilitate entry of some components and the exit of others. Also, chemical and physical elements of the cellular microenvironment, including its architecture, need to be communicated to the cytoplasm. Cell shape is typically defined by the cytoskeleton for most mammalian cells, but membrane area to cell volume ratio affects the shape as well as the mechanical properties of the membrane. Membrane mechanics play a critical role in many cytoplasmic as well as cellular phenomena because cell membranes have a significant bending stiffness and resistance to stretch as well as a fluid nature.

    Membranes as Compartment Boundaries

    The basic role of membranes is to compartmentalize cells by blocking the free diffusion of water-soluble components. Biological membranes are organized around lipid bilayers that have a hydrophobic core and two hydrophilic surfaces. Hydrophobic molecules and surfaces cause an increase in the order of water by not forming hydrogen bonds and creating a surface like an air–water interface. Because order causes a decrease in entropy, the hydrocarbon layer of the bilayer separates readily from water by hiding in the center of the bilayer, making the bilayers quite stable. Breaking a bilayer and exposing the hydrophobic edges to water is energetically very unfavorable. For this reason, holes in bilayers reseal rapidly to cover the exposed hydrocarbon tails. Many membrane proteins extend across the bilayer and they have a hydrophobic surface that fits with the hydrophobic domain of the bilayer. The specific transport of ions and certain molecules by transmembrane proteins occurs through hydrophilic channels in those proteins (Chapter 8).

  • 4 - Cells Exhibit Multiple States, Each with Different Functions

  • from Part I - Principles of complex functions in robust machines
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 69-94

  • Summary

    We are well aware that organisms exhibit different states of awareness, from sleep to heightened tension. Cells can likewise be in different states (phases) where different response networks and different functions are active. The different phases of the cell cycle are obvious examples of how the same cell can exhibit different behaviors when stimulated in a defined way without changing its differentiation state. Furthermore, a given function may have different activators and different levels of activity in different phases. Thus, it is important to control the cell phase when studying any given function. With a large population of cells in a variety of cell phases, the assay of a function will potentially give a mixture of activity levels. There are many different possible phases for cells, including changes in type of motility or metabolic activity in addition to the well-characterized phases of the cell cycle, senescence, or apoptosis. It is important to consider how the cell decides to transition from one phase to another. As was discussed in the previous chapter, the inability of a cell to complete a desired function can be a stimulus to change to an alternative pathway that can involve a change in phase. Further, phase changes can also be induced by the internal cell clock, or external stimuli. Another issue is that widely different cell types can exhibit very similar phases (e.g. mitosis is similar for different types of cells). Thus, many of the characteristic functions associated with different phases are present in many cell types but need specialized conditions to become activated. The same function may have varied outputs in different cell types, but the basic elements would be common to all cells. Often the transitions between phases occur in a very short time and constitute a concerted change. The probability that cells in a population will be in the same phase can be controlled in the lab using patterned substrates and defined conditions. However, single-cell studies can provide a better understanding of the cell phase when a given subcellular function is analyzed. Using defined molecular markers for specific phases, it is possible to follow phase changes at a single-cell level in multicellular tissues.

  • Chapter 6 - Correlational Research

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp 134-156

  • Summary

    In Chapter 5, you saw that sometimes, instead of manipulating what our study participants see and experience, we use non-experimental methods; we just observe our participants in their natural environments without influencing them at all. In these cases, we are using descriptive research methods. The lack of control in descriptive research methods means that we do not have the ability to establish cause and effect.

    The correlational research approach, a popular research method, is another non-experimental research approach. In correlational research, we measure different variables to see whether there is a relationship between or among them. In other words, you would have a relationship between measured variables if they vary systematically together (as intelligence rises, does academic performance rise as well?). I'll explain more about this below. Before we go on, remember that since correlational research is another descriptive research technique, we cannot use it to investigate whether one variable causes another.

    The Basic Differences between Experimentation and Correlational Research

    Before we talk about the details of correlational research, I'd like to explain the basic methodological differences between experimentation and correlational research.

    Experimentation

    Consider the simplest kind of experiment. It has one independent variable with two levels represented by two groups with different people in each group. Here are the steps we take in a simple experiment:

  • We randomly assign participants to the two groups.

  • We manipulate (vary) an independent variable. Say we give one group 2 oz. of caffeine and the other group 10 oz.

  • We measure a dependent variable, say performance on a math test.

    • There are indeed advantages to doing experimental research; number one is the ability to establish cause and effect (as explained in Chapter 1). Unfortunately, there are times when we cannot do highly controlled experiments due to practical or ethical concerns. Take the following example:

  • • Does illegal drug use during their college years increase students’ risk of having difficulties in college?

    • We cannot randomly put study participants into two groups, and give one group illegal drugs and not give illegal drugs to the other group; this would be unethical. Whether a student takes illegal drugs is not a decision that is up to experimenters. To investigate these types of questions, researchers instead often turn to correlational research.

  • Chapter 2 - Developing Research Ideas and Hypotheses

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp 31-54

  • Summary

    When I was a first-year graduate student, I had to write a research proposal for one of my psychology classes. I was supposed to propose something original, something no one had ever done before (since most of the research that gets published is original, my professor thought I should get used to thinking of these kinds of ideas). I had a very difficult time choosing a topic to study. It seemed that all the original ideas were taken!

    I've since realized that if you want to do original research, you don't need to find a big new idea; you just need to do something that's at least a little bit different from what's been done before (although big new ideas are good too!). In this chapter I'll tell you how to generate research ideas. We'll begin by exploring the following potential sources of research ideas as shown in Figure 2.1 :(1) real life, (2) practical problems, (3) previous research, and (4) theory.

    Sources of Research Ideas

    Have you ever come across an item in the news or in your own life that made you wonder about why things happen? Perhaps you won't be surprised that real life is a primary source of ideas for research.

    Real Life

    I recently read a story about two girls in Australia who got stuck in a storm drain. Luckily they had their cell phones with them, but instead of calling the police or someone they knew, they updated their Facebook status! Someone finally saw it and called the police.

    Thankfully the girls were not injured, but a police officer later acknowledged that they would have been helped much sooner had they called the police directly (Malkin, 2009). This story led me to wonder: Is social media use so prevalent among young people that they would likely rely on that as a way to reach out to others instead of just making a phone call? At this point we have the beginning of a research idea: Use a survey to ask people about their social media use (see Chapter 7 for more information on surveys). But before you go and conduct this study, or any study actually, you need to find out what researchers already know about the topic.

  • Chapter 5 - Descriptive Research Methods

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp 109-133

  • Summary

    In the first chapter you were introduced to different types of research methodologies. In an experiment, as you'll recall, you vary what you present to different groups of study participants, and then you see how the different groups are affected by your manipulation. But in some situations, it would be extremely difficult or even unethical to do an experiment. So instead of manipulating what our study participants see or experience, we observe them in their natural environments and describe what we see.

    Let's consider an example. What if I were interested in the behavior of people who are saying goodbye to each other at an airport? Could I reasonably study this within the laboratory? That would certainly be difficult; airport behavior is probably best studied in the airport with a form of descriptive research. That's what we are going to discuss in this chapter: descriptive research methodology.

    All descriptive research methods have one thing in common; they are non-experimental methods. We are observing and describing what we see; we are not manipulating anything. Since we do not have control over what our participants experience, we cannot draw definitive conclusions about what is influencing their behavior. Thus, none of these descriptive methods gives us the ability to establish cause and effect.

    Despite their inability to help us establish cause and effect, descriptive research methods can be an effective way to explore a topic researchers do not yet know much about. Once our observations allow us to become more familiar with the topic, we can work toward making predictions and developing a theory to explain our observations.

    In this chapter we will cover four types of descriptive research methods: (1) naturalistic observation, (2) participant observation, (3) archival research, and (4) case studies. We'll start with naturalistic observation.

    Naturalistic Observation

    In naturalistic observation you observe people (or animals) in their natural settings and systematically record their behavior. In fact, there are many natural settings for people. Just think about where you are during your everyday life: school, library, gym, park, office, restaurant, stores. Observing people in their natural settings can provide important information about the way they behave.

  • Chapter 3 - Ethics

  • Wendy Heath, Rider University, New Jersey
  • Book:
    Psychology Research Methods
    Published online:
    01 July 2021
    Print publication:
    11 January 2018, pp 55-82

  • Summary

    When I was an undergraduate and taking a research methods course, I was stunned to learn about a study conducted by Middlemist, Knowles, and Matter (1976). What did Middlemist et al. do? They wondered whether invading people's personal space in a college men's room would cause arousal and in turn affect the timing of the observed men's urination (how long before they started urinating, and how long they spent urinating).

    So they set up a situation in which males would enter a public restroom with three urinals and be forced to use the urinal on the left. This allowed for a situation in which there was a confederate either at the urinal right next to the study participant or one urinal away (a control condition was also used in which no one was present at a urinal when the participant entered the restroom). An observer positioned in a stall used a periscopic prism to view the stream of urine. Upon hearing of the periscope, I remember thinking, “Wait, what?! Can they do that?”

    Sure, the results were interesting: invading people's personal space in the bathroom did affect how long it was before the men started urinating, and it affected the amount of time they spent urinating. But was this study ethical? Welcome to the chapter on ethics, where we'll review the specifics that govern researchers’ ethical responsibilities and answer the question, “Can they do that?”

    A Brief History of Research Ethics

    History is unfortunately littered with examples of research in which humans were subjected to gross mistreatment. Many suffered and even died as a result of such mistreatment. We'll consider a couple of these cases in an effort to illustrate how research ethics have evolved over time.

    The Nuremberg Code

    After World War II, physicians who had worked for the Nazis went on trial in Nuremberg, Germany for crimes committed against prisoners of war. The details of these crimes were horrific as these physicians deliberately tested the limits of human endurance. For example, they placed people in ice water to see how long it would take them to freeze to death. They shot people with poison bullets. They placed them in chambers that allowed the Nazis to test people's responses to high-altitude conditions (Harvard Law School Library: Nuremberg Trials Project).

  • 15 - Turning RNA into Functional Proteins and Removing Unwanted Proteins

  • from Part II - Design and operation of complex functions
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 324-340

  • Summary

    Most proteins in a cell are synthesized in close proximity to the nucleus through a process known as ‘translation,’ in which ribosomes translate mRNA into protein following its export from the nucleus. Proteins that will be secreted or integrated into membranes must be processed within the endoplasmic reticulum (ER). This requires a signal sequence that enables the docking of the ribosome to the ER. During translation, the protein is moved into the lumen of the ER, where it will be processed. Other mRNAs are targeted for transport to selected regions of the cytoplasm or for sequestration until proper signals are received. The number of proteins synthesized from a single mRNA is highly variable, but is usually in the range of 100–1000 copies. The subsequent lifetime of the protein depends largely upon whether it is properly synthesized. Defective, misfolded proteins, or proteins that are no longer required, will be actively removed from the cytoplasm. This is achieved through a process of ubiquitinylation, which flags the protein for degradation by a proteasome. This process is dependent upon the activation of ubiquitin ligases that are downstream in a number of signaling pathways. Both localized protein synthesis and targeted degradation can facilitate cellular functions by dramatically altering the concentrations of proteins at critical times.

    Protein production is truly the hallmark of life as we know it, as proteins form the machinery that performs most cellular functions. As such, the translation of mRNA into protein is an extremely sophisticated process and one can imagine that virtually every mutation of the proteins in the ribosome and in the ribosomal RNA have been tested by cells or organisms. Any improvements would be shared with other organisms and, thus, the current ribosomes should be viewed as particularly robust. In this chapter, we will first discuss the actual process of protein production and the sophisticated adaptations for larger eukaryotes, including localized synthesis, protein folding, and processing. Protein degradation is the balance to synthesis and is used to rapidly block functions as well as to remove denatured proteins or recycle proteins in starvation conditions. Assuming proper nutrient levels, the goal of protein production and turnover is to provide the cell with the tools needed to perform the differentiated cell functions as well as face many environmental challenges from hyperthermia and trauma to various bacterial and viral challenges.

  • 7 - Digital Hearing Aids

  • Andrew G. Webb
  • Book:
    Principles of Biomedical Instrumentation
    Published online:
    11 August 2019
    Print publication:
    11 January 2018, pp 196-234

  • Summary

    Introduction

    Roughly 10% of the world's population suffers from some form of hearing loss, with over 5% or 360 million individuals suffering from hearing impairment that is considered to be disabling by World Health Organization (WHO) standards. The most common cause of hearing loss is damage to the cochlea, which results in reduced frequency selectivity and associated blurring of complex sounds. According to statistics compiled by the National Institute on Deafness and Other Communication Disorders (NIDCD) approximately 2 to 3 out of every 1000 children in the United States are born with a detectable level of hearing loss in one or both ears. One in eight people in the United States aged 12 years or older has hearing loss in both ears. Approximately 2% of adults aged 45 to 54, 8.5% aged 55 to 64, 25% aged 65 to 74, and 50% of those 75 and older have disabling hearing loss. Figure 7.1 shows the frequency and temporal characteristics of human speech, as well as the loss in different frequency ranges and classification of hearing loss from mild to profound.

    Among people aged 70 and older who could benefit from hearing aids, only ~30% have ever used them, and the percentage for younger adults is significantly lower. The main reasons are the physical visibility of the device (related to social issues), the need for manual adjustments and problems in sub-optimal conditions such as strong winds and distracting background sounds (technical issues). In order to address the societal issue hearing aids are continually being designed to be smaller, with many of the miniaturization techniques outlined throughout this book enabling the reduction in size. Technical issues are being addressed via new developments in both hardware design as well as more powerful signal processing software. Each of these developments presents design challenges in terms of the requirement to package an ever-greater number of electronics in a more limited space, and to ensure that these electronics can operate in a power-efficient manner so as to maintain long battery life.

    This chapter outlines the basic design of digital hearing aids, and the principles behind these designs [1]. The first sections in this chapter consider the physiology and acoustic properties of the human auditory system, the causes of hearing loss and the basics of hearing-aid design.

  • 1 - Robust Self-replicating Machines Shaped by Evolution

  • from Part I - Principles of complex functions in robust machines
  • Michael Sheetz, Columbia University, New York, Hanry Yu, National University of Singapore
  • Book:
    The Cell as a Machine
    Published online:
    06 August 2018
    Print publication:
    11 January 2018, pp 3-24

  • Summary

    Biological cells are wonderfully robust self-replicating machines that selfishly propagate their DNA until environmental factors such as nutrients limit them. Cells have mastered the use of nanoscale devices in a water environment to fabricate their progeny and perform many critical functions for survival. To understand how cellular machines work, we need to understand the identity and structure of molecular components as well as the network of interactions between these molecules. We also need to study the complex cell functions in which an orchestra of molecules interacts transiently in space and time to cause an observable cellular behavior. Such an integrated systems engineering view of the cell is currently far from our reach; however, there are sufficient tools and techniques in place to provide us with many useful insights into the complex functions of the wonderful machines that are cells.

    In this book, we will mainly discuss eukaryotic cells and where possible the details of mouse embryo fibroblasts (3T3 cells) and a human cancer line (HeLa). Because there are over 300 different cell types with important specializations, we have chosen a relatively general cell type to describe what cells do. Many complex functions are missing in fibroblasts and there will be some necessary extrapolations at certain points. 3T3 and HeLa cells do not form multicellular tissues; cell–cell interactions and the higher-order functions of tissues will be discussed in later chapters. The level of integration and complexity needed for the control of multicellular complex functions is at least an order of magnitude greater than for single cell complex functions. We first focus on dissecting the individual complex functions in single cells, because it is then possible to analyze multicellular complex functions in a modular fashion.

    In this chapter, we will define the biological cell that we wish to understand and discuss how evolution has made it more robust over the last two billion years (Huxley, 1958). A cutaway diagram of a cell in suspension (Figure 1.1) provides an illustration of the basic organelle compartments that are found in mammalian cells. Compartmentalization of functions is critical for a complex machine like a cell. Each compartment performs some basic function(s) and communicates bidirectionally with the rest of the cell. Often compartments, like the cell itself, are bounded by lipid bilayers, whose hydrophobic cores effectively prevent open movements of ions and charged materials into or out of the compartments.

Page 1250 of 1934