Molecular Biology and Evolution

Questions: 1. Would you be able to explain and portray the association among development and the legacy of hereditary material.2. You book discusses an investigation by Frederick Griffith. How did Griffiths explore alter the course of atomic science? Be explicit and completely clarify your answer. 3. Presently we should push ahead and consider the Medel tests. Talk about the association between Mendel's outcomes and the procedure of meiosis. Answer: Variety in the qualities permits a few people of a specific animal varieties to adjust as indicated by the evolving condition. The characteristic choice relies legitimately upon the phenotypes. The distinctive phenotypic variety inside a particular animal categories is caused more by hereditary varieties. Some new hereditary material can build the capacity of a life form to recreate and endure. These specific hereditary materials or alleles are conveyed to the cutting edge alongside the phenotype properties. In this way, the legacy of hereditary material empowers an animal groups to get by regardless of an unfavorable domain (Tamure et al., 2013). Frederic Griffith utilized two strains of Pneumococcus microscopic organisms, one is the pathogenic strain (III-S) and the other is the non-pathogenic strain (II-R). He infused the two strains into two mice, separately (Atzmon et on., 2010). He again infused two other mice with heat murdered pathogenic strain and a blend of warmth slaughtered pathogen and the non pathogenic strain. The mice that were infused with the pathogenic strain and the blend of warmth murdered pathogen and non pathogenic strain kicked the bucket. The other two endure. The blood of the mouse, that was infused with blend of warmth murdered pathogen and living non pathogen contained both III-S and II-R type microorganisms. Griffith inferred that by one way or another the non pathogen had changed to the pathogenic strain and he named it as The Transforming Process. This trial further prompted the different investigations of moving the hereditary materials (Tamure et al., 2013). The different hereditary tests performed by Mendel prompted the comprehension of autonomous combination of the qualities. The qualities group freely during the procedure of meiosis in an arbitrary mix in the gametes. In the meiosis procedure the two alleles of qualities gets isolated from one another and the two of them have a similar opportunity to be in a similar gamete (Atzmon et on., 2010). References: Atzmon, G., Cho, M., Cawthon, R. M., Budagov, T., Katz, M., Yang, X., ... Wright, W. E. (2010). Advancement in wellbeing and medication Sackler colloquium: Genetic variety in human telomerase is related with telomere length in Ashkenazi centenarians.Proceedings of the National Academy of Sciences of the United States of America,107, 1710-1717. Tamura, Koichiro, Glen Stecher, Daniel Peterson, Alan Filipski, and Sudhir Kumar. MEGA6: sub-atomic transformative hereditary qualities investigation adaptation 6.0.Molecular science and evolution(2013): mst197.

Individual Conflict Assessment Essay Example | Topics and Well Written Essays - 500 words

Singular Conflict Assessment - Essay Example The paper Singular Conflict Assessment discusses the social clash as a tempest utilizing individual model which is best depicted as dissimilar. On the off chance that the relational domain resembles climate, the metrological powers in the environment resemble the practices individuals take part in to address their issues and wants.Conflict in my group of birthplace is best portrayed as unique. It has been with the end goal that the meteorological powers of some have customarily consumed the assumption of others, or that the proceeded with force of certain practices has invaded the energy of others. Strife in my family has frequently been awry. By and by, I have been feeling worried about clash. I regularly feel that I am doomed in the event that I do and cursed on the off chance that I don’t. On the off chance that somebody disagrees with me and I don't avoid, they will regularly press until they see what they accept to be capitulation. On the off chance that somebody disagree s with me and I object, they will frequently blame me for being wild or rude.Likewise, I regularly felt a lot of worried about clash inside my group of starting point. I regularly felt that my voice was not heard, that I was frequently surrounded, and that for me there was no genuine equity at home. At the point when Mom and Dad were grinding away, it was natural selection between the kin present. Every so often you were more fit than others, and once in a while you just didn’t have the solidarity to retaliate. Mother and Dad once in a while agreed with me. I surmise the pressure originates from the information that occasionally nobody will be there to pay special mind to you.

Word of the Week! Arriviste Richmond Writing

Word of the Week! Arriviste Richmond Writing Last weeks parvenu provides an excellent example of a loan-word from French. English has so many of these terms that they merit their own category at the blog. Last weeks word was not quite as nasty as this also rare term, so I love it! To quote the OED, the arriviste persistently strives to advance his or her position, social status, etc., esp. to an extent considered ruthless or unscrupulous; spec. one who has recently or rapidly advanced to a social group for which he or she is considered unfit or unworthy.   We can use the term as noun or adjective. Such unwelcome and unhealthy ambition! Theres no sugar-coating our Word of the Week this time. Parvenus could, I suppose, simply want to join the crowd. Arrivistes simply do not belong. They will use any means to get in. I suppose we smile upon the parvenu who behaves well, but we should beware the arriviste. Think of the classic film  All About Eve. Things do not end well. Please send us words and metaphors useful in academic writing by e-mailing me (jessid -at- richmond -dot- edu) or leaving a comment below. See all of our Metaphors of the Month  here  and Words of the Week  here. Film image courtesy of Wikipedia Commons.

Hamlet - Misplaced Loyalty Essay examples - 878 Words

Loyalty to King and country, that is to say royalty, has historically been of paramount importance to every citizen regardless of rank or station and is exemplified in Shakespeares Hamlet. The philosophy of the divine right of kings and the natural balance of power move Hamlet into action to avenge his fathers murder and set his nation, as well has his life, back to order. He accomplishes this task though various means, though all in proportion with his end in settling with Claudius, solving differences with his mother and in sizing up his friendship with Rosencrantz and Guildenstern. Hamlet is at first understandably dismayed and mournful to hear of his fathers death but when he first learns of his fathers murder, Hamlet swears to†¦show more content†¦Hamlet furious, frantically moves to strike the King with a poisoned foil and forces him to drink of the same deadly chalice his mother did. Only in Hamlets death was he able to avenge his fathers murder by killing Claudius, but more importantly orders Horatio to record his treacherous tale so that all will know of the true King Hamlet and the imposter Claudius, Report me and my cause aright to the unsatisfied. (V, ii, 334-345). With this final act, Hamlets revenge is complete. Even before Hamlet realized his father had been murdered he bore his mother ill will for marrying, in his mind, far too soon after his fathers death. These brooding thoughts Hamlet allowed to percolate within his mind, growing stronger and stronger until he finally erupted in a fit of passionate anger when alone with his mother in act 3 when Hamlet asks her to Confess yourself to heaven, repent whats past, avoid what is to come; (III, IV, 151-152). Queen Gertrudes sins have transgressed beyond merely angering her son Hamlet, she has broken her marriage vows to her true love by marrying King Hamlets very brother, Claudius. We see Hamlets anger boil to the point at which his mother fears for her safety so that she cries out for help and it is not until the appearance of King Hamlets ghost that Hamlet remembers to Speak daggers, though use none. Sparing her life as his fathers ghost instructed him to do. Hamlet advises his mother not to sleep in such an incestuous bed andShow MoreRelate dStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesEmployers Owe Workers More Satisfying Jobs? 74 glOBalization! Culture and Work–Life Balance 76 Self-Assessment Library Am I Engaged? 78 Myth or Science? â€Å"Favorable Job Attitudes Make Organizations More Profitable† 83 Point/Counterpoint Employer–Employee Loyalty Is an Outdated Concept 87 Questions for Review 88 Experiential Exercise What Factors Are Most Important to Your Job Satisfaction? 89 Ethical Dilemma Bounty Hunters 89 Case Incident 1 Long Hours, Hundreds of E-Mails, and No Sleep: Does This SoundRead MoreDeveloping Management Skills404131 Words   |  1617 Pagesmatters not what you are thought to be, but what you are.† Alfred Lord Tennyson said: â€Å"Self-reverence, self-knowledge, self-control, these three alone lead to sovereign power.† Probably the most oft-quoted passage on the self is Polonius’ advice in Hamlet: â€Å"To thine own self be true, and it must follow as the night the day, thou canst not then be false to any man.† Messinger reminded us: â€Å"He that would govern others must ï ¬ rst master himself.† Self-awareness lies at the heart of the ability to masterRead MoreOrganisational Theory230255 Words   |  922 Pagespotential of all members of staff was more deeply embedded in managerial culture in these c ountries at an earlier period than in many other Western countries. For historical reasons, the creation of an atmosphere in which the organization can rely on loyalty and commitment is considered less risky in Nordic countries than in many others (Kreiner and Mouritsen, 2003). This democratic perspective also has its place in the United States. The development of the democratic perspective provides a link between

Alcohol and Drinking - Challenging the Legal Drinking Age...

Challenging the Legal Drinking Age Do the current laws involving the age at which adults can start drinking really make sense? There are many reasons why the government changed the legal drinking age to 21, but has this actually caused a decrease in the amount of alcohol consumed by persons between 18 and 21? Alcohol related crime and traffic accidents have gone down in recent years, but the source of this drop may not simply have to do with raising the drinking age, as the government would like you to believe. There is a theory in psychology called the Reactance Theory, which disagrees with the idea that by making more restrictive laws, drinking will slow down. The governments intent to lowering the†¦show more content†¦The proportion of underage drivers on the nations highways on Friday and Saturday nights, who tested positive for alcohol, has decreased from 10.9% in 1973, to 4.6% in 1986 and 2.8% in 1996 (Roeper Voas 755). In a study published in the American Journal of Public Health, Roeper and Voas try to focus on whether these drops on drinking and driving are due to young drivers drinking less, or by separating drinking from driving. The results of this study showed that even though drivers under the age of 21 were far less likely to drink and drive, they were also significantly more likely to have more than 6 drinks in one sitting then older drivers (Roeper Voas 756). This shows that although people drivers under 21 drink more, they still drive less. The reduction of drinking and driving probably has more to do with the zero tolerance laws, rather than having to be 21 years old to drink. The zero tolerance laws would still be a good idea even if the drinking laws were raised back to 21. As anyone who drinks alcohol somewhat regularly knows, when you first start drinking you feel it more and lose control faster. It would make sense to restrict driving even more when someone first starts drinking because of a persons low tolerance, but the age limit on when someone can first start drinking can be an independent law. Many psychologists argueShow MoreRelatedChallenging The Legal Drinking Age1689 Words   |  7 PagesMackenzie Schultz Mrs. Hamilton AP English Language 25 July 2014 Challenging the Legal Drinking Age The Minimum Legal Drinking Age (MLDA) has been challenged since the passing of the National Minimum Drinking Age Act of 1984 that raised the drinking age to twenty-one in all fifty states (Ogilvie). Advocates for lowering the MLDA to eighteen years of age argue that this change will eliminate the thrill of breaking the law for young adults entering college and boost the national economy. SupportersRead MoreThe Debate Over A Proper Legal Drinking Age1243 Words   |  5 Pagesover a proper legal drinking age has been ongoing for decades. Some people believe twenty-one is the right age for legally consuming alcohol, while others believe twenty-one is too old. There are many supporters of an age limit of eighteen on alcohol consumption, but it has not been enough to sway Congress away from their set age of twenty-one. One major advocate for the age of twenty-one is the organization MADD, or â€Å"Mothers Against Drunk Driving†. This organization supports the age of twenty-oneRea d MoreTeen Alcoholism Is Driven By Example1150 Words   |  5 Pagessees someone else drinking, for whatever reason, and they imitate them to either save he or she’s pride and be â€Å"cool† or use is as e remedy to try to feel better about a situation they are in or to numb an unpleasant emotion they do not know how to deal with. affects the physical state of a young person, but also one’s current situations and relationships, and the outcome of he or she’s futures. â€Å"People who begin drinking before age 15 are four times more likely to develop alcohol dependence at someRead MoreThe Problem Of Driving Under The United States1332 Words   |  6 PagesWhen an individual consumes a drink, the alcohol is directed to the blood stream, there are tests that measure how much alcohol is in the system with an approximation percentage. Having 8% percent of alcohol in your body is already considered over board and the person is guessed to be a danger to society if driving a vehicle. DUI is considered to be the nations most committed crime up to date, back in the 80’s people started supporting ways to fight drinking and driving, and were willing to give upRead MorePros And Cons Of Lowering The Drinking Age1822 Words   |  8 PagesAlthough not always the case, the legal drinking age in the United States is 21 years old. However, the minimum legal drinking age drastically varies across the rest of the globe, with some countries allowing legal al cohol consumption before individuals have even turned 18 years old. Since the legal drinking age was changed to 21 years, it has been a controversial issue in the United States. For decades, there have been debates on the pros and cons of lowering the legal age. In fact, there have even beenRead MoreEssay on Drunk Driving as a Social Issue1693 Words   |  7 Pagesbut unsafe to operate an automobile if you are under the influence of alcohol. When a person drinks, the alcohol is absorbed into the blood stream and various tests have been designed to measure the level of alcohol in a person’s blood. In most states, if a person has a blood alcohol level greater than .10%, that person is presumed to be too intoxicated to safely operate an automobile. Driving under the influence of alcohol is considered the nation’s most frequently committed violent crime, andRead MoreHow The Cage Can Be Treated For Adults And Adolescents Over The Age Of 16 ( Aertgeerts )874 Words   |  4 Pagesalcohol in the morning to elude withdrawal and to steady their nerves (Aertgeerts, et al., 2004). These transitional questions, in spite of missing discriminative value, are beneficial for familiarizing the subject, as well as making the consultation less threatening (Aertgeerts, et al., 2004). Item responses are scored zero to one, with a higher score a suggestion of alcohol problems. The total score can range from zero to four (Aertg eerts, et al., 2004). This screening apparatusRead MoreKeeping A Diary Doubles Diet Weight Loss980 Words   |  4 PagesThe Experiment on Alcohol effect on Opposite Sex Attractiveness The independent variable in the experiment was alcohol intake. This variable was manipulated by having the control group drink flavored water and by having the experimental group drink the actual alcohol drink. The dependent variable was level of attractiveness, which was affected by alcohol intake. The level of attractiveness depended on drink served (alcoholic or nonalcoholic). The conclusion that alcohol makes people ofRead MoreThe Diagnosis Of Addiction Clients1576 Words   |  7 PagesGolden Age: 38 Date of Examination: August 18, 2015 Ethnicity: Caucasian Gender: Male Presenting Problem: Mr. Thomas is a married 38 year old Caucasian suffering from Alcohol Use Disorder. Although married, he and his wife constantly argues about his drinking, and she has even stopped sleeping with him when he drinks. He was recently arrested for drinking and driving (DUI/DWI), and was advised by his attorney to quit drinking andRead MoreChildhood Alcoholism And The Effect Of The 12 Step Program For Alcoholics Anonymous As A Form Of Treatment1147 Words   |  5 Pagesdoes, result in illnesses and deaths. â€Å"Alcohol is the world’s third largest risk factor for disease and contributes to 4 [percent] of the global burden of disease† (Marshall, 2014). In relation to alcoholism, specifically adolescent alcoholism is a growing concern in the United States. The age at which young people are starting to experiment with alcohol is younger than ever. Dr. Don Macdonald explains that this may most likely be due to the fact that it is legal for the majority of th e population.

Buddhism The Foundation, Development and Beliefs Free Essays

Though the other divisions of Buddhism have altered their practices to accommodate the needs of a wider range of people, Theravada has remained virtually the same as it was at its founding. Theravada Buddhism is the original and most popular form of Buddhism in Sri Lanka, Thailand, Laos, Cambodia, and Myanmar. Theravada remains closest to the original teachings of the founder of Buddhism, Siddhartha Gautama. We will write a custom essay sample on Buddhism: The Foundation, Development and Beliefs or any similar topic only for you Order Now Siddhartha Gautama is the original founder of all forms of Buddhism. He was born in present day Nepal around 563 B. C. E. He was a prince of the Shakyas clan, and likely heir to his father’s throne. He was named â€Å"Siddhartha† which means â€Å"he who has attained his goals. † Being the prince of the warrior caste, he trained in the arts of war and grew up to be a strong and handsome young man. When he was at the age of sixteen, he fought and defeated his competitors in a variety of sports, which won him the hand of the beautiful princess Yashodhara, who was also sixteen years old at the time. He continued living in the luxury of his palaces. Soon, however, he grew restless and began to wonder what happens outside the palace. He eventually insisted to be permitted to come out of the palace so he can see his people and his lands. For fear of the prince leading a religious life, the king ordered that only young and healthy people should greet the prince so that he will not see the kind of suffering. However, even with the king’s careful orders, he still caught sight of a couple of old men, who accidentally wandered near the parade route, at Kapilavatthu, the capital. Curious of who these people were, he chased after them. He then came to a place where some people are desperately ill and even came across a funeral ceremony by the side of the river, seeing death for the first time in his life. Siddhartha saw four sights: a sick man, a poor man, a beggar, and a corpse. When he caught sight of these, his heart soon filled with vast loneliness for the suffering that humanity has to go through. He then asked his friend and squire Chandaka what those things meant. Chandaka told him that all of us grow old, sick and eventually, die, saying that these truths should have been told to him before. (Boeree, 1999). He said upon seeing these realities: â€Å"When ignorant people see someone who is old, they are disgusted and horrified, even though they too will be old some day. I thought to myself: I don’t want to be like the ignorant people. After that, I couldn’t feel the usual intoxication with youth anymore. When ignorant people see someone who is sick, they are disgusted and horrified, even though they too will be sick some day. I thought to myself: I don’t want to be like the ignorant people. After that, I couldn’t feel the usual intoxication with health anymore. When ignorant people see someone who is dead, they are disgusted and horrified, even though they too will be dead some day. I thought to myself: I don’t want to be like the ignorant people. After than, I couldn’t feel the usual intoxication with life anymore. † (AN III. 39, interpreted) (Boeree, 1999) He also saw an ascetic or a monk who has abandoned all the pleasures and cravings of the flesh. What struck Siddhartha the most is the peaceful expression on the monk’s face, which left a deep impression on him. Going back to the palace after this and despite having what appeared to be the perfect life of luxury, Siddhartha became very discontent with the material world and decided to leave his family. He realized that he could no longer live happy with the thought that, even with all their luxury, there would still come a time that he will suffer and die. With these thoughts, he soon wondered what he may do so that he can overcome suffering, more than anything else. He left his privileged life as a prince and ran away to the forest in search of spiritual understanding. For a while, he studied with two well-known gurus of that time but soon found that their practice is not enough to answer his question. That was when he began to follow the practices of a group of five ascetics: austerities and self-mortifications. For six years, he practiced with utmost sincerity and intensity that the five ascetics became his followers before long. However, he still did not find the answers he was looking for. He decided to double his efforts by refusing food and water until he was in a state of near death. One day, Sujata, a peasant girl saw this starving monk. She took pity on him and offered him to eat some of her milk-rice. Soon, he realized that self-mortification still do not help him answer his questions. He decided to carry out a practice that will be middle way between the extremes of luxurious and self-mortification life. For many days, Siddhartha sat beneath a particular fig tree, called the bodhi tree, in the town of Bodh Gaya, vowing that he will never stand up until he found the answers to the problem of suffering. At first, he deeply concentrated in clearing his mind from all distractions, and later on, in mindless meditation. They said that he started to recall all his previous lives, and see everything that was going on in the entire universe. He became the Buddha, meaning â€Å"he who is awake†, with the rising of the morning star on the full moon of May, when he finally found the answers he was looking for (Hooker, 1996). He spent the next forty five years teaching others about the path to enlightenment. After an exhaustive ministry he died around 483 B. C. E. During his life, none of Siddhartha Gautama’s teachings were ever written down. During the following 100 years after his death, Buddhism spread throughout India and Sri Lanka. A group of Buddhist monks held a council in the Capital city of Patna, during the third century B. C. E. , to come to a consensus on what the original teachings of Siddhartha were. When the council came to agreement about Siddhartha’s true original teachings, the teachings became the doctrine of Theravada Buddhism. Theravada Buddhism has not deviated from this doctrine since. Theravada Buddhism’s main goal is for the individual practitioner to reach Nirvana. This is accomplished by realizing the very foundation of Buddhism which was the â€Å"Four Noble Truths†: The Four Noble Truths: 1. ) All human life is suffering (dhukka ). 2. ) All suffering is caused by human desire, particularly the desire that impermanent things be permanent. 3. ) Human suffering can be ended by ending human desire. 4. ) Desire can be ended by following the â€Å"Eightfold Noble Path†: right understanding, right thought, right speech, right action, right livelihood, right effort, right mindfulness, and right concentration (Bullitt, 2005). The practitioner must also follow the Eight Fold Path; 1. ) right view, 2. ) right resolve, 3. ) right speech, 4. ) right action, 5. ) right livelihood, 6. ) right effort, 7. ) right mindfulness, and 8. ) right concentration. The council all also agreed in practicing the â€Å"Four Cardinal virtues† which were friendliness, compassion, joy, and equanimity. During the onset of Buddhism, the religion comprised of only very few followers making it relatively insignificant among the vast variety of Hindu sects. But when Asoka, the great Mauryan emperor converted to Buddhism in the third century BC, the young and insignificant religion soon spread profusely throughout India and was carried across the Indian Ocean to Sri Lanka. Just like rumors change as they are spread from person to person, Buddhism was slightly altered over time. The original form Theravada Buddhism, held its ground in Sri Lanka as the Buddhists of Sri Lanka maintained a form that was most similar to the original form of Siddhartha’s teachings. On the other hand, the rest of India, then the world in general later on, Buddhism fragmented into a million sects and versions. Theravada Buddhism requires intensive meditation. To follow his form of Buddhism requires the practitioner to devote a lifetime to its practice, thus making it difficult or even imposable for the average modern person to commit to such an undertaking. Despite the extreme demands of Theravada Buddhism, it is gaining popularity in Singapore, Australia as well as other parts of the western world. There are over 100 million Theravada Buddhists worldwide. Theravada has had less success spreading than other forms of Buddhism. Forms of Buddhism such as Zen are much more user friendly and are less demanding. Theravada Buddhism might not be the most popular, but it remains true to teachings of the genius who founded the religion. Just as well, Buddhism is in fact, a way of life. References: Boeree, D. C. G. (1999). The Life of Siddhartha Gautama. Retrieved February 21, 2007, from http://webspace. ship. edu/cgboer/siddhartha. html Bullitt, J. (2005). What is Theravada Buddhism? Hooker, R. (1996). The Historical Siddhartha [Electronic Version]. Retrieved February 21, 2007 from http://www. wsu. edu/~dee/BUDDHISM/SIDD. HTM. How to cite Buddhism: The Foundation, Development and Beliefs, Papers

Welding Process free essay sample

Energy beam welding methods, namely laser beam welding and electron beam welding, are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser-hybrid welding, which uses principles from both laser beam welding and arc welding for even better weld properties. Electron Beam Welding Introduction: Electron Beam Welding (EEW) is a unique way of delivering large amounts of concentrated thermal energy to materials being welded. We will write a custom essay sample on Welding Process or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page It became viable as a production process in the late 1950s. At that time, it was used mainly in the aerospace and nuclear industries. Since then, it has become the welding technique with the widest range of applications. This has resulted from the ability to use the very high energy density of the beam to weld parts ranging in sizes from very delicate small components using just a few watts of power to welding steel at a thickness of 10 to 12 inches with 100 Kilowatts or more. However, even today most of the applications are less than 1/2 in thickness, and cover a wide variety of metals and even dissimilar metal joints How it works: The most common Electron Beam systems used in manufacturing today are of the high vacuum design. The other machine types are: 1- Partial vacuum equipment. 2- Non-vacuum equipment. These two types are used in mass production where high output is important. The diagram shown shows the classic triode gun and column assembly. The triode gun design consists of the cathode (Filament), Bias cup (Grid) and Anode. Other sub-assembly components that contribute to the triode are: High voltage insulator Feed-through, high voltage cable and deflection coils. All these components are housed in a vacuum vessel called the upper column. The column assembly is held under a high vacuum by an isolation valve positioned below the anode assembly. The vacuum environment provides several benefits: †¢Removes the bulk gas molecules necessary for a stable triode. †¢Provides protection for the incandescent filament against oxidization. †¢Provides a controlled environment to protect the gun against welding by product. BeamFormation:UpperColumn The beam formatting begins with the emission of electrons from the incandescently heated tungsten filament. During this process the filament is saturated by a determined amount of the electrical current. Electrons boil off the filament tip as it reaches operating temperatures and gathers in the grid cup assembly. A negative high voltage potential (acceleration voltage) is applied to the filament cathode assembly with the cathode assembly charged at 150 kV the only force preventing the electron beam from propagating is a secondary negatively charged voltage that resides on the grid cup or bias assembly. This voltage respectively lower than the accelerating voltage acts as a valve that controls the volume of electron energy that can flow from the cathode emitter to its attracting target. The anode at a positive potential is one of the attracting targets in the triode but its role is more of a beam formation device rather than a collector of electrons. The secondary target is the work piece which is usually metallic and offers a conductive path to earth to complete the circuit. The electron gun assembly design is a result of some extensive engineering studies and experimentation. Some of the early triode designs were mathematically modeled and their designs still produced today. Beam Delivery: Lower Column Other important components of the beam delivery column are the focus and deflection coils and isolation valve. The magnetic focus coil located beneath the anode assembly provides the means for squeezing the beam into a tightly focused stream of energy or can be used to widely dispersed energy resource. The deflection coil is another important component that will contribute to the latter discussion of beam control parameters but for now we will simply say that it is a steering device. The focus coil is circular in design and is concentric with the column. An electrical current is passed through the coil which produces the resultant magnetic fluxes that act to converge the electron beam. The deflection coil is configured with four separately wound coils positioned at right angles to the column. The four coils are segmented as sets (x and y) each axis becomes a separate control allowing the energizing of each axis on command, thus steering the beam. Many industrial applications require the precise manipulation of the beam energy so as to provide a pattern for processing. This is usually accomplished by superimposing an AC signal onto the four coils simultaneously therefore creating a specific pattern. The isolation valve serves to isolate the vacuum environment in the upper column from the lower. After the electron beam has passed through the lower column, it enters the chamber cavity. Another important part of the lower column of the (EBW) machine is the viewing optics, the optics are arranged in the lower column in such a manner that when viewing the beam energy through a video camera or magnified optics it gives the view from a parallel plane, giving the viewer the perception of looking down the column. Beam Interaction in Chamber Cavity: As the beam enters the chamber cavity it is aimed onto a target material placed at a determined height representative of the actual work piece. This procedure is typical in most pre-weld set-up requirements. The welding technician would then follow a process of beam alignment and beam parameter calibration. Unlike laser, the preparation is quite different in the fact that the technician must view the actual beam through the optical system in order to verify the beam alignment and focus. With a laser beam, the technician could not view the beam quality and therefore must rely on instrumentation to profile the beam energy. Once the beam has been tuned and calibrated the equipment is now ready for part processing. The focused beam of electrons is impinged at a targeted location on the weld joint at which point the kinetic energy of the electrons is converted to thermal energy. The work piece can either be stationary and the beam energy deflected or the work piece can be traversed along a desired axis of motion. This motion can be computer controlled such as a CNC table or simply a rotating mechanism can be employed. As the beam energy is applied to the moving part several physical transformations take place. The material instantly begins to melt at the surface and a rapid vaporization occurs followed by the resultant coalescence. Two welding modes are used in the (EBW): 1) Conductance mode: Mainly applicable to thin materials, heating of the weld joint to melting temperature is quickly generated at below the materials surface followed by thermal conductance throughout the joint for complete or partial penetration. The resulting weld is very narrow for two reasons: a) It is produced by a focused beam spot with energy densities concentrated into a . 010 to. 030 area. b) The high energy density allows for quick travel speeds allowing the weld to occur so fast that the adjacent base metal does not absorb the excess heat therefore giving the E. B. process its distinct minimal heat affected zone. 2) Keyhole mode: It is employed when deep penetration is a requirement. This is possible since the concentrated energy and velocity of the electrons of the focused beam are capable of subsurface penetration. The subsurface penetration causes the rapid vaporization of the material thus causing a hole to be drilled through the material. In the whole cavity the rapid vaporization and sputtering causes a pressure to develop thereby suspending the liquidus material against the cavity walls. As the hole is advanced along the weld joint by motion of the work piece the molten layer flows around the beam energy to fill the hole and coalesce to produce a fusion weld. The hole and trailing solidifying metal resemble the shape of an old fashion keyhole. Both the conductance and keyhole welding modes share physical features such as narrow welds and minimal heat affected zone . The basic difference is that a keyhole weld is a full penetration weld and a conductance weld usually carries a molten puddle and penetrates by virtue of conduction of thermal energy. Advantages: 1. Deeper and narrower: Ability to achieve a high depth-to-width ratio eliminating multiple-pass welds. 2. Low heat input: Minimal shrinkage and distortion as well as ability to weld in close proximity to heat sensitive components. 3. Superior strength: Vacuum melt quality can yield 95% strength of base material. 4. Versatility: From . 001 to 3 deep penetration welds, each performed with exceptional control and repeatability. 5. High purity: Vacuum environment eliminates impurities such as oxides and nitrides. 6. Superior process: Permits welding of refractory metals and combinations of many dissimilar metals not easily weld with conventional welding processes. Disadvantages 1. All metals which can be welded by arc processes can be also welded by Electron-Beam-Welding, including exotic ones. Equipment tends to be expensive though, but there are joints which cannot be economically welded by any other process. Finally Electron-Beam-Welding is successfully applied for repair, overhaul and maintenance of expensive items, because it has almost no influence on nearby material. . On the sides of disadvantages of Electron-Beam-Welding one must include the elevated cost of equipment, the relatively high pump-down time, the need for properly designed joints, special fixtures and expert personnel. Laser Beam Welding Introduction: Laser Beam Welding (LBW) is a modern welding process; it is a high energy beam process that continues to expand into modern industries and new applications because of its many advantages like deep weld penetration and minimizing heat inputs. The turn by the manufacturers to automate the welding processes has also caused to the expansion in using high technology like the use of laser and computers to improve the product quality through more accurate control of welding processes. Major Difference: The main difference between traditional electric arc welding processes is in the mode of energy transfer. Unlike electric arc energy transfer, laser energy absorption by a material is affected by many factors like the type of the laser, incident power density and the base metal’s surface condition. Two important factors to help characterizing laser welding are: ) The energy transfer efficiency, -The ratio of the heat observed by the work piece to the incident laser energy. b) The melting efficiency -The ratio of the heat to just melt the fusion zone to the heat observed by the work piece. The laser output is not electrical because does not require electrical continuity. It is also not influenced by magnetism and not limite d to electrically conductive materials. It can contract with any material and its function doesn’t require a vacuum nor does it produce x-rays. How it works: The focal spot is targeted on the work piece surface which will be welded. At the surface the large concentration of light energy is converted into thermal energy. The surface of the work piece starts melting and progresses through it by surface conductance. For welding, the beam energy is maintained below the vaporization temperature of the work piece material because hole drilling or cutting vaporization is required because the penetration of the work piece depends on conducted heat. The thickness of the materials to be welded is generally less than 0. 80 inches if the ideal metallurgical and physical characteristics of laser welding must be realized. Concentrated energy produces melting and coalescence before a heat affected zone is developed. When the materials to be welded are thick and have high thermal conductivity like aluminum. The advantage of having a minimal heat affected zone can be seriously affected because the heat source in this type of welding process is the energy of light, the work piece will be welded purely which means the fatigue strength of the welded joint will be excellent. Energy distribution across the beam is generated by the design of the resonant cavity, including mirror curvatures or shape and their relative arrangement. This combination results in photon oscillation within the cavity specific output beam energy patterns, these patterns are called Transverse Energy Modes (TEMs). The function of all laser beam welding processes whether they be gas (carbon dioxide, helium, neo, etc. ) or other lasing sources is based on the principles of the excitation of atoms using intense light, electricity, electron beams, chemicals and etc. The role of focusing lenses in this process is really important because it concentrates the beam energy into a focal spot as small as 0. 005 in diameters or even less. Like mentioned above there are many types of Laser Beam Welding (LBW) but the most popular types in the industry are: 1. Nd:YAG (neodymium-yttrium aluminum garnet) Laser: The Nd: YAG laser uses a man-made crystal as its active medium and produces light with a 1. 06-micron wavelength. 2. Carbon Dioxide Lasers: The CO2 laser uses a mixture of gases including CO2 as the active medium and produces light with a 10. 6-micron wavelength. 3. The Diode Laser: The diode laser uses a semi-conductor diode material as its active medium can be manufactured to produce one of several wavelengths. Industries Served: 1- Aerospace. 2- Defense/military. 3- Electronics. 4- Research development. 5- Medical. 6- Sensors instrumentation. 7- Petrochemical refining. 8- Communications energy. Advantages: 1) Deep and narrow welds can be done. 2) Absence of distortion in welds created. 3) Minimal heat affected zones in welds created. 4) Excellent metallurgical quality will be established in welds. 5) Ability to weld smaller, thinner components. 6) Increased travel speeds. 7) Non-contact welding. Laser-hybrid Welding It is a new type of welding process that combines the principles of laser eam welding and arc welding. Introduction: The combination of laser light and arc into an amalgamated welding process is known since the 1970’s, but for a long time thereafter no further research and development was undertaken. Recently, researchers have turned their attention to this topic again and attempted to unite the advantages of the arc with those of the laser in a hybrid weld process. W hereas in the early days, laser sources still had to prove their suitability for industrial use, nowadays they are standard technological equipment in many manufacturing enterprises. The combination of laser welding with another weld process is called â€Å"hybrid welding process†. This means that a laser beam and an arc act simultaneously in one welding zone, they influence and support each other. Laser: Laser welding not only requires high laser power but also a high quality beam to obtain the desired â€Å"deep-weld effect†. The resulting higher quality of beam can be exploited either to obtain a smaller focus diameter or a larger focal distance. For the projects that are currently underway, a lamp-pumped solid state laser with a laser beam power of 4 kW is used. The laser light is transmitted via a 600? m glass fibre, in which the beginning and the end is water-cooled. The laser beam is projected onto the work piece by a focusing module with a focal distance of 200 mm. Laser Hybrid process: For welding metallic work pieces, the Nd:YAG laser beam is focused to obtain intensities of more than 106W/cm2. When the laser beam hits the surface of the material, this spot is heated up to vaporization temperature, and a vapor cavity is formed in the weld metal due to the escaping metal vapor. The extraordinary feature of the weld seam is its high depth-to-width ratio. The energy-flow density of the freely burning arc is slightly more than 104 W/cm2. Unlike a sequential configuration where two separate weld processes act in succession, hybrid welding may be viewed as a combination of both weld processes acting simultaneously in one and the same process zone. Depending on the kind of arc or laser process used, and depending on the process parameters, the processes will influence each other to a different extent and in different ways. The combination of the laser process and the arc process, there is also an increase in both weld penetration depth and welding speed (as compared to each single process). The metal vapor escaping from the vapor cavity acts upon the arc plasma. Absorption of the Nd:YAG laser radiation in the processing plasma remains negligible. Depending on the ratio of the two power inputs, the character of the overall process may be mainly determined either by the laser or by the arc. Absorption of the laser radiation is substantially influenced by the temperature of the work piece surface. Before the laser welding process can start, the initial reflectance must be overcome, especially on aluminum surfaces. This can be achieved by starting welding with a special start program. After the vaporization temperature has been reached, the vapor cavity is formed, and nearly all radiation energy can be put into the work piece. The energy required for this is thus determined by the temperature dependent absorption and by the amount of energy lost by conduction into the rest of the work piece. In Laser Hybrid welding, vaporization takes place not only from the surface of the work piece but also from the filler wire, so that more metal vapor is available, which in turn facilitates the input of the laser radiation. Advantages Laser hybrid process provides a fast welding speed and large gap capability. Other benefits include the penetration properties of laser welding and the addition of consumables and bridge-building properties of MIG. The use of consumables in the hybrid method means that the metallurgy of the joint can be influenced. This makes the method suitable for use with high-strength steels, with which consumables are needed to get the required properties out of the joint. Duplex stainless steel, employed widely by the offshore industry, can only be welded with a consumable, making it suitable with the hybrid method, but not with conventional laser welding. Conclusion The arc welding processes are cheap and reliable, but in light of the demands from modern society certain important limitations have become crucial. Many properties such as speed, heat input, and environmental aspects may not be improved further due to the limitations caused by the physics of the processes and the distortions observed in arc welding. Of equal importance are the large difficulties met in robotizing the processes where control of the individual weld-pass geometry is a key issue. Substituting with energy beam welding results in many advantages such as low distortion, high speed, and natural automation. Especially introduction of laser/MAG (GMAW) hybrid welding instead of pure laser welding increases the ability to bridge a gap and provides a significant increase in speed when welding a wide gap, and excellent weld properties are obtained. Thus, energy beam welding has bring a lot of advantages to mankind especially in manufacturing sector which then catalyst the progression of economic of one country.