Research into Consumer Behaviour
Declaration of originality I hereby declare that this project was entirely my own work and that any additional sources of information have been duly cited. I hereby declare that any internet sources, published or unpublished works from which I have quoted or drawn reference have been reference fully in the text and in the contents list. I understand that failure to do this will result in failure of this project due to Plagiarism. I understand I may be called for a viva and if so must attend. I acknowledge that was my responsibility to check whether I am required to attend and that I will be available during the viva period. ABSTRACT Consumer behaviour is a factor that is given a lot of importance in the marketing world. The launch of any product can result in its success or failure depending on the manner in which consumer behaviour is analysed and the extent to which consumers are motivated. Food being a basic necessity of mankind has a huge market potential especially with the organic food. Consumers are becoming increasingly dissatisfied with GM (Genetically Modified) and conventional food. Therefore there is an inclination seen towards the organic food sector in the market. Organic food is said to be healthier due to ethical ways of production which do not use man-made chemicals and unnecessary preservatives as opposed to conventional food. It is also said to be eco-friendly because of environment conscious methods which are used for the production of organic food. The advantages of organic food are more whereas the disadvantages (such as price premium) are negligible when compared to its better side. Regular buyers of organic food are willing to overlook these minor disadvantages which are negligible. In this research work, the consumer behaviour in the United Kingdom (UK) regarding organic food is studied and compared with that in India. The factors (such as consumer expectations, beliefs, criteria, concerns, quality, awareness and so on) that affect marketing of organic food in the UK and in India are also studied with relevance to consumer behaviour. In the United Kingdom, organic food market is majorly divided whereas the Indian market is growing at a faster pace. The growing demand for organic foods from the consumers because of its quality, safety and positive environmental impacts have increased the demand among the consumers. The research has contributed good knowledge of the various factors that can depict the future organic food consumer trends in the United Kingdom and in India. Some of the main factors like the consumer demographic. Apparently this has enabled to outline certain challenges that may assist in improving the current marketing strategy for organic food in India. Suggestions were also given in the later part of the dissertation that can change the present marketing scenario and would inevitably encourage more consumers to decide on buying organic food. ACKNOWLEDGEMENTS First and foremost I would like to thank god for giving me immense strength and courage to complete this dissertation and my parents for empowering their blessings throughout this dissertation. Secondly, I would like to extend my gratitude to Simon Speller, my supervisor who was always enthusiastic and motivated me to complete my dissertation. I wish to express my warm and sincere gratitude towards him who encouraged and guided me throughout my research study. I would like to thank specially my Module leader Yi Zhu, who encouraged me and never hesitated to help me out during my study. I immensely thank my friends especially Taj and Tinoy and the employees of the stores who were always there to lend me their hand. CHAPTER 1: INTRODUCTION This study is focused on the consumer behaviour and to understand their approach towards organic food in the United Kingdom and in India. Organic food has a healthier demand because of its better quality, taste and appearance. Brunso (2002) denotes that since the organic food is healthier and the process of making it is more convenient, consumers will easily accept these merits. Consumer lifestyle has been noted as one of the factors for the consumers to make certain preferences and organic food is better prevailing among consumers since people are more focused on a healthy lifestyle. They prefer organic food since it is healthier, fresher, tastier, residue free and eco-friendly. It is nutritional and tastier and the process of producing the organic food is not harmful to the environment when compared to conventional food Lang, (2005). When the consumers see the label organic, they presume that the product is of superior quality because of the way it is processed. The use of natural raw materials, welfare oriented animal husbandry and eco-friendly usages of land are the aspects regarded by a consumer. According to an organic consumer, the word organic implies quality which means unadulterated ingredients which is favourable to the consumers likewise the production process is also safer to the environment which comprises of the wellbeing of the humans, animals and plants. On the whole it is beneficial to the community and the universe (Beck et al., 2006). Conventional foods are produced using pesticides, fertilizers, ionizing radiation and they are dependent on soil and water polluting methods. Hence consumers are prepared to pay more for organic food which is of residue free. Virtually all non-organically produced foods contain residues of pesticides, fertilizers and other chemicals, and to prevent the consumption of these infirmity consumers buy organic food which is tastier and nutritious. According to the Consumer reports, since 1996 pesticides which were formerly used extensively are now federally banned and restricted by some manufacturers to meet safety standards in particular for the children Dabbert, Haering,
Santa Monica College Julie Barmazels Criticism on Macbeth Discussion
professional essay writers Santa Monica College Julie Barmazels Criticism on Macbeth Discussion.
I’m working on a english question and need a sample draft to help me study.
These are the guidelines:GoalOpinion/AssertionPostRead the criticism in this module [below], entitled, “The Servant to Defect: Macbeth: Impotence and the Body Politic” and share your ideas about the criticism in a discussion post (you MUST quote the passage). The post is meant to be a response specifically to THIS CRITICISM. So write at least three full paragraphs [or more if you wish] on this criticism [in relation to the play] for the full 20 points. GradingClick on the rubric to see how the discussion will be graded. (Links to an external site.)“The Servant to Defect: Macbeth, Impotence, and the Body Politic”Julie Barmazel “Th’ attempt and not the deed/ Confounds us.”Lady Macbeth (2.2.10–11)1 The question of the Macbeths’ children—or lack thereof—has given a number of recent critics cause to contemplate Lady Macbeth’s potentially vexed relationship with menstruation and childbirth, her role as a madwoman or hysteric moved to murderousness by the vagaries of her womb as well as those of her mind.2 Alice Fox, in particular, has noted that “a major function of the imagery of obstetrics and gynecology in Macbeth” is to make us “aware of the protagonists as human beings who want to have children . . . as human beings whose desire for living children has been frustrated” (“Obstetrics” 138). Indeed, the play returns relentlessly to images of bodily frustration and inadequacy, especially with regard to reproduction, evidencing what Gail Paster has characterized as a typically early modern preoccupation with “bodily refinement and exquisite self-mastery” (14)— both of which the Macbeths apparently lack. Such frustration with the body, evoking fears of the inability to master one’s sexual and/or reproductive functions, speaks to a profound anxiety about physiology characteristic of the Renaissance imaginary: Shakespeare’s was an age, Paster reminds us, “newly preoccupied with corporeal self-discipline” (10) and deeply influenced by the notion of the humoral body, the idea that the body operated fundamentally as a storehouse of unwieldy fluids that determined one’s temperament.3 This body was thought to have very much a mind of its own: “Humoral physiology ascribes to the workings of the internal organs an aspect of agency, purposiveness, and plenitude to which the subject’s own will is often decidedly irrelevant” (Paster 10). For early moderns, that is, the body was viewed increasingly as a site of shameful unruliness, in which corporeal imbalance would likely determine one’s state of mind and course of action (or inaction). Through the metaphor of the body politic, the workings of the body could also be used to understand the state of the state. As Gil Harris has argued, [t]o an extent that has not been fully acknowledged, early modern English versions of organic political analogy are similarly fixated with illness: extensively informed by the emergent discourses of Renaissance physiology, nosology, and pathology, elaborate accounts of the body politic’s sundry diseases and their remedies make their first appearance in the literature of the period. Political writers, playwrights, and pamphleteers attempted to explain . . . the nature of the corpus politicum’s ills (Harris 3).Macbeth can be viewed productively as one such text, as a play in which the frailties and imbalances of the body are made to speak to state ills, and vice versa. And while it has become a commonplace to view theater as “one of the Renaissance’s most powerful and most ubiquitous mechanisms for explain- ing and enforcing political structure” (Raber 299), I would redirect our attention to the ways Shakespeare’s play also does the reverse: to the playwright’s tendency to characterize political structures as both inheriting and reflecting the body’s infirmities—weaknesses over which the subject may have disturbingly little control. If, as Frank Whigham has suggested, “during the early seventeenth century Renaissance drama increasingly presented the body politic in privacy [and] Elizabethan political and social sins once portrayed with armies and rebels and maps were often recast in terms of sexual deviation and bodily excess” (Whigham 333), then Macbeth illustrates the extent to which its playwright is also concerned with the body’s role in public politics; with the primacy of the private(s), as it were. And while the play opens with references to scenes of bloody battle, it reads for the most part as a tragedy of a highly personal, bodily, and domestic nature, in which the intrapersonal stakes are raised to the status of state business and state business is understood primarily in terms of the body—and the marital bed. Although a good deal of critical attention has been paid to the potentially physiologically inflected language of Lady Macbeth’s speeches, the play’s numerous allusions to her husband’s physiology have remained largely under-explored. In this chapter, I would like to (re)turn our gaze to Macbeth’s problematic body by looking at the play’s elaborate network of puns about and allusions to Macbeth’s sexual dysfunction. These work to connect the fruitlessness of Macbeth’s political aspirations with those of his body, ironic- ally making both images more potent. Macbeth’s political sterility—his pointless destructiveness, his lack of political heirs—reenacts and confirms the sterility of his bed chamber; his power-lust is depicted in terms of poorly managed bodily lust and a related imbalance of bodily fluids. In short (and I use this term pointedly), Macbeth is impuissance embodied, and I shall devote the rest of this chapter to underscoring the many ways in which the play suggests a link among his physical, political, and moral disequilibria. Such connections resonate with those made by James I and other writers of the period, who saw kingship as bound up fundamentally with fatherhood, and fatherhood with bodily mastery: for James, “a king is truly Parenspatriae, the politic father of his people,” and is “rightly compared to a father of children, and to a head of a body composed of divers members” (“A Speech to the Lords and Commons of the Parliament at Whitehall  and “The True Law of Free Monarchies , cited in Carroll 216–17).5 As Alexandra Shepard has noted, “although domestic advice dwelt extensively on men’s mastery of others, it also emphasized that this was predicated on their mastery of themselves” (77–78). Masculine self-governance, in turn, was intimately linked with the management of bodily fluids: as Mark Breitenberg has suggested, early moderns possessed a model of normative humoral masculinity in which the body’s fluids are carefully (and anxiously) regulated according to what is allowed to enter and what must be expelled and in which all members of the body act properly in accordance with their assigned places and designated functions—an idealized vision of the masculine body as well as utopian political state.(Breitenberg 38–39) If, as Shepard has said of the early modern period, “[t]he self-government expected of manhood was the basis of men’s claims to authority” and “[m]en could not govern others if they were unable to govern themselves” (70), then Macbeth’s inability to master his sexuality and/or impregnate his wife implies that he is also incapable of legitimately fathering a nation. (In the words of Sir Robert Filmer [c.1630], “there is no monarchy, but paternal” [cited in Stallybrass 131].) This would have been particularly pleasing to James I, who traced his lineage to Malcolm and Fleance:6 the more “unnatural” Macbeth’s sexuality appears, that is, the more “natural” the lines of descent from Malcolm and Fleance to James I come to seem. Among a cast of principals who appear either as parents or children or both, it has often been noted, the Macbeths stand alone as childless and un(re)productive: Duncan is at once the father of a nation and of Malcolm and Donalbain; Banquo is aligned throughout the drama with his son Fleance; Macduff with his wife and precocious son; and the elder Siward with Young Siward. While the drama revolves around what Shakespeare calls in his tenth sonnet the making of “another self,” or procreation, only the Macbeths, the Weird Sisters, and the Three Murderers lie outside the circle of generation, in the “unnatural” realm of explicit self-interest and unapologetic self- promotion, where a lack of offspring hints at a concomitant lack of concern for the well-being of society at large.The marked contrast between the fruitfulness of the play’s major—and law-abiding—figures and the barrenness of the Macbeths encourages questions: Why are the Macbeths alone without heirs? “Or who is he so fond will be the tomb/ Of his self-love to stop posterity?” (Sonnet 3). Has the pair’s lack of children generated their present self-absorption, or vice versa? Have they in fact chosen not to reproduce, or has their fate been determined by their physiology? By the end of the first act it is clear that Lady Macbeth’s current state of childlessness is not likely due to any incapacity to bear children on her part. She has, after all, “given suck, and know[s]/ How tender ’tis to love the babe that milks me” (1.7.54–55). We are made to understand from this speech that Lady Macbeth has mothered a child.8 Had she, then, a previous husband? Did her babe, or possibly babes, die during infancy? Such speculation, encouraged by both the structure and language of the play, leads to further questions still:9 What of Macbeth’s role in the marriage’s current state of childlessness? Is Macbeth incapable of reproducing, or has he become so estranged from his wife that they no longer expect intimacy? The couple’s closeness at the start of the play would indicate the contrary: before the Macbeths’ bloodlust changes them so much as to make their personalities almost unrecognizable, the two clearly function in concert, something made obvious both by the content of Macbeth’s letter to his wife in Act 1 and by the fact of his having written to her immediately after having heard the “perfectest report” of the Weird Sisters (1.5.2). She is his “dearest partner of greatness” (1.5.9–10), his “dearest chuck” (3.2.45), and theirs appears to be a far from loveless marriage.Given such intimacy, and in light of Lady Macbeth’s comments about having nursed an infant in the past, the play seems to suggest that the responsibility for any reproductive problems the couple might have lies squarely with Macbeth—and this despite the dominant early modern belief that “ barrenness was . . . the fault of the woman” (Pollock 41).10 Lady Macbeth’s explicit preoccupation with her body, and the suggestive language through which she expresses this concern, help to underscore the notion that she is (or at least believes herself to be) all too fertile, too womanly; so much so that she must call upon the gods to “unsex” her if she is to commit murder (1.5.39)— an act that, to the early moderns, was decidedly masculine.11 The play’s implicit references to menstruation reinforce the notion that Lady Macbeth is entirely too much dominated by her fertility, her female physiology, her “nature,” to commit the “unnatural” act of murder:12 in a drama blood- soaked from the start, Lady Macbeth is—to her frustration—steeped not only in the innocent blood of her victims, but in her own menstrual blood, the bodily issue that indicates both the possibility of giving birth and the (temporary) death of this opportunity, the very condition that defines the Macbeths and their “unlineal” rule. Lady Macbeth is still susceptible to the “compunctious visitings of nature” (1.5.43), to use the colloquial Renaissance term for menstruation, and would have the spirits “make thick my blood” and “Stop up th’access and passage to remorse” (1.5.41–42), which is to say that her blood has not been “stopped-up” and that the reproductive capacity she spurns is still very much extant within her.13 So, too, is the quality of mercy that was thought to have attended it, and that will—by way of remorse— eventually lead to her madness.14 Thus, while Macbeth refers to his wife’s (masculine-inflected) “undaunted mettle” (1.7.73), we also sense that he protests too much. The “masculine” vigor and violence with which Lady Macbeth attempts to renounce her body indicate that it possesses an equally strong “femininity,” a femininity that is, ironically, the worthy opponent of her malevolence—in large part because of its reproductive capacity and fluids. Macbeth’s fearful, half-critical, half awe-filled urging that his wife “[b]ring forth men-children only” (1.7.72) further underscores Lady Macbeth’s reproductive potential, while simultaneously distancing Macbeth from the process of generating heirs himself. His comment almost suggests a fantasy of will- ful parthenogenesis on the part of his wife: it implies that Lady Macbeth alone might assume responsibility for creating (and possess the power to produce) her own issue—and to decide its sex, no less—while Macbeth’s language clearly places him on the periphery of the process, passive and inconsequential.Such irrelevance will characterize Macbeth’s reign, as well. And through- out the play, the king’s ultimate political inconsequentiality—his inability to produce heirs who might legitimate and extend his reign—is made to resonate with the language of bodily insufficiency, with the suggestion that Macbeth is unable to extend himself physically, at least when it comes to pleasing his wife. He appears in the play surrounded, variously, by the language of sexual insufficiency and inadequacy (or “unmanned” manhood [3.4.73]) and masturbatory excess—both of which would have arguably connoted humoral imbalance to a Renaissance audience.15 If Lady Macbeth is too wet to commit murder, in other words, her husband is depicted as too dry to act the part of the proper man—in large part, we suspect, because he has already drained himself “dry as hay” (to paraphrase the curse of the First Witch in 1.3.17). In Act 3, for example, Macbeth claims that his “strange and self-abuse/ Is the initiate fear that wants hard use” (3.4.142–43). While these lines are usually taken to mean that Macbeth sees himself as an insufficiently hardened criminal, as one who has allowed his fears about immoral acts to lead him to hallucinate, the phrases “hard use” and “strange and self-abuse” may have possessed masturbatory overtones.16 Like the subject of Shakespeare’s first sonnet, Macbeth, too, apparently “feeds’t [his] light’s flame with self- substantial fuel,/ Making a famine where abundance lies.” Or, as Hecate says directly on the heels of Macbeth’s comment, Macbeth “loves for his own ends” (3.5.13)—a pronouncement that resonates with Macbeth’s own description of “a barren scepter in my gripe/ Thence to be wrenched with an unlineal hand,/ No son of mine succeeding” (3.1.63–65), and his assertion: “strange things I have in head, that will to hand” (3.4.139). Lady Macbeth’s “compunctious visitings” would have served as a monthly reminder of her husband’s shortcomings in this regard: because his “will” is in his hand, rather than her body, she will continue to bleed instead of becoming pregnant. “Yet here’s a spot . . . Out, damned spot! Out, I say! One, two. Why, then, ’tis time to do’t,” she famously says (5.1.27–31). Might not Lady Macbeth’s horror at these imagined bloodstains reenact the monthly reminder that she is not yet with child—a reminder still audible in her insistence that it is, once again, “time to do’t”? Finally, if some of Macbeth’s own lines may be supposed to have had masturbatory implications, then so too might Angus’s suspicion that Macbeth “does . . . feel/ his secret murders sticking on his hands” (5.2.16–17).Terms denoting sterility, and possibly connoting masturbation, abound in this play—and why not? The Macbeths’ is, after all, a masturbatory reign, insofar as its end is only to satisfy the couple’s (political) desires, without a concern for the future of the nation. Macbeth’s “will”—signifying both his political ambitions and his member—is, of course, mishandled; is insufficient to the task at hand. Macbeth speaks of having “no spur/ To prick the sides of my intent” (1.7.25–26), but the implication is that this “rat without a tail”— to paraphrase the First Witch again—actually has no “prick” to use with his wife. His member is his first disobedient subject. The Porter’s innuendo- riddled speech about drunken impotence, given just after Macbeth murders the king and just before he returns to the scene to face Duncan’s sons, thus serves as more than a brief comic interlude in the midst of profound horrors; it strikes directly at the heart of the matter of the play. Drink, the porter says, gives one the desire for sex while removing the means, making one unable to “stand to.” In Macbeth’s words, “Our will became the servant to defect,/ Which else should free have wrought” (2.1.18–19). Shakespeare indicates that Macbeth has been singularly unable to master his body, and by implication will fail to master the body politic. Again, political and bodily terms are conflated—so much so that Shakespeare even has his would-be king envision his ascent to the throne in terms of penile sufficiency: on the heels of the Weird Sisters’ prophesy, Macbeth muses over what he describes as “the swelling act/ Of the imperial theme” (1.3.127–28), suggesting a link between the act of becoming king and the ability to maintain an erection. This line also speaks to the Captain’s earlier description of Macbeth’s adventures in battle: “So from that spring whence comfort seemed to come/ Discomfort swells,” he says (1.2.27–28). We are, in other words, encouraged to associate Macbeth with a dysfunctional member—a defunct spring—from the start of the play, and to view his rise to kingship as an unnatural attempt to shore up the masculinity that he himself has weakened. Lady Macbeth will eventually reinforce this image by accusing her husband of “unbend[ing]” his “noble strength” (2.2.48), implying that both Macbeth’s political aspirations and his sex have been mishandled.19 Macbeth, in turn, associates his ultimate commitment to murderous deeds with a working penis: “I am settled,” he says in response to his wife’s demands, “and bend up/ Each corporal agent to this terrible feat” (1.7.79–80). The line implies that Macbeth sees murder as a means of “bend- ing up” his “corporal agent,” as a way to have in marriage what he has only recently had in battle: “cannons over-charged with double cracks,/ So they doubly redoubled strokes upon the foe” (1.2.37–38). Lady Macbeth has cer- tainly implied that her husband’s “cannon” has not been “overcharged” of late, nor “stroking” at all, let alone “doubly.” Bearing in mind that “courage” had indicated “lustiness” and “vital force” since at least the fifteenth century and “sexual vigour and inclination” since at least the mid-sixteenth (Oxford) English Dictionary 3), Lady Macbeth’s insistence that her husband “screw [his] courage to the sticking-place” (1.7.60) also serves as a less-than-subtle reminder of his usual failure in this regard.Lady Macbeth’s oft-cited aspersions against her husband’s manliness thus have a distinct materiality. The would-be queen’s rhetoric suggests that Macbeth’s physical, emotional, and political weaknesses are unthinkable in isolation—and that each must be corrected if the couple’s desires are to be satisfied. Lady Macbeth’s promptings seem designed as a spur to a man who has none, as a means to seeing her husband finally endowed by virtue of being enthroned, and vice versa. All of this is necessary, she suggests, because her husband’s “nature . . . is too full o’th’milk of human kindness/ To catch the nearest way” (1.5.14–16), too full of womanly humor to carry out its requisite functions. Again, bodies and wills collide in Shakespeare’s language. “Nature” connotes menstrual blood, as well as the female genitalia;22 the “milk of human kindness” that supposedly fills Macbeth’s “nature” betokens a range of female bodily fluids (menstrual blood, mother’s milk), but at the same time also suggests semen (OED 2b). Macbeth is thus both too much a woman and too little a man. He is saturated with the bodily fluids associated with childbearing, but without the children that should, to a Renaissance mind, accompany them.Lady Macbeth’s charges do not refer merely to Macbeth’s metaphorical “womanliness” or slack effeminacy, then, but to what she characterizes as a distinctly physical/sexual inadequacy, as well. “Are you a man?” she taunts. “What, quite unmanned in folly?” (3.4.58 and 73).24 Lady Macbeth makes clear that her opinion of her husband depends very much on Macbeth’s proving that he is not, ultimately, to be “unmanned”: . . . From this timeSuch I account thy love. Art thou afeardTo be the same in thine own act and valour,As thou art in desire? . . .When you durst do it, then you were a man. And to be more than what you were, you would Be so much more the man. (1.7.38–51) Again, political ambitions are allied with sexual desire and ability. Bearing in mind the bawdy implications of the First Witch’s “I’ll do, I’ll do, and I’ll do” (1.3.9), Lady Macbeth’s “When you durst do it, then you were a man” reinforces her already strong case against Macbeth’s potency (i.e. he hasn’t yet “done it” with her) while simultaneously highlighting the couple’s working assumption that Macbeth’s identity is dependent on his sexual proficiency, on his ability to manage his member properly.25 Thus, while commentators some- times encourage us to think of Macbeth’s murderousness as “in part an act of love done to please his wife” (Wintle and Weis 143), his actions are perhaps better viewed as the desperate behavior of an “unmanned” man than they are those of a simply doting, even uxorious, husband. The marriage that first appears to us as supportive and collaborative turns out to be based on—or perhaps to have devolved into—an “unnatural” alliance in which the “masculine” female is forced to compensate for her husband’s physical insufficiency: “Infirm of purpose!” she accuses him, “Give me the daggers” (2.2.55–56). It is because Macbeth’s dagger is infirm, in other words, and because he has kept hold of it, that his wife must make such a demand. By this point in the play, it is clear that the Macbeths equate the king’s ability to rule with his ability to master his sex. Not surprising, then, that Macbeth should describe his murder of Duncan in terms of sexual conquest, equating his approach to the king with that of Tarquin to Lucrece (2.1.55), and proclaiming after the murder that he has finally “done the deed” (2.2.14).26 Perhaps more importantly, he has attempted to prove to himself that he can truly make good use of his dagger. The tragedy of Macbeth, of course, is that his daggers (his knife, his member) are misused, and thus lead only to destruction without increase, to a (not so) petit mort that fails to provide what should “naturally” follow: the planting and growth of Macbeth’s seed.Given the logic of sex and death—or climax without result—that guides Macbeth, it is fitting that the drama should repeatedly invoke the specter of orgasm, as well. The term “come”—which the OED notes appeared in print with its present connotation of reaching orgasm in 1650 (17), and which, I suggest, would have held that meaning for Shakespeare at the start of the century—appears in Macbeth’s speeches and in speeches relating to him with a noticeable regularity: “Macbeth doth come” (1.3.29); “Come what come may” (1.3.145); “our thane is coming” (1.5.32); “Come, let me clutch thee,” he says to the vision of the dagger (2.1.34); and “To bed, to bed; . . . Come, come, come, come, give me your hand . . . to bed, to bed, to bed” (5.1.56–58) his wife says to him in her reverie. The witches sing “Come away, come away” (3.5) after discussing the fact that Macbeth, perhaps a man whom they have already decided to “drain . . . as dry as hay” (1.3.17) and who “loves for his own ends” (3.5.13), will “come to know his destiny” (3.5.17). A common enough word, but it appears almost too often in Macbeth. Perhaps this is because the doomed king has already “come” too much—but to no good end—or because he will never come into his own, as it were. Perhaps the witches are implying that Macbeth must “come” in order to fulfill his destiny, while Lady Macbeth urges him to do what she knows all too well he cannot. “The cry is still ‘They come!’ ” (5.5.2), Macbeth says of his enemies as the play ends, in a comment that at once announces the presence of Malcolm, Siward, and Macduff and reminds us of the fundamental difference between Macbeth and the rightful heirs to their titles. Malcolm has already hinted at this discrepancy, in the account of his own character that he gives Macduff: Malcolm. I grant [Macbeth] bloody, Luxurious, avaricious, false, deceitful, Sudden, malicious, smacking of every sinThat has a name. But there’s no bottom, none,In my voluptuousness: your wives, your daughters, Your matrons, and your maids could not fill up The cistern of my lust, and my desireAll continent impediments would o’erbear,That did oppose my will. Better MacbethThan such an one to reign. (4.3.57–66) The suggestion is that Macbeth represents the antithesis of Malcolm’s putative sexual prowess. If “Better that your wives, your daughters,/ Your matrons, and your maids” should be unsafe in Malcolm’s presence than that they should be ruled by one who poses no sexual threat whatever—whether he be “luxurious” (i.e. lustful) or no. Taken as a whole, the play illustrates precisely the dangers of having such a one as king. Together, Shakespeare’s myriad allusions to Macbeth’s sexual dysfunction promote the idea that his marriage has been as sterile as will be his reign, and as terminal. The material and the marital thus speak to the martial and the monarchical. In her longest speech about Macbeth, Hecate says “There hangs a vap’rous drop profound;/ I’ll catch it ere it come to ground” (3.5.24– 25), indicating that Macbeth’s seed will never germinate, that, in contra- distinction to Banquo, Macbeth will not be “planted,” will not be “full of growing,” as Duncan says Banquo will be (1.4.28–29). For all of Macbeth’s coming, then, he never arrives, his self-love remaining always his goal and obstacle, and leading, finally, to his undoing. In the end, Macbeth loses the scepter he had never learned to hold on to properly (despite, or because of, his many attempts to do so), and, in a final emasculating blow that lends itself to these sorts of readings, loses his head as well, making explicit the condition that we have already been led to imagine throughout the body of the play.
Santa Monica College Julie Barmazels Criticism on Macbeth Discussion
Strategic Goals Within The Automobile Industry Management Essay
This Report looks the performance of Firm C against strategic goals within the automobile industry. We will be looking on how Firm C has used the strategic principles and theories in order to compete with other six automobile firms in same industry. Basing on the areas of study we can see how Firm C has managed to utilize the resources. Using simulation technology over a number of weeks the company used market information to inform strategy and monitor performance. In retrospect, as this report concludes, much more informed decision-making processes and governance would have assisted in ensuring the performance of the company and achievement of the mission of Firm C. However through this simulation game, individuals have managed to relate the theory they have learnt in class and apply them in the really field. “A company’s strategy is management’s game plan for growing the business, staking out a market position, attracting and pleasing customers, competing successfully, conducting operations, and achieving targeted objectives.” (Thompson, Strickland and Gamble 2005, p 3) As described Thompson, Strickland and Gamble (2005) who explained that for a company to have a sustainable competitive advantages, needs to have a differentiated products with features such as added performance , high quality and wider product choices. This is what Firm C tried to achieve by reducing cost of production so that the price of cars should go down, the reasons for this is to get to a wide range of customers. Therefore, the firm concentrate on the price sensitive category, value seekers, customers with more disposable income and fairly price sensitive customers. Strategy Thinking One of Firm C’s strategies was to have a “first mover” advantage. This can be defined as: an organisation that moves down the experience curve by getting into a market first should be able to reduce its cost because of the accumulated experience it builds up over its rivals by being first. (Thompson, Strickland and Gamble 2005) Firm C has done this by being one of the first firms to produce a new concept car and by being the only firm to focus more on quality and safety. Adopting the Boston Matrix, Kotler and Keller (2006), the company used market feedback to place products in the market into the appropriate categories and used this to inform investment decisions. Using market data (consumer and external trading conditions) the company contextualised their strategic decisions by understanding customer needs, available market spend and trends linked to the overall economy, such as affordability and luxury. One key strand to ensuring high performance was focusing the models produced on a core market, but to provide a number of models. This approach allowed a diversification of products without overstretching the company’s range of products. This, in turn, would allow for marketing to focus on the core offerings of the products. Through focusing on the core market, and limited development of new products, whilst maximizing plant capacity and marketing, it was considered to be part of the long term strategy to offer a return to investors and increase the value of the company without compromising customer perceived valued of the products and brand. Short-Term versus Long Term Considerations All decision -taken on these six periods was to ensure the company is doing well in car manufacturing industry and keeps on meeting customers expectations. This would give a company to have efficient production and hence result to profit maximization. The Short-term investment in product development allowed minor upgrades to come to market quicker in response to customer demands for safety and quality above luxury. No long-term decisions were taken at the immediate outturn whilst the company assessed the long-term prospects. The long term was taken when there was a necessary change in what customers prefer and in order to go together with the technology changes. Firm C has one of the highest technology capabilities in terms of interior, quality and styling with the highest technology capability than any other firm in the StratSim world to produce safe cars. This is one reason that has made Firm C to have competitive advantage over other firms in StratSim world which has set our cars to be safest over all cars. Mission
The Transmission Electron Microscopy Biology Essay
The Transmission Electron Microscopy Biology Essay. The transmission electron microscope operates on the same basic principles as the light microscope but uses electrons instead of light. What you can see with a light microscope is limited by the wavelength of light. TEMs use electrons as “light source” and their much lower wavelength make it possible to get a resolution a thousand times better than with a light microscope. TEM uses a technique whereby a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera. TEMs are capable of imaging at a significantly higher resolution than light microscopes, owing to the small de Broglie wavelength of electrons. This enables the instrument’s user to examine fine detail-even as small as a single column of atoms, which is tens of thousands times smaller than the smallest resolvable object in a light microscope. TEM forms a major analysis method in a range of scientific fields, in both physical and biological sciences. TEMs find application in cancer research, virology, materials science as well as pollution, nanotechnology, and semiconductor research. History of TEMs The first operational electron microscope was presented by Ernst Ruska and Max Knoll in 1932, and 6 years later Ruska had a first version on the market. In 1986 Ruska received a Nobel Prize in physics for his “fundamental work in electron optics and for the design of the first electron microscope”. The following table gives a basic outline of the history of the electron microscope by decades. Year Specimens Application/development Instrumentation/theory Resolution 1940s Replicas oxide carbon plastics surfaces slip steps extracted particles fractography -50kV, single condenser -little or no theory; a first basic theory of electron microscopy was published in 1949 by Heidenreich. ~10nm 1950s Thin foils: from bulk deposited defects phase transitions -100kV -contrast theory developed. ~0.5-2nm 1960s metals semiconductors ceramics minerals Dynamic in-situ studies substructure of solids radiation damage microdiffraction -high voltage electron microscopes (Toulouse: 1.2 and 3MeV) -scanning electron microscopes -accessories for in-situ studies -controlled experiments 0.3nm (transmission) ~15-20nm (scanning) 1970s catalysts quasicrystals High resolution imaging lattice imaging -Analytical transmission electron microscopy -scanning transmission electron microscopy -energy dispersive x-ray spectra -electron energy loss spectroscopy -commercial high voltage electron microscopy (0.4-1.5MeV) -high resolution imaging theory 0.2nm (transmission) 7nm (standard scanning) 1980s virtually all materials atomic resolution in close-packed solids surface imaging small particles -commercial medium-voltage high-resolution/analytical electron microscopy (300-400kV) -improved analytical capabilities -energy filtering imaging -ultra-high vacuum microscopes 0.15nm (transmission) 5nm (scanning at 1kV) 1990s fast computation for image simulation alloy design nanostructures integrated digital scanning and image processing -surface atomic microscopy -orientation imaging microscopy 0.1nm (transmission) 3nm (scanning at 1kV) 2000s Electron microscopy in the 1960s In 1969 RCA dropped out of the electron microscope business, having decided that they could make more money selling record albums and consumer electronic devices. General Electric had never become a major power in the electron microscope business. This left the field wide open for companies such as JEOL, Hitachi, and Akashi in Japan, and Philips, Siemens, and Zeiss in Europe. The resolution of the best TEMs was now approximately 0.3 nm (3 Å); JEOL claimed a resolution of 0.2 nm (2 Å) for its 1968 model JEM-100B. Accelerating voltages were still typically in the 100 kV range, although JEOL marketed a 200 kV instrument in 1967 called the JEM-200. Philips marketed a very popular 100 kV microscope called the EM 300 in 1966. They claimed that this was the ‘first fully-transistorized electron microscope,’ and that it could attain a point resolution of 0.5 nm (5 Å). More than 1,850 units of the EM 300 were sold. Another approach to the study of materials that emerged in the 1960s involved increasing the accelerating voltage of the electron gun to extreme levels up to 3 MeV in an effort to penetrate more deeply into thicker samples. CEMES-LOE/CNRS at Toulouse, France, developed a 3MeV instrument around 1965, followed closely by JEOL, which released a 1 MeV microscope, the JEM-1000, in 1966. (One MeV represents a million electron volts, while one kV is a thousand electron volts. So 1,000 kV= 1 MeV.) These ultrahigh voltage EMs were so large that they typically occupied their own two-story building. The electron gun and its associated high voltage electronics were located near the ceiling of the second story, while the operator sat at the bottom of the microscope column looking at the fluorescent screen. Hitachi’s 1964 model HU-500 stood 4 meters tall; later, higher MeV versions eventually made this look small. On the left is a photograph of the 1 MeV Atomic Resolution Microscope (ARM) at the Lawrence Berkeley Laboratory. Electron microscopy in the 1970s The 1970s were a time of rapid development on all fronts in the electron microscope industry. Further improvements in TEM came from brighter electron sources (lanthanum hexaboride and field emission guns). The resolution of the TEM was pushed to 0.2 nm (2 Å) in the 1970s, with better results reported in some cases for lattice imaging resolutions; Hitachi claimed a 1.4 Å lattice resolution for its 1975 model H-500 TEM, and JEOL claimed the same resolution for its 1973 model JEM-100C. Accelerating voltages of 100 kV maximum had become the norm. In contrast to the low cost instruments, Philips 1972 model EM 301 TEM was designed for high performance and versatility for the skilled operator who had the time to coax the best results from his instrument. The EM 400 introduced in 1975 used a LAB6 electron gun, which was ten times as bright as the standard tungsten filament at the time. On the down side, the reactivity of lanthanum hexaboride required an ultra-clean vacuum system of 10-6 Torr. In 1977 Philips introduced accessories for the EM 400, including a secondary electron detector for topographical studies and a field emission gun (FEG) a single crystal tungsten tipped filament that emits electrons from a very localized region of the tip to produce narrow, bright electron beams. FEGs can have100 to 1,000 times the brightness of a LAB6 filament, with electron beam diameters as small as 1 nm. Vacuum requirements for these FEGs are 10-10 Torr. JEOL started with the JEM-100B Analytical model in 1970, which added scanning ability and an EDX x-ray spectrometer to the TEM. This was improved upon by the JEM-100C in 1973, with its 1.4 Å resolution, and further upgraded by the JEM-100CX Analytical model in 1976, which added an ultraclean vacuum system and a LAB6 electron gun. In the ultrahigh voltage EM market, The Hitachi 3MeV HU-3000 was installed at Osaka University in 1970. This accelerating voltage was the highest ever for an electron microscope. A resolution of 4.6 Å was reported for this instrument. The 1976 model H-1250 had a maximum voltage of 1250 kV, but a superior resolution of 2.04 Å. Electron microscopy in the 1980s During the 1980s TEM resolutions were further reduced to 1.0 to 1.5Å, making imaging of atoms in lattice planes possible. Microprocessor control of microscopes and computerized analysis of data became common due to the emergence of the personal computer in the early 80s. This microprocessor control brought about such features as an auto-stigmator and auto-focus, freeing the microscope operator from the mundane tasks that had always been involved in using the instrument. Electron energy loss spectroscopy (EELS) detectors were incorporated in STEMs and AEMs, allowing detection of low atomic number elements that could not be seen using x-ray techniques. The demands of the fast-growing integrated circuits industry produced electron microscopes designed for non-destructive testing of semiconductor wafers and for functional testing of ICs. Smaller electron beam sizes made it possible to switch from microprobe to nanoprobe technology. Elemental mapping of a sample’s surface could now be done on a nanometer level. Development of low cost instruments was not a priority in the 1980s. Some that were developed in the 1970s continued to be sold, but development was focused on high-performance, high-resolution, microprocessor-controlled instruments. JEOL produced 7 new TEM units between 1980 and 1986. These included the JEM-1200 EX (1981), which added microprocessor control to the JEM-100 CX (1976). The same model equipped with an EDS x-ray spectrometer was called the JEM-1200 EX/Analytical microscope. The 1984 model JEM-2000 FX/Analytical had a maximum voltage of 200 kV and a resolution of 2.8 Å; this instrument marked the switch from a microprobe beam to a nanoprobe. The JEM-4000 FX/Analytical microscope introduced in 1986 raised the acceleration voltage to 400 kV, which produced a beam probe size only 2 nm in diameter. After years of a standard 100 kV accelerating voltage with a few ultrahigh voltage units thrown in, these medium-voltage microscopes finally became popular. Electron microscopy in the 1990s The 1990s produced several corporate mergers in the electron microscope industry. Carl Zeiss and Leica joined to form LEO Electron Microscopy, Inc. In 1996 Philips bought Electroscan, the developer of the environmental SEM in the 1980s, to form Philips Electroscan. The following year Philips Electron Optics and a company called FEI merged under the name FEI to continue manufacturing electron microscopes. Hitachi and JEOL remained independent entities. The resolution of TEMs had already reached its theoretical limit (the best possible resolution predicted by calculations), so the 1Å resolution obtained using field emission gun (FEG) electron sources remained the standard. Medium voltage range instruments up to 300 kV were common, although 100 kV instruments still kept their long lasting popularity. Computers were now a vital part of every electron microscope, with graphical user interfaces (GUIs) being the norm. They were involved in both the control of the instrument and the processing of data, including post-analysis enhancement of micrographs using contrast-enhancing software. JEOL offered TEMs with maximum accelerating voltages of 120, 200, and 300 kV. The 120 kV model JEM1230 had a resolution of 0.2 nm (2Å). The JEM-2010 F FasTEM (200 kV) and the JEM-3000 F FasTEM (300 kV) both used FEG sources and achieved resolutions of 0.1 nm (1.0 Å). Three meetings of the Electron Microscopy Society of America (1968, 1975, and 1980) The Electron Microscopy Society of America (now known as the Microscopy Society of America) was founded in 1942, when it began holding annual meetings for instrument makers and users to gather and discuss the technology and its applications. The topics of papers given at these meetings present a snapshot of the state of electron microscopy at the time. A brief look at three of these meetings shows the evolution of the technology and its applications over a 12-year period. In the brief twelve-year span of 1968 to 1980, the physical sciences overtook the biological sciences at EMSA meetings, judging solely on number of papers presented. A large part of this development is probably due to the emergence of the scanning electron microscope in 1965, which made examination of the surface of bulk specimens possible for the first time. Since physical scientists could now look at “real” samples instead of replicas or thin films, activity in microscopy of materials increased dramatically. With no similar dramatic development in biological microscopy, the balance shifted. The Science of TEMs Comparison of Light (LM) and Electron Microscopes. a. Similarities 1) Illumination system: produces required radiation and directs it onto the specimen. Consists of a source, which emits the radiation, and a condenser lens, which focuses the illuminating beam (allowing variations of intensity to be made) on the specimen. 2) Specimen stage: situated between the illumination and imaging systems. 3) Imaging system: Lenses which together produce the final magnified image of the specimen. Consists of i) an objective lens which focuses the beam after it passes through the specimen and forms an intermediate image of the specimen and ii) the projector lens(es) which magnifies a portion of the intermediate image to form the final image. 4) Image recording system: Converts the radiation into a permanent image (typically on a photographic emulsion) that can be viewed. b. Differences 1) Optical lenses are generally made of glass with fixed focal lengths whereas magnetic lenses are constructed with ferromagnetic materials and windings of copper wire producing a focal length which can be changed by varying the current through the coil. 2) Magnification in the LM is generally changed by switching between different power objective lenses mounted on a rotating turret above the specimen. It can also be changed if oculars (eyepieces) of different power are used. In the TEM the magnification (focal length) of the objective remains fixed while the focal length of the projector lens is changed to vary magnification. 3) The LM has a small depth of field, thus different focal levels can be seen in the specimen. The large (relative) depth of field in the TEM means that the entire (thin) specimen is in focus simultaneously. 4) Mechanisms of image formation vary (phase and amplitude contrast). 5) TEMs are generally constructed with the radiation source at the top of the instrument: the source is generally situated at the bottom of LMs. 6) TEM is operated at high vacuum (since the mean free path of electrons in air is very small) so most specimens (biological) must be dehydrated. 7) TEM specimens (biological) are rapidly damaged by the electron beam. 8) TEMs can achieve higher magnification and better resolution than LMs. 9) Price tag!!! (100x more than LM) Figure below shows the cross-sectional view of a standard TEM. Figure shows the transmission electron microscope at The Chinese University of Hong Kong. Figure shows a schematic outline of a TEM. A TEM contains four parts: electron source, electromagnetic lens system, sample holder, and imaging system. A. Electron Source The electron gun produces a beam of electrons whose kinetic energy is high enough to enable them to pass through thin areas of the TEM specimen. The gun consists of an electron source, also known as the cathode because it is at a high negative potential, and an electron-accelerating chamber. There are several types of electron source, operating on different physical principles, which we now discuss. i. Thermionic Emission Figure 3-1 shows a common form of electron gun. The electron source is a V-shaped (“hairpin”) filament made of tungsten (W) wire, spot-welded to straight-wire leads that are mounted in a ceramic or glass socket, allowing the filament assembly to be exchanged easily when the filament eventually “burns out.” A direct (dc) current heats the filament to about 2700 K, at which temperature tungsten emits electrons into the surrounding vacuum by the process known as thermionic emission. Figure 3-1. Thermionic electron gun containing a tungsten filament F, Wehnelt electrode W, ceramic high-voltage insulator C, and o-ring seal O to the lower part of the TEM column. An autobias resistor, RB (actually located inside the high-voltage generator, as in Fig. 3-6) is used to generate a potential difference between W and F; thereby controlling the electron-emission current, Ie. Arrows denote the direction of electron flow that gives rise to the emission current. Raising the temperature of the cathode causes the nuclei of its atoms to vibrate with increased amplitude. Because the conduction electrons are in thermodynamic equilibrium with the atoms, they share this thermal energy, and a small proportion of them achieve energies above the vacuum level, enabling them to escape across the metal/vacuum interface. The rate of electron emission can be represented as a current density Je(in A/m2) at the cathode surface, which is given by the Richardson law: Where T is the absolute temperature (in K) of the cathode and A is the Richardson constant (~106Am-2K-2), which depends to some degree on the cathode material but not on its temperature; k is the Boltzmann constant (1.38 x 10-23J/K), and kT is approximately the mean thermal energy of an atom. ii. Schottky emission The thermionic emission of electrons can be increased by applying an electrostatic field to the cathode surface. This field lowers the height of the potential barrier (which keeps electrons inside the cathode) by an amount, the so-called Schottky effect. A Schottky source consists of a pointed crystal of tungsten welded to the end of V-shaped tungsten filament. The tip is coated with zirconium oxide (ZrO) to provide a low work function (~2.8 eV) and needs to be heated to only about 1800 K to provide adequate electron emission. Because the tip is very sharp, electrons are emitted from a very small area, resulting in a relatively high current density ( Je ~ 107A/m2) at the surface. Because the ZrO is easily poisoned by ambient gases, the Schottky source requires a vacuum substantially better than that of a LaB6 source. iii. Field emission If the electrostatic field at a tip of a cathode is increased sufficiently, the width (horizontal in Fig.3-4) of the potential barrier becomes small enough to allow electrons to escape through the surface potential barrier by quantum-mechanical tunneling, a process known as field emission. The probability of electron tunneling becomes high when the barrier width, w is comparable to de Broglie wavelength of the electron. This wavelength is related to the electron momentum p by p=h/Î» where h= 6.63 x 10-34 Js is the Planck constant. Because the barrier width is smallest for electrons at the top of the conduction band, they are the ones most likely to escape. Because thermal excitation is not required, a field-emission tip can operate at room temperature, and the process is sometimes called cold field emission. As there is no evaporation of tungsten during normal operation, the tip can last for many months or even years before replacement. It is heated (“flashed”) from time to time to remove adsorbed gases, which affect the work function and cause the emission current to be unstable. Even so, cold field emission requires ultra-high vacuum (UHV: pressure ~ 10-8 Pa) to achieve stable operation, requiring an elaborate vacuum system and resulting in substantially greater cost of the instrument. B. Electromagnetic Lens System The TEM may be required to produce a highly magnified (e.g, M = 105) image of a specimen on a fluorescent screen, of diameter typically 15 cm. To ensure that the screen image is not too dim, most of the electrons that pass through the specimen should fall within this diameter, which is equivalent to a diameter of (15 cm)/M = 1.5 µm at the specimen. For viewing larger areas of specimen, however, the final-image magnification might need to be as low as 2000, requiring an illumination diameter of 75 µm at the specimen. In order to achieve the required flexibility, the condenser-lens system must contain at least two electron lenses. The first condenser (C1) lens is a strong magnetic lens, with a focal length f that may be as small as 2 mm. Using the virtual electron source(diameter ds) as its object, C1 produces areal image of diameter d1. Because the lens is located 20 cm or more below the object, the object distance, u ~ 20 cm >> f and so the image distance v ~ f. The second condenser (C2) lens is a weak magnetic lens ( f ~ several centimeters) that provides little or no magnification (M ~ 1) but allows the diameter of illumination (d) at the specimen to be varied continuously over a wide range. The C2 lens also contains the condenser aperture (the hole in the condenser diaphragm) whose diameter D can be changed in order to control the convergence semi-angle of the illumination, the maximum angle by which the incident electrons deviate from the optic axis. Figure shows lens action within the accelerating field of an electron gun, between the electron source and the anode. Curvature of the equipotential surfaces around the hole in the Wehnelt electrode constitutes a converging electrostatic lens (equivalent to a convex lens in light optics), whereas the non-uniform field just above the aperture in the anode creates a diverging lens (the equivalent of a concave lens in light optics). C. Sample Holder To allow observation in different brands or models of microscope, TEM specimens are always made circular with a diameter of 3 mm. Perpendicular to this disk, the specimen must be thin enough (at least in some regions) to allow electrons to be transmitted to form the magnified image. The specimen stage is designed to hold the specimen as stationary as possible, as any drift or vibration would be magnified in the final image, impairing its spatial resolution (especially if the image is recorded by a camera over a period of several seconds). But in order to view all possible regions of the specimen, it is also necessary to move the specimen horizontally over a distance of up to3 mm if necessary. The design of the stage must also allow the specimen to be inserted into the vacuum of the TEM column without introducing air. This is achieved by inserting the specimen through an airlock, a small chamber into which the specimen is placed initially and which can be evacuated before the specimen enters the TEM column. Not surprisingly, the specimen stage and airlock are the most mechanically complex and precision-machined parts of the TEM. There are two basic designs of the specimen stage: side-entry and top-entry. In a side-entry stage, the specimen is clamped (for example, by a threaded ring) close to the end of a rod-shaped specimen holder and is inserted horizontally through the airlock. The airlock-evacuation valve and a high-vacuum valve (at the entrance to the TEM column) are activated by rotation of the specimen holder about its long axis; see figure (a). One advantage of this side-entry design is that it is easy to arrange for precision motion of the specimen. Translation in the horizontal plane (x and y directions) and in the vertical (z) direction is often achieved by applying the appropriate movement to an end-stop that makes contact with the pointed end of the specimen holder. A further advantage of the side-entry stage is that heating of a specimen is easy to arrange, by installing a small heater at the end of the specimen holder, with electrical leads running along the inside of the holder to a power supply located outside the TEM. The ability to change the temperature of a specimen allows structural changes in a material (such as phase transitions)to be studied at the microscopic level. Specimen cooling can also be achieved, by incorporating (inside the side-entry holder) a heat-conducting metal rod whose outer end is immersed in liquid nitrogen (at 77 K). One disadvantage of the side-entry design is that mechanical vibration picked up from the TEM column or from acoustical vibrations in the external air, is transmitted directly to the specimen. In addition, any thermal expansion of the specimen holder can cause drift of the specimen and of the TEM image. These problems have been largely overcome by careful design, including choice of materials used to construct the specimen holder. As a result, side-entry holders are widely used, even for high-resolution imaging. In a top-entry stage, the specimen is clamped to the bottom end of a cylindrical holder that is equipped with a conical collar; see Figure (b). The holder is loaded into position through an airlock by means of a sliding and tilting arm, which is then detached and retracted. Inside the TEM, the cone of the specimen holder fits snugly into a conical well of the specimen stage, which can be translated in the (x and y) horizontal directions by a precision gear mechanism. The major advantage of a top-entry design is that the loading arm is disengaged after the specimen is loaded, so the specimen holder is less liable to pick up vibrations from the TEM environment. In addition, its axially symmetric design tends to ensure that any thermal expansion occurs radially about the optic axis and therefore becomes small close to the axis. However, in disadvantage views, it is more difficult to provide tilting, heating, or cooling of the specimen. Although such facilities have all been implemented in top-entry stages, they require elaborate precision engineering, making the holder fragile and expensive. Because the specimen is held at the bottom of its holder, it is difficult to collect more than a small fraction of the x-rays that are generated by the transmitted beam and emitted in the upward direction, making this design less attractive for high-sensitivity elemental analysis. D. Imaging System The sample is placed in front of the objective lens in a form of thin foil, thin section or fine particles transparent for the electron beam. (Figure. 3). The objective lens forms an image of the electron density distribution at the exit surface of the specimen based on the electron optical principles. The diffraction, projection and intermediate lenses below the objective lens are used to focus and magnify either the diffraction pattern or the image onto a fluorescent screen, which converts the electrons into visible light signal. There are three important mechanisms, which produce image contrast in the electron microscope: mass-thickness contrast, phase contrast and diffraction or amplitude contrast. i. Mass-thickness contrast arises from incoherent elastic scattering of electrons. As electrons go through the specimen they are scattered off axis by elastic nuclear interaction also called Rutherford scattering. The cross section for elastic scattering is a function of the atomic number (Z). As the thickness of the specimen increases the elastic scattering also increases since the mean-free path remains fixed. Also specimens consisting of higher Z elements will scatter more electrons than low-Z specimens. This will create differential intensity in an image formed from thicker regions where fewer electrons will be transmitted to the image compared to a thinner or low atomic number region, which will be brighter in the image plane. In TEM, the mass-thickness contrast is affected by the size of the objective aperture and the accelerating voltage. Smaller apertures will increase the difference in the ratio of scattered and transmitted electrons and as a consequence will increase the contrast between regions of different thickness of mass. Lowering the accelerating voltage will lead to similar effect since the scattering angle and the cross section increase which also will cause increase in the relative contrast between higher mass and lower mass regions. ii. Phase contrast. Some of the electrons leaving the specimen are recombined to form the image so that phase differences present at the exit surface of the specimen are converted into intensity differences in the image. Phase contrast is the dominant mechanism for object detail <10 Å and is important in lattice resolution studies and investigations of the early stages of short-range order and amorphous materials. iii. Diffraction contrast. Diffracted electrons leaving the lower surface of a crystalline specimen are intercepted by the objective aperture and prevented from contributing to the image. Alternatively only one diffracted beam forms the image. Diffraction contrast is the dominant mechanism delineating object detail >15 Å in crystalline specimens and is important and widely used contrast mechanism for study of crystal defects. Using this approach considerable quantitative information about the defect structure of the specimen may be obtained without operating the microscope at maximum resolution. Vacuum System Electron microscopes cannot operate in air for a number of reasons. The penetration of electrons through air is typically no more than 1 meter, so after coming on meter from the gun, the whole beam would be lost to collisions of the electrons with the air molecules. It is also not possible to generate the high charge difference between the anode and cathode in the gun because air is not a perfect insulator. Finally, the beam on the specimen while in air would trap all sorts of rubbish (air is full of hydrocarbon molecules) on the specimen, crack them (removing hydrogen, oxygen, etc.) and thus leave a thick carbon contamination layer on the specimen. Each electron microscope therefore has a vacuum system. The degree of sophistication of the vacuum system depends on the requirements. Simple imaging of biological thin sections is much less demanding than cryo applications or small-probe analysis in materials science and a thermionic gun can operate under much worse vacuum than a Field Emission Gun (FEG). The most basic vacuum system consists of a vessel connected to a pump that removes the air. The vacuum system of an electron microscope is considerably more complicated, containing a number of vessels, pumps, valves (to separate different vessels) and gauges (to measure vacuum pressures). From the bottom up we can distinguish four vessels in the vacuum system: The buffer tank The projection chamber The column (specimen area) The electron gun area Sometimes a tubomolecular pump (TMP), essentially a high-speed turbine fan, is used in place of (or to supplement) a diffusion pump. Usually an ion pump is used to achieve pressures below 10-4Pa, as required to operate a LaB6, Schottky, or field-emission electron source. By applying a potential difference of several kilovolts between large electrodes, a low-pressure discharge is set up (aided by the presence of a magnetic field) which removes gas molecules by burying them in one of the electrodes. Figure shows cross section through a diffusion pump. The arrows show oil vapor leaving jets within the baffle assembly. Water flowing within a coiled metal tube keeps the walls cool. Frequently, liquid nitrogen is used to help in achieving adequate vacuum inside the TEM, through a process known as cryo The Transmission Electron Microscopy Biology Essay