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Posted: January 14, 2017 at 9:04 pm
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GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester, , (CAS Number) 157115-85-0, (PubChem) CID 180496, C17H22N2O4
Among the studies cited, the effective doses ranged from .01mg/kg to 10 mg/kg (in rats and mice); when subjected to allometric scaling, this range would be equivalent to .002mg/kg to 2.445 mg/kg in humans [7,10,13]. In a 70kg (154lbs) adult human, the dosing range would be 171mcg to 171mg.
Typically, the most cited dosing range (anecdotally) is 10-30mg, up to 3 times per day, usually dosed sublingually or orally.
Patented in 1995, Noopept is a Nootropic substance that is a dipeptide similar in effect to Piracetam ; it is often cited as being 1000 times more potent (by weight) than Piracetam. Noopept has high oral bioavailability, and appears to potentiate its own effects with chronic administration. Noopept has shown promise in treating many different aspects of cognitive decline that warrants more research, especially in human models.
Noopept has been noted to have four main mechanisms of action; the first noted mechanism of action is antioxidation: in vitro studies of Noopept have shown signs that it operates on an antioxidative mechanism of action which protects neurons from apoptosis . The second noted mechanism of action of Noopept is inhibition of glutamate neurotoxicity ; glutamate neurotoxicity leads to quick cell death, and is linked to a variety of neurological disorders such as autism and Alzheimers disease. The third mechanism of action of Noopept is increased neuronal plasticity , which can lead to greater adaptability in learning and memory. The fourth mechanism of action that has been noted in Noopept is increases expression of phenylacetic acid, prolyglycine, and cyclo-prolyglycine in the brain , which are endogenous Nootropics.
What makes Noopept an intriguing nootropic is its myriad of positive effects, lack of noted negative side effects, and its effectiveness in both chronic and acute usage. In both in vivo and in vitro models, Noopept was shown to have positive effects on all stages of memory, from learning to recall, as well as anxiolytic effects . An in vitro study showed Noopept to be neuroprotective against the use of H2O2 in neuronal degradation, in both healthy brains as well as those with Downs Syndrome in a dose-dependent manner . In rat models of memory impairment, Noopept was shown to improve memory retention and retrieval, and improve learning which was shown through the use of passive avoidance response testing . Rats with ischemic lesions were treated with Noopept for nine days and then tested with the passive avoidance test; those rats that had been treated performed significantly better than the control group; Noopept was also shown to be neuroprotective through antioxidation in the rats who received treatment for nine days . Studies also showed that rats given a single oral administration of Noopept showed improved scores on the passive avoidance test . Another study showed that rats who had gone through olfactory bulbectomies showed Alzheimers like symptoms, but after 21 days of dosing Noopept, spatial memory improved greatly which was evidenced through the use of the Morris Water Maze test .
Two other interesting benefits of Noopept were noted; one dealing with BDNF and NGF, and the other dealing with the immune system. One study showed rats treated with Noopept, both chronically and acutely, were found to have a higher expression of mRNA BDNF and NGF; even more interestingly, after 28 days of treatment no tolerance towards Noopept was detected and there was some evidence the effects of Noopept potentiate the longer it is administered . Another study looked at the effect of Noopept on immune deficient mice; the researchers found Noopept to have immuno-corrective properties .
Among the studies cited, doses up to 10mg/kg in rats have shown no toxicity, which when subjected to allometric scaling yields a dose of 2.445mg/kg in humans (or 171 mg for a 70kg person); in fact, Noopept has been shown to be neuroprotective at said dosage [7,10,13].
Support SmarterNootropics by purchasing from this product from one of our recommended suppliers:
USA and Worldwide: Absorb Health (Powder & Capsules) | Pure Nootropics (Powder & Capsules) | Nootropics Depot (Powder| Capsules)
European Union and United Kingdom: Intellimeds ( Powder|Capsules|10mg Tablets|20mg Tablets)
Ostrovskaia RU, Gudasheva TA, Voronina TA, Seredenin SB. The original novel nootropic and neuroprotective agent noopept. Eksp Klin Farmakol. 2002 Sep-Oct;65(5):66-72. 
Neznamov GG, Teleshova ES. Comparative studies of Noopept and piracetam in the treatment of patients with mild cognitive disorders in organic brain diseases of vascular and traumatic origin. Neuroscience and Behavioral Physiology Volume 39, Issue 3 , pp 311-321. 
SEREDENIN SERGEI B, VORONINA TATIANA A, GUDASHEVA TATIANA A, OSTROVSKAYA RITA U,
ROZANTSEV GRIGORI G, SKOLDINOV ALEXANDER P, TROPHIMOV SERGEI S, HALIKAS JAMES A, GARIBOVA TAISIJA L. Biologically active n-acylprolydipeptides having antiamnestic, antihypoxic and anorexigenic effects. US5439930 (A) 1995-08-08. 
Alejandra P, Hoyo-Vadillo C, Gudasheva T, Serednin S, Ostrovskaya R, Busciglio J. GVS-111 prevents oxidative damage and apoptosis in normal and Downs Syndrome human cortical neurons. International Journal of Developmental Neuroscience, Vol 21 Issue 3 May 2003 Pages 117-124. 
Kovalenko, Shipaeva, Alekseeva, Pronin, Durnev, Gudasheva, Ostrovskaja, Seredenin. Immunopharmacological properties of noopept. Bulletin of Experimental Biology and Medicine Volume 144, Issue 1 , pp 49-52. 
G. A. Romanova, F. M. Shakova, T. A. Gudasheva, R. U. Ostrovskaya. Impairment of Learning and Memory after Photothrombosis of the Prefrontal Cortex in Rat Brain: Effects of Noopept. Bulletin of Experimental Biology and Medicine Volume 134, Issue 6 , pp 528-530. 
Ostrovskaya R, Romanova G, Barskov I, Shanina E, Gudasheva T, Victorov I, Voronina T, Seredenin S. Memory restoring and neuroprotective effects of the proline-containing dipeptide, GVS-111, in a photochemical stroke model. Behavioural Pharmacology: September 1999. 
R. U. Ostrovskaya, T. A. Gudasheva, A. P. Zaplina, Ju. V. Vahitova, M. H. Salimgareeva, R. S. Jamidanov, S. B. Seredenin. Noopept stimulates the expression of NGF and BDNF in rat hippocampus. Bulletin of Experimental Biology and Medicine Volume 146, Issue 3 , pp 334-337. 
S. S. Boiko, R. U. Ostrovskaya, V. P. Zherdev, S. A. Korotkov, T. A. Gudasheva, T. A. Voronina, S. B. Seredenin. Pharmacokinetics of new nootropic acylprolyldipeptide and its penetration across the blood-brain barrier after oral administration. Bulletin of Experimental Biology and Medicine Volume 129, Issue 4 , pp 359-361. 
R. U. Ostrovskaya, T. Kh. Mirsoev, G. A. Romanova, T. A. Gudasheva, E. V. Kravchenko, C. C. Trofimov, T. A. Voronina, S. B. Seredenin. Proline-Containing Dipeptide GVS-111 Retains Nootropic Activity after Oral Administration. Bulletin of Experimental Biology and Medicine Volume 132, Issue 4 , pp 959-962. 
Solntseva E, Bukanova J, Ostrovskaya R, Gudasheva T, Voronina T, Skrebitsky V. The effects of piracetam and its novel dipeptide analogue GVS-111 on neuronal voltage-gated calcium and potassium channels. General Pharmacology: The Vascular System, Volume 29 Issue 1, July 1997. 
T. A. Gudasheva, S. S. Boyko, R. U. Ostrovskaya, T. A. Voronina, V. K. Akparov, S. S. Trofimov, G. G. Rozantsev, A. P. Skoldinov, V. P. Zherdev, S. B. Seredenin. The major metabolite of dipeptide piracetam analogue GVS-111 in rat brain and its similarity to endogenous neuropeptide cyclol-prolylglycine. European Journal of Drug Metabolism and Pharmacokinetics Volume 22, Issue 3 , pp 245-252. 
Ostrovskaya RU, Gruden MA, Bobkova NA, Sewell RD, Gudasheva TA, Samokhin AN, Seredinin SB, Noppe W, Sherstnev VV, Morozova-Roche LA. The nootropic and neuroprotective prolinecontaining dipeptide noopept restores spatial memory and increases immunoreactivity to amyloid in an Alzheimers disease model. J Psychopharmacol August 2007 vol. 21 no. 6 611-61
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Posted: January 12, 2017 at 1:48 pm
matt: I just listened to the loftus-dsouza debate and as a consequence left the william lane craig should debate john loftus group at facebook. I dont know what others here think, but I have never heard such terrible debating (loftus). dinesh dsouza is the most overrated and small-minded debater in the english speaking universe, as far as im concerned. his arguments are like cardboard cutout versions of anything william craig has to say, for one thing because he makes no effort to hide his cultural and ideological bigotry. (he actually claims with a straight face that christians invented empathy as a moral good. what an asshole.) loftus comes across as a well-meaning college student trying to argue with his professor. i dont understand why theres a movement to see him embarrass himself and atheism generally by publically confronting the Terminator of christian apologetics himself. soooo disappointing!
As entirely disappointing as it is to say this, I am in complete agreement with Matt. I am unwilling, after listening to this, to cast my name in the vote for Loftus to debate Mr. Craig. Naively, I was hoping, especially after becoming aware of the fervent almost zealous nature of Loftus pursuit of Craig, that this would not only be the introduction of a worthy gun-slinging atheist debate protagonist but that if this epic showdown took place, it would have the added poetry of it being the student who is finally able to best the theistic Samurai. Like I said; Naive.
Typically, I dont criticize without visiting some of the reasons for my criticism.
1) There are several themes Loftus runs with in this debate, they continually come up ineffectively and provide nothing of real substance. He opens up with one; essentially telling everyone that Dinesh is just brainwashed. Which, although true, isnt something that couldnt be slung right back at him as we all know theists to do as they believe we dont believe because we dont want culpability moral or otherwise, so therefore, weve brainwashed ourselves into disbelief. Fortunately, Dinesh doesnt pick up this thread and engage Loftus in playing a sort of merry-go-round styled No, youre the brainwashed one.. No, you are.. No, YOU are…
2) Another theme is his constant return to Well all the sects of these religions critique each other and theyre all right, effectively eliminating religion in front of our very eyes. This is repeated quite frequently in this debate and Im sure Ill have more to say about it later.
3) I was inconceivably shocked with his statement History is all in the mind. He quickly tried to cover his tracks by following that up with something like well, thats what some philosophers of history say, anyway. His reasoning, as it could be inferred from what he said just prior to this utterance, was basically that history writers can only write from their perspective so given what may be of that perspective, they may have rationale for remaining skeptical of something that actually happened. Yikes.
4)Generally, about his opening remarks, he is just all over the place. There is no introduction of his arguments he just shifts left and talks about Quantum fluctuation rendering the singularity at the inception of our universe not likely therefore removing the beginning of the universe theory out of the Christians favor then all of a sudden he shifts right and now were talking about Jesus not delivering his scriptural message well and thereby is responsible for all the religious wars in his name then if there is God, hes to blame for the tsunamis. Loftus, the opening statement is the only time you have to not scramble about trying to address all of your antagonists remarks. You should have complete lucidity at this point in the game. Perhaps collecting your thoughts at the outset and introducing your arguments with more clarity of mind, e.g.
Ok, our first batter up on the atheist lineup is going to be the evidential argument from evil, it goes like this: 1) If there is an omniscient, omnipotent, all-loving God..
Our next argument is a quick rejoinder to the First Cause argument, which is something like this: 1) Everything that begins to exist..
Instead of touching briefly on all of them, narrow your selection down to a few and expound on them in greater detail leaving Dinesh to either spend a huge chunk of his time rebutting you or, should he chose not to, being able in your first rebuttal to say Hey, remember that huge argument of the problem of evil looks like Dinesh agrees with me as he apparently has no reply.
5) Loftus, at a few points in the debate calls Dinesh something which must have been new to his huge ears: Charming. Dinesh Dsouza is not charming. He is an arrogant, unsophisticated, misleading to the point of purposefully deceiving bucket of fuck. He is good at appearing to have a legit reply to atheistic arguments which are so transparently fraught with specious reasoning and argumentative fallacies that they render him ineligible to be charming.
6) Ive actually taken the trouble to transcribe the next part because I didnt think people would believe me when I said I bet I could find the worst conceivable argument for the atheistic creation-scenario. This was in response to, and was in fact introduced as such by Loftus himself as, Now, Dinesh has asked me to give an account of the creation of the universe.
even though Im not a scientist, what I do know, is that scientists all agree that there was no cosmic singularity. Now I cant do the math. Uhh, I can not do Victor Stengers math. He has done the math. Uhh, ::clears throat:: But, he says, given the laws of nature, its a 60% chance that something should have happened, something should be there, something should exist. 60%. Given the laws of nature.
Yep. Word for word. You can hear this enlightening account of our origins at the 41:28 point. Prepare to be underwhelmed.
7) Loftus closing, opens with this gem: I guess things got heated a little bit.. but, uh, its you know, it doesnt have to be but it does. Illuminating. Loftus then spends more then his first minute of his five minute closing telling everyone that the real way to learn is from the books. I must say, I would feel a bit slapped in the face as someone who Ive paid to listen to tell me I should pay, instead, to read him. Im not saying hes wrong. You can certainly learn more from a 300 page dissection of theism then what collectively amounts to 35 or 40 minutes worth of lectures, but to use that time so inefficiently is irritating. How about using that time to effectively rebut one of Dineshs arguments? Or constructing one of your own against Christianity? A task youve been flown in and paid to do. He then spends the rest of his closing telling everyone they should just be agnostic because theyre agnostic/atheistic towards every other religion so basically, just be consistent. Have you read any other religions? No? Then you should just discard yours too. we deny scientology, we deny mormons, we deny muslims Im sorry, maybe Im being unfairly critical but who the hell has ever been converted after being told that line? Who, after being made to realize that they havent given fair intellectual treatment to greek mythology, has right then and there renounced Christ for good?
Loftus and Dsouza were very generous and permitted almost another hour of questioning following there closings.
Before I submit this rather harsh review of Loftus debating skills, I have to say, as I believe Ive stated before, Why I Became An Atheist was one of the best, most helpful books I read in the atheistic/agnostic/naturalist cannon of probably 20-30 books Ive read in the past 2 or 3 years. I enjoyed it thoroughly. Notes for future thoughts and arguments poured out of me while reading that book and I recommend and cite it in my own writing quite often. So maybe my resentment is as a result of placing so much FAITH in Mr Loftus as an author that I unfairly expected too much of him as a neophyte debater.
I do, with the utmost sincerity hope, that if you are reading this Mr Loftus (as I know you frequent this site) you take some note of how this looks to your fellow nonbelievers. Were relying on you, as one of the few out there headlining debates on our behalf. You know the crowd of people at your back are of an intellectual breed and as such, we demand the highest caliber arguments be offered in our defense. You clearly display a great deal of passion for these topics and Im hoping I can count on that to have you take better care to prepare your thoughts in the future. As well as to focus your arguments and speak with more clarity and precision. Look at your former mentor. He doesnt race through his speeches. He has a calm, very collected vibe and hardly repeats the same thing in a single debate whereas, a lot of what you said, you said in almost the same wording in multiple places (i.e. the religion cancels each other out argument).
Posted: at 1:41 pm
What is the Mormon Transhumanist Association?
The Mormon Transhumanist Association is the worlds largest advocacy network for ethical use of technology and religion to expand human abilities, as outlined in the Transhumanist Declaration and the Mormon Transhumanist Affirmation. Although we are neither a religious organization nor affiliated with any religious organization, we support our members in their personal religious affiliations, Mormon or otherwise, and encourage them to adapt Transhumanism to their unique situations.
Increasingly, persons are recognizing parallels and complements between Mormon and Transhumanist views. On the one hand, Mormonism is a religion of the Judeo-Christian tradition that advocates immersive discipleship of Jesus Christ that leads to creative and compassionate works. On the other hand, Transhumanism is a mostly secular ideology that advocates ethical use of technology to expand human abilities. However, Mormonism and Transhumanism advocate remarkably similar views of human nature and potential: material beings organized according to natural laws, rapidly advancing knowledge and power, imminent fundamental changes to anatomy and environment, and eventual transcendence of present limitations. Resources available through this site provide details on the relation between Mormon and Transhumanist views.
Transfigurism is religious Transhumanism, exemplified by syncretization of Mormonism and Transhumanism. The term transfigurism denotes advocacy for change in form, and alludes to sacred stories from many religious traditions, such as the Universal Form of Krishna in Hinduism, the Radiant Face of Moses in Judaism, the Wakening of Gautama Buddha in Buddhism, the Transfiguration of Jesus Christ in Christianity, and the Translation of the Three Nephites in Mormonism. Transfigurism also alludes to prophecies, such as the Rapture in Christianity and the Day of Transfiguration in Mormonism.
The 14 founding members of the Mormon Transhumanist Association began organizing on 3 March 2006 and adopted a constitution on 13 May 2006. We incorporated in Utah of the United States on 4 August 2006, and received 501c3 nonprofit status in the United States, effective the same date. We affiliated with Humanity+ (formerly the World Transhumanist Association) on 6 July 2006 and renewed our affiliation on 2 October 2010.
As of September 2015, the Mormon Transhumanist Association consisted of 549 members, with approximately 24% living in Utah and 65% living in the United States. According to a survey in 2014, 62% of our members were also members of The Church of Jesus Christ of Latter-day Saints (the largest Mormon denomination) and 59% identified as theists. On social politics, 53% identified as progressive, 20% as conservative, and 18% as moderate. On economic politics, 32% identified as moderate, 32% as progressive, and 29% as conservative. All members of the association support the Transhumanist Declaration and the Mormon Transhumanist Affirmation.
The association requires that all members support the Transhumanist Declaration and the Mormon Transhumanist Affirmation. Support does not entail a specific interpretation or perfect agreement with these statements. A person may be a member of the association in good standing while sincerely holding to an interpretation of the statements that differs from that of another member, or while not fully agreeing or even constructively disagreeing with parts of these statements, so long as that person supports the Declaration and Affirmation on the whole. For example, the gospel of Jesus Christ is defined in the Affirmation as to trust in, change toward, and fully immerse our bodies and minds in the role of Christ, to become compassionate creators. Support for this statement may not require belief in or specific beliefs about the existence of God. Interpretation of the Declaration and Affirmation is ultimately the responsibility of each member. The association does not sanction a specific interpretation, and it does not expect perfect agreement.
The Mormon Transhumanist Association shares media, news, and opinions about the intersection of Mormonism with science and technology and Transhumanism with religion and spirituality. We engage as a community in discussions and conferences about prophetic vision, scientific discovery, technological innovation, as well as opportunities and risks in our rapidly changing world. We also act with common purpose on team projects to cure disease, and extend and enhance life.
Help the Mormon Transhumanist Association promote radical flourishing in compassion and creation through technology and religion. Join the association and engage in online or offline discussions. Link your website to ours. Start a blog on religion, science, spirituality or technology, and tell us about it. Attend a conference. Participate in a team project. Donate to the cause. Thank you!
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About | Mormon Transhumanist Association
Posted: January 11, 2017 at 1:56 pm
What AreAlternative Medicine Graduate Programs?
Alternative Medicine graduate programs are ideal for students who are interested in healthcare that is not part of
If you are considering degrees in alternative medicine, its a good idea to determine what area of this broad field you wish to focus on. Some alternative medicine schools may offer programs in acupuncture, naturopathy, Chinese medicine, osteopathic medicine, and more. Take the time to learn about each of these concentrations to find out what interests you.
Also consider degree level. Current medical practitioners may want to consider a graduate certificate that could enhance their knowledge of a particular area of alternative medicine. If you are entering this field for the first time, you might consider a Masters Degree in Alternative Medicine or a Doctorate Program in Alternative Medicine from accredited naturopathic schools or alternative medicine colleges. Or you can search online alternative medicine programs.Finally, decide whether you want to pursue a traditional degree, take your courses online, or give hybrid learning a try. The choice is yours!
See the article here:
Posted: January 10, 2017 at 2:53 am
In recent years, a rise in verbal abuse and violence directed at people of color, lesbians and gay men, and other historically persecuted groups has plagued the United States. Among the settings of these expressions of intolerance are college and university campuses, where bias incidents have occurred sporadically since the mid-1980s. Outrage, indignation and demands for change have greeted such incidents — understandably, given the lack of racial and social diversity among students, faculty and administrators on most campuses.
Many universities, under pressure to respond to the concerns of those who are the objects of hate, have adopted codes or policies prohibiting speech that offends any group based on race, gender, ethnicity, religion or sexual orientation.
That’s the wrong response, well-meaning or not. The First Amendment to the United States Constitution protects speech no matter how offensive its content. Speech codes adopted by government-financed state colleges and universities amount to government censorship, in violation of the Constitution. And the ACLU believes that all campuses should adhere to First Amendment principles because academic freedom is a bedrock of education in a free society.
How much we value the right of free speech is put to its severest test when the speaker is someone we disagree with most. Speech that deeply offends our morality or is hostile to our way of life warrants the same constitutional protection as other speech because the right of free speech is indivisible: When one of us is denied this right, all of us are denied. Since its founding in 1920, the ACLU has fought for the free expression of all ideas, popular or unpopular. That’s the constitutional mandate.
Where racist, sexist and homophobic speech is concerned, the ACLU believes that more speech — not less — is the best revenge. This is particularly true at universities, whose mission is to facilitate learning through open debate and study, and to enlighten. Speech codes are not the way to go on campuses, where all views are entitled to be heard, explored, supported or refuted. Besides, when hate is out in the open, people can see the problem. Then they can organize effectively to counter bad attitudes, possibly change them, and forge solidarity against the forces of intolerance.
College administrators may find speech codes attractive as a quick fix, but as one critic put it: “Verbal purity is not social change.” Codes that punish bigoted speech treat only the symptom: The problem itself is bigotry. The ACLU believes that instead of opting for gestures that only appear to cure the disease, universities have to do the hard work of recruitment to increase faculty and student diversity; counseling to raise awareness about bigotry and its history, and changing curricula to institutionalize more inclusive approaches to all subject matter.
A: Free speech rights are indivisible. Restricting the speech of one group or individual jeopardizes everyone’s rights because the same laws or regulations used to silence bigots can be used to silence you. Conversely, laws that defend free speech for bigots can be used to defend the rights of civil rights workers, anti-war protesters, lesbian and gay activists and others fighting for justice. For example, in the 1949 case of Terminiello v. Chicago, the ACLU successfully defended an ex-Catholic priest who had delivered a racist and anti-semitic speech. The precedent set in that case became the basis for the ACLU’s successful defense of civil rights demonstrators in the 1960s and ’70s.
The indivisibility principle was also illustrated in the case of Neo-Nazis whose right to march in Skokie, Illinois in 1979 was successfully defended by the ACLU. At the time, then ACLU Executive Director Aryeh Neier, whose relatives died in Hitler’s concentration camps during World War II, commented: “Keeping a few Nazis off the streets of Skokie will serve Jews poorly if it means that the freedoms to speak, publish or assemble any place in the United States are thereby weakened.”
A: Not so. Only a handful of the several thousand cases litigated by the national ACLU and its affiliates every year involves offensive speech. Most of the litigation, advocacy and public education work we do preserves or advances the constitutional rights of ordinary people. But it’s important to understand that the fraction of our work that does involve people who’ve engaged in bigoted and hurtful speech is very important:
Defending First Amendment rights for the enemies of civil liberties and civil rights means defending it for you and me.
A: The U.S. Supreme Court did rule in 1942, in a case calledChaplinsky v. New Hampshire, that intimidating speech directed at a specific individual in a face-to-face confrontation amounts to “fighting words,” and that the person engaging in such speech can be punished if “by their very utterance [the words] inflict injury or tend to incite an immediate breach of the peace.” Say, a white student stops a black student on campus and utters a racial slur. In that one-on-one confrontation, which could easily come to blows, the offending student could be disciplined under the “fighting words” doctrine for racial harassment.
Over the past 50 years, however, the Court hasn’t found the “fighting words” doctrine applicable in any of the hate speech cases that have come before it, since the incidents involved didn’t meet the narrow criteria stated above. Ignoring that history, the folks who advocate campus speech codes try to stretch the doctrine’s application to fit words or symbols that cause discomfort, offense or emotional pain.
A: Symbols of hate are constitutionally protected if they’re worn or displayed before a general audience in a public place — say, in a march or at a rally in a public park. But the First Amendment doesn’t protect the use of nonverbal symbols to encroach upon, or desecrate, private property, such as burning a cross on someone’s lawn or spray-painting a swastika on the wall of a synagogue or dorm.
In its 1992 decision inR.A.V. v. St. Paul, the Supreme Court struck down as unconstitutional a city ordinance that prohibited cross-burnings based on their symbolism, which the ordinance said makes many people feel “anger, alarm or resentment.” Instead of prosecuting the cross-burner for the content of his act, the city government could have rightfully tried him under criminal trespass and/or harassment laws.
The Supreme Court has ruled that symbolic expression, whether swastikas, burning crosses or, for that matter, peace signs, is protected by the First Amendment because it’s “closely akin to ‘pure speech.'” That phrase comes from a landmark 1969 decision in which the Court held that public school students could wear black armbands in school to protest the Vietnam War. And in another landmark ruling, in 1989, the Court upheld the right of an individual to burn the American flag in public as a symbolic expression of disagreement with government policies.
A: Historically, defamation laws or codes have proven ineffective at best and counter-productive at worst. For one thing, depending on how they’re interpreted and enforced, they can actually work against the interests of the people they were ostensibly created to protect. Why? Because the ultimate power to decide what speech is offensive and to whom rests with the authorities — the government or a college administration — not with those who are the alleged victims of hate speech.
In Great Britain, for example, a Racial Relations Act was adopted in 1965 to outlaw racist defamation. But throughout its existence, the Act has largely been used to persecute activists of color, trade unionists and anti-nuclear protesters, while the racists — often white members of Parliament — have gone unpunished.
Similarly, under a speech code in effect at the University of Michigan for 18 months, white students in 20 cases charged black students with offensive speech. One of the cases resulted in the punishment of a black student for using the term “white trash” in conversation with a white student. The code was struck down as unconstitutional in 1989 and, to date, the ACLU has brought successful legal challenges against speech codes at the Universities of Connecticut, Michigan and Wisconsin.
These examples demonstrate that speech codes don’t really serve the interests of persecuted groups. The First Amendment does. As one African American educator observed: “I have always felt as a minority person that we have to protect the rights of all because if we infringe on the rights of any persons, we’ll be next.”
A: Bigoted speech is symptomatic of a huge problem in our country; it is not the problem itself. Everybody, when they come to college, brings with them the values, biases and assumptions they learned while growing up in society, so it’s unrealistic to think that punishing speech is going to rid campuses of the attitudes that gave rise to the speech in the first place. Banning bigoted speech won’t end bigotry, even if it might chill some of the crudest expressions. The mindset that produced the speech lives on and may even reassert itself in more virulent forms.
Speech codes, by simply deterring students from saying out loud what they will continue to think in private, merely drive biases underground where they can’t be addressed. In 1990, when Brown University expelled a student for shouting racist epithets one night on the campus, the institution accomplished nothing in the way of exposing the bankruptcy of racist ideas.
A: Yes. The ACLU believes that hate speech stops being just speech and becomes conduct when it targets a particular individual, and when it forms a pattern of behavior that interferes with a student’s ability to exercise his or her right to participate fully in the life of the university.
The ACLU isn’t opposed to regulations that penalize acts of violence, harassment or intimidation, and invasions of privacy. On the contrary, we believe that kind of conduct should be punished. Furthermore, the ACLU recognizes that the mere presence of speech as one element in an act of violence, harassment, intimidation or privacy invasion doesn’t immunize that act from punishment. For example, threatening, bias-inspired phone calls to a student’s dorm room, or white students shouting racist epithets at a woman of color as they follow her across campus — these are clearly punishable acts.
Several universities have initiated policies that both support free speech and counter discriminatory conduct. Arizona State, for example, formed a “Campus Environment Team” that acts as an education, information and referral service. The team of specially trained faculty, students and administrators works to foster an environment in which discriminatory harassment is less likely to occur, while also safeguarding academic freedom and freedom of speech.
A: The ACLU believes that the best way to combat hate speech on campus is through an educational approach that includes counter-speech, workshops on bigotry and its role in American and world history, and real — not superficial — institutional change.
Universities are obligated to create an environment that fosters tolerance and mutual respect among members of the campus community, an environment in which all students can exercise their right to participate fully in campus life without being discriminated against. Campus administrators on the highest level should, therefore,
ACLU Executive Director Ira Glasser stated, in a speech at the City College of New York: “There is no clash between the constitutional right of free speech and equality. Both are crucial to society. Universities ought to stop restricting speech and start teaching.”
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Hate Speech on Campus | American Civil Liberties Union
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An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld game consoles and PDAs. A major area of research is the development of white OLED devices for use in solid-state lighting applications.
There are two main families of OLED: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix (AMOLED) addressing schemes. Passive matrix OLEDs (PMOLED) uses a simple control scheme in which you control each row (or line) in the display sequentially whereas active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes.
An OLED display works without a backlight; thus, it can display deep black levels and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions (such as a dark room), an OLED screen can achieve a higher contrast ratio than an LCD, regardless of whether the LCD uses cold cathode fluorescent lamps or an LED backlight.
Andr Bernanose and co-workers at the Nancy-Universit in France made the first observations of electroluminescence in organic materials in the early 1950s. They applied high alternating voltages in air to materials such as acridine orange, either deposited on or dissolved in cellulose or cellophane thin films. The proposed mechanism was either direct excitation of the dye molecules or excitation of electrons.
In 1960 Martin Pope and some of his co-workers at New York University developed ohmic dark-injecting electrode contacts to organic crystals. They further described the necessary energetic requirements (work functions) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices. Pope’s group also first observed direct current (DC) electroluminescence under vacuum on a single pure crystal of anthracene and on anthracene crystals doped with tetracene in 1963 using a small area silver electrode at 400 volts. The proposed mechanism was field-accelerated electron excitation of molecular fluorescence.
Pope’s group reported in 1965 that in the absence of an external electric field, the electroluminescence in anthracene crystals is caused by the recombination of a thermalized electron and hole, and that the conducting level of anthracene is higher in energy than the exciton energy level. Also in 1965, W. Helfrich and W. G. Schneider of the National Research Council in Canada produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes, the forerunner of modern double-injection devices. In the same year, Dow Chemical researchers patented a method of preparing electroluminescent cells using high-voltage (5001500 V) AC-driven (1003000Hz) electrically insulated one millimetre thin layers of a melted phosphor consisting of ground anthracene powder, tetracene, and graphite powder. Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules.
Roger Partridge made the first observation of electroluminescence from polymer films at the National Physical Laboratory in the United Kingdom. The device consisted of a film of poly(N-vinylcarbazole) up to 2.2 micrometers thick located between two charge injecting electrodes. The results of the project were patented in 1975 and published in 1983.
Hong Kong-born American physical chemist Ching W. Tang and his co-worker Steven Van Slyke at Eastman Kodak built the first practical OLED device in 1987. This was a revolution for the technology. This device used a novel two-layer structure with separate hole transporting and electron transporting layers such that recombination and light emission occurred in the middle of the organic layer; this resulted in a reduction in operating voltage and improvements in efficiency.
Research into polymer electroluminescence culminated in 1990 with J. H. Burroughes et al. at the Cavendish Laboratory in Cambridge reporting a high efficiency green light-emitting polymer based device using 100nm thick films of poly(p-phenylene vinylene).
Universal Display Corporation holds the majority of patents concerning the commercialization of OLEDs.
A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a substrate. The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over part or all of the molecule. These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors.
Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes et al., which involved a single layer of poly(p-phenylene vinylene). However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing a more gradual electronic profile, or block a charge from reaching the opposite electrode and being wasted. Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer. More recent developments in OLED architecture improves quantum efficiency (up to 19%) by using a graded heterojunction. In the graded heterojunction architecture, the composition of hole and electron-transport materials varies continuously within the emissive layer with a dopant emitter. The graded heterojunction architecture combines the benefits of both conventional architectures by improving charge injection while simultaneously balancing charge transport within the emissive region.
During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the quality of their optical transparency, electrical conductivity, and chemical stability. A current of electrons flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton, a bound state of the electron and hole. This happens closer to the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region. The frequency of this radiation depends on the band gap of the material, in this case the difference in energy between the HOMO and LUMO.
As electrons and holes are fermions with half integer spin, an exciton may either be in a singlet state or a triplet state depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light-emitting diodes make use of spinorbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency.
Indium tin oxide (ITO) is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the HOMO level of the organic layer. A typical conductive layer may consist of PEDOT:PSS as the HOMO level of this material generally lies between the workfunction of ITO and the HOMO of other commonly used polymers, reducing the energy barriers for hole injection. Metals such as barium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the LUMO of the organic layer. Such metals are reactive, so they require a capping layer of aluminium to avoid degradation.
Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface adhesion, increase electrical resistance, and allow for more frequent formation of non-emissive dark spots in the OLED material adversely affecting lifetime. Mechanisms to decrease anode roughness for ITO/glass substrates include the use of thin films and self-assembled monolayers. Also, alternative substrates and anode materials are being considered to increase OLED performance and lifetime. Possible examples include single crystal sapphire substrates treated with gold (Au) film anodes yielding lower work functions, operating voltages, electrical resistance values, and increasing lifetime of OLEDs.
Single carrier devices are typically used to study the kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through the device is composed of only one type of charge carrier, either electrons or holes, recombination does not occur and no light is emitted. For example, electron only devices can be obtained by replacing ITO with a lower work function metal which increases the energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection.
Efficient OLEDs using small molecules were first developed by Dr. Ching W. Tang et al. at Eastman Kodak. The term OLED traditionally refers specifically to this type of device, though the term SM-OLED is also in use.
Molecules commonly used in OLEDs include organometallic chelates (for example Alq3, used in the organic light-emitting device reported by Tang et al.), fluorescent and phosphorescent dyes and conjugated dendrimers. A number of materials are used for their charge transport properties, for example triphenylamine and derivatives are commonly used as materials for hole transport layers. Fluorescent dyes can be chosen to obtain light emission at different wavelengths, and compounds such as perylene, rubrene and quinacridone derivatives are often used. Alq3 has been used as a green emitter, electron transport material and as a host for yellow and red emitting dyes.
The production of small molecule devices and displays usually involves thermal evaporation in a vacuum. This makes the production process more expensive and of limited use for large-area devices, than other processing techniques. However, contrary to polymer-based devices, the vacuum deposition process enables the formation of well controlled, homogeneous films, and the construction of very complex multi-layer structures. This high flexibility in layer design, enabling distinct charge transport and charge blocking layers to be formed, is the main reason for the high efficiencies of the small molecule OLEDs.
Coherent emission from a laser dye-doped tandem SM-OLED device, excited in the pulsed regime, has been demonstrated. The emission is nearly diffraction limited with a spectral width similar to that of broadband dye lasers.
Researchers report luminescence from a single polymer molecule, representing the smallest possible organic light-emitting diode (OLED) device. Scientists will be able to optimize substances to produce more powerful light emissions. Finally, this work is a first step towards making molecule-sized components that combine electronic and optical properties. Similar components could form the basis of a molecular computer.
Polymer light-emitting diodes (PLED), also light-emitting polymers (LEP), involve an electroluminescent conductive polymer that emits light when connected to an external voltage. They are used as a thin film for full-spectrum colour displays. Polymer OLEDs are quite efficient and require a relatively small amount of power for the amount of light produced.
Vacuum deposition is not a suitable method for forming thin films of polymers. However, polymers can be processed in solution, and spin coating is a common method of depositing thin polymer films. This method is more suited to forming large-area films than thermal evaporation. No vacuum is required, and the emissive materials can also be applied on the substrate by a technique derived from commercial inkjet printing. However, as the application of subsequent layers tends to dissolve those already present, formation of multilayer structures is difficult with these methods. The metal cathode may still need to be deposited by thermal evaporation in vacuum. An alternative method to vacuum deposition is to deposit a Langmuir-Blodgett film.
Typical polymers used in pleaded displays include derivatives of poly(p-phenylene vinylene) and polyfluorene. Substitution of side chains onto the polymer backbone may determine the colour of emitted light or the stability and solubility of the polymer for performance and ease of processing.
While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVs and related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or water have been prepared via ring opening metathesis polymerization. These water-soluble polymers or conjugated poly electrolytes (CPEs) also can be used as hole injection layers alone or in combination with nanoparticles like graphene.
Phosphorescent organic light emitting diodes use the principle of electrophosphorescence to convert electrical energy in an OLED into light in a highly efficient manner, with the internal quantum efficiencies of such devices approaching 100%.
Typically, a polymer such as poly(N-vinylcarbazole) is used as a host material to which an organometallic complex is added as a dopant. Iridium complexes such as Ir(mppy)3 are currently the focus of research, although complexes based on other heavy metals such as platinum have also been used.
The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling, facilitating intersystem crossing between singlet and triplet states. By using these phosphorescent materials, both singlet and triplet excitons will be able to decay radiatively, hence improving the internal quantum efficiency of the device compared to a standard pleaded where only the singlet states will contribute to emission of light.
Applications of OLEDs in solid state lighting require the achievement of high brightness with good CIE coordinates (for white emission). The use of macromolecular species like polyhedral oligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species such as Ir for printed OLEDs have exhibited brightnesses as high as 10,000cd/m2.
Patternable organic light-emitting devices use a light or heat activated electroactive layer. A latent material (PEDOT-TMA) is included in this layer that, upon activation, becomes highly efficient as a hole injection layer. Using this process, light-emitting devices with arbitrary patterns can be prepared.
Colour patterning can be accomplished by means of laser, such as radiation-induced sublimation transfer (RIST).
Organic vapour jet printing (OVJP) uses an inert carrier gas, such as argon or nitrogen, to transport evaporated organic molecules (as in organic vapour phase deposition). The gas is expelled through a micrometre-sized nozzle or nozzle array close to the substrate as it is being translated. This allows printing arbitrary multilayer patterns without the use of solvents.
Conventional OLED displays are formed by vapor thermal evaporation (VTE) and are patterned by shadow-mask. A mechanical mask has openings allowing the vapor to pass only on the desired location.
Like ink jet material depositioning, inkjet etching (IJE) deposits precise amounts of solvent onto a substrate designed to selectively dissolve the substrate material and induce a structure or pattern. Inkjet etching of polymer layers in OLED’s can be used to increase the overall out-coupling efficiency. In OLEDs, light produced from the emissive layers of the OLED is partially transmitted out of the device and partially trapped inside the device by total internal reflection (TIR). This trapped light is wave-guided along the interior of the device until it reaches an edge where it is dissipated by either absorption or emission. Inkjet etching can be used to selectively alter the polymeric layers of OLED structures to decrease overall TIR and increase out-coupling efficiency of the OLED. Compared to a non-etched polymer layer, the structured polymer layer in the OLED structure from the IJE process helps to decrease the TIR of the OLED device. IJE solvents are commonly organic instead of water based due to their non-acidic nature and ability to effectively dissolve materials at temperatures under the boiling point of water.
For a high resolution display like a TV, a TFT backplane is necessary to drive the pixels correctly. Currently, low temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) is used for commercial AMOLED displays. LTPS-TFT has variation of the performance in a display, so various compensation circuits have been reported. Due to the size limitation of the excimer laser used for LTPS, the AMOLED size was limited. To cope with the hurdle related to the panel size, amorphous-silicon/microcrystalline-silicon backplanes have been reported with large display prototype demonstrations.
Transfer-printing is an emerging technology to assemble large numbers of parallel OLED and AMOLED devices efficiently. It takes advantage of standard metal deposition, photolithography, and etching to create alignment marks commonly on glass or other device substrates. Thin polymer adhesive layers are applied to enhance resistance to particles and surface defects. Microscale ICs are transfer-printed onto the adhesive surface and then baked to fully cure adhesive layers. An additional photosensitive polymer layer is applied to the substrate to account for the topography caused by the printed ICs, reintroducing a flat surface. Photolithography and etching removes some polymer layers to uncover conductive pads on the ICs. Afterwards, the anode layer is applied to the device backplane to form bottom electrode. OLED layers are applied to the anode layer with conventional vapor deposition, and covered with a conductive metal electrode layer. As of 2011[update] transfer-printing was capable to print onto target substrates up to 500mm X 400mm. This size limit needs to expand for transfer-printing to become a common process for the fabrication of large OLED/AMOLED displays.
The different manufacturing process of OLEDs lends itself to several advantages over flat panel displays made with LCD technology.
OLED technology is used in commercial applications such as displays for mobile phones and portable digital media players, car radios and digital cameras among others. Such portable applications favor the high light output of OLEDs for readability in sunlight and their low power drain. Portable displays are also used intermittently, so the lower lifespan of organic displays is less of an issue. Prototypes have been made of flexible and rollable displays which use OLEDs’ unique characteristics. Applications in flexible signs and lighting are also being developed.Philips Lighting have made OLED lighting samples under the brand name “Lumiblade” available online and Novaled AG based in Dresden, Germany, introduced a line of OLED desk lamps called “Victory” in September, 2011.
OLEDs have been used in most Motorola and Samsung color cell phones, as well as some HTC, LG and Sony Ericsson models.Nokia has also introduced some OLED products including the N85 and the N86 8MP, both of which feature an AMOLED display. OLED technology can also be found in digital media players such as the Creative ZEN V, the iriver clix, the Zune HD and the Sony Walkman X Series.
The Google and HTC Nexus One smartphone includes an AMOLED screen, as does HTC’s own Desire and Legend phones. However, due to supply shortages of the Samsung-produced displays, certain HTC models will use Sony’s SLCD displays in the future, while the Google and Samsung Nexus S smartphone will use “Super Clear LCD” instead in some countries.
OLED displays were used in watches made by Fossil (JR-9465) and Diesel (DZ-7086).
Other manufacturers of OLED panels include Anwell Technologies Limited (Hong Kong),AU Optronics (Taiwan),Chimei Innolux Corporation (Taiwan),LG (Korea), and others.
In 2009, Shearwater Research introduced the Predator as the first color OLED diving computer available with a user replaceable battery.
DuPont stated in a press release in May 2010 that they can produce a 50-inch OLED TV in two minutes with a new printing technology. If this can be scaled up in terms of manufacturing, then the total cost of OLED TVs would be greatly reduced. DuPont also states that OLED TVs made with this less expensive technology can last up to 15 years if left on for a normal eight-hour day.
The use of OLEDs may be subject to patents held by Universal Display Corporation, Eastman Kodak, DuPont, General Electric, Royal Philips Electronics, numerous universities and others. There are by now thousands of patents associated with OLEDs, both from larger corporations and smaller technology companies.
RIM, the maker of BlackBerry smartphones, uses OLED displays in their BlackBerry 10 devices.
A technical writer at the Sydney Herald thinks foldable OLED smartphones could be as much as a decade away because of the cost of producing them. There is a relatively high failure rate when producing these screens. As little as a speck of dust can ruin a screen during production. Creating a battery that can be folded is another hurdle. However, Samsung has accelerated its plans to release a foldable display by the end of 2015
Textiles incorporating OLEDs are an innovation in the fashion world and pose for a way to integrate lighting to bring inert objects to a whole new level of fashion. The hope is to combine the comfort and low cost properties of textile with the OLEDs properties of illumination and low energy consumption. Although this scenario of illuminated clothing is highly plausible, challenges are still a road block. Some issues include: the lifetime of the OLED, rigidness of flexible foil substrates, and the lack of research in making more fabric like photonic textiles.
By 2004 Samsung, South Korea’s largest conglomerate, was the world’s largest OLED manufacturer, producing 40% of the OLED displays made in the world, and as of 2010 has a 98% share of the global AMOLED market. The company is leading the world of OLED industry, generating $100.2 million out of the total $475 million revenues in the global OLED market in 2006. As of 2006, it held more than 600 American patents and more than 2800 international patents, making it the largest owner of AMOLED technology patents.
Samsung SDI announced in 2005 the world’s largest OLED TV at the time, at 21 inches (53cm). This OLED featured the highest resolution at the time, of 6.22 million pixels. In addition, the company adopted active matrix based technology for its low power consumption and high-resolution qualities. This was exceeded in January 2008, when Samsung showcased the world’s largest and thinnest OLED TV at the time, at 31inches (78cm) and 4.3mm.
In May 2008, Samsung unveiled an ultra-thin 12.1inch (30cm) laptop OLED display concept, with a 1,280768 resolution with infinite contrast ratio. According to Woo Jong Lee, Vice President of the Mobile Display Marketing Team at Samsung SDI, the company expected OLED displays to be used in notebook PCs as soon as 2010.
In October 2008, Samsung showcased the world’s thinnest OLED display, also the first to be “flappable” and bendable. It measures just 0.05mm (thinner than paper), yet a Samsung staff member said that it is “technically possible to make the panel thinner”. To achieve this thickness, Samsung etched an OLED panel that uses a normal glass substrate. The drive circuit was formed by low-temperature polysilicon TFTs. Also, low-molecular organic EL materials were employed. The pixel count of the display is 480 272. The contrast ratio is 100,000:1, and the luminance is 200cd/m2. The colour reproduction range is 100% of the NTSC standard.
In the same month, Samsung unveiled what was then the world’s largest OLED Television at 40-inch with a Full HD resolution of 1920 1080 pixels. In the FPD International, Samsung stated that its 40-inch OLED Panel is the largest size currently possible. The panel has a contrast ratio of 1,000,000:1, a colour gamut of 107% NTSC, and a luminance of 200cd/m2 (peak luminance of 600cd/m2).
At the Consumer Electronics Show (CES) in January 2010, Samsung demonstrated a laptop computer with a large, transparent OLED display featuring up to 40% transparency and an animated OLED display in a photo ID card.
Samsung’s latest AMOLED smartphones use their Super AMOLED trademark, with the Samsung Wave S8500 and Samsung i9000 Galaxy S being launched in June 2010. In January 2011 Samsung announced their Super AMOLED Plus displays, which offer several advances over the older Super AMOLED displays: real stripe matrix (50% more sub pixels), thinner form factor, brighter image and an 18% reduction in energy consumption.
At CES 2012, Samsung introduced the first 55″ TV screen that uses Super OLED technology.
On January 8, 2013, at CES Samsung unveiled a unique curved 4K Ultra S9 OLED television, which they state provides an “IMAX-like experience” for viewers.
On August 13, 2013, Samsung announced availability of a 55-inch curved OLED TV (model KN55S9C) in the US at a price point of $8999.99.
On September 6, 2013, Samsung launched its 55-inch curved OLED TV (model KE55S9C) in the United Kingdom with John Lewis.
Samsung introduced the Galaxy Round smartphone in the Korean market in October 2013. The device features a 1080p screen, measuring 5.7 inches (14cm), that curves on the vertical axis in a rounded case. The corporation has promoted the following advantages: A new feature called “Round Interaction” that allows users to look at information by tilting the handset on a flat surface with the screen off, and the feel of one continuous transition when the user switches between home screens.
The Sony CLI PEG-VZ90 was released in 2004, being the first PDA to feature an OLED screen. Other Sony products to feature OLED screens include the MZ-RH1 portable minidisc recorder, released in 2006 and the Walkman X Series.
At the 2007 Las Vegas Consumer Electronics Show (CES), Sony showcased 11-inch (28cm, resolution 960540) and 27-inch (68.5cm), full HD resolution at 1920 1080 OLED TV models. Both claimed 1,000,000:1 contrast ratios and total thicknesses (including bezels) of 5mm. In April 2007, Sony announced it would manufacture 1000 11-inch (28cm) OLED TVs per month for market testing purposes. On October 1, 2007, Sony announced that the 11-inch (28cm) model, now called the XEL-1, would be released commercially; the XEL-1 was first released in Japan in December 2007.
In May 2007, Sony publicly unveiled a video of a 2.5-inch flexible OLED screen which is only 0.3 millimeters thick. At the Display 2008 exhibition, Sony demonstrated a 0.2mm thick 3.5inch (9cm) display with a resolution of 320200 pixels and a 0.3mm thick 11inch (28cm) display with 960540 pixels resolution, one-tenth the thickness of the XEL-1.
In July 2008, a Japanese government body said it would fund a joint project of leading firms, which is to develop a key technology to produce large, energy-saving organic displays. The project involves one laboratory and 10 companies including Sony Corp. NEDO said the project was aimed at developing a core technology to mass-produce 40inch or larger OLED displays in the late 2010s.
In October 2008, Sony published results of research it carried out with the Max Planck Institute over the possibility of mass-market bending displays, which could replace rigid LCDs and plasma screens. Eventually, bendable, see-through displays could be stacked to produce 3D images with much greater contrast ratios and viewing angles than existing products.
Sony exhibited a 24.5″ (62cm) prototype OLED 3D television during the Consumer Electronics Show in January 2010.
In January 2011, Sony announced the PlayStation Vita handheld game console (the successor to the PSP) will feature a 5-inch OLED screen.
On February 17, 2011, Sony announced its 25″ (63.5cm) OLED Professional Reference Monitor aimed at the Cinema and high end Drama Post Production market.
On June 25, 2012, Sony and Panasonic announced a joint venture for creating low cost mass production OLED televisions by 2013.
As of 2010, LG Electronics produced one model of OLED television, the 15inch 15EL9500 and had announced a 31″ (78cm) OLED 3D television for March 2011. On December 26, 2011, LG officially announced the “world’s largest 55″ OLED panel” and featured it at CES 2012. In late 2012, LG announces the launch of the 55EM9600 OLED television in Australia.
In January 2015, LG Display signed a long term agreement with Universal Display Corporation for the supply of OLED materials and the right to use their patented OLED emitters.
Lumiotec is the first company in the world developing and selling, since January 2011, mass-produced OLED lighting panels with such brightness and long lifetime. Lumiotec is a joint venture of Mitsubishi Heavy Industries, ROHM, Toppan Printing, and Mitsui & Co. On June 1, 2011, Mitsubishi installed a 6-meter OLED ‘sphere’ in Tokyo’s Science Museum.
On January 6, 2011, Los Angeles based technology company Recom Group introduced the first small screen consumer application of the OLED at the Consumer Electronics Show in Las Vegas. This was a 2.8″ (7cm) OLED display being used as a wearable video name tag. At the Consumer Electronics Show in 2012, Recom Group introduced the world’s first video mic flag incorporating three 2.8″ (7cm) OLED displays on a standard broadcaster’s mic flag. The video mic flag allowed video content and advertising to be shown on a broadcasters standard mic flag.
BMW plans to use OLEDs in tail lights and interior lights in their future cars; however, OLEDs are currently too dim to be used for brake lights, headlights and indicators.
Research by Andre De-Guerin suggests that some newer panels now use screen printed chips connected with a continuous backplane to get around the need for a single monolithic and fragile silicon TFT. This approach is known to be used by Samsung on some of their newer phones notably the S6, Note 4 and others. It is believed that the self-assembly method used avoids the need to destroy bad backplanes as they can be pre-sorted at the manufacturing stage and the bad ICs replaced by micro-manipulators or other methods; where this is not possible the bad area can be cut off and the backplane area thus salvaged recycled for smaller displays such as on smart watches.
In 2014, Mitsubishi Chemical Corporation (MCC), a subsidiary of the Mitsubishi Chemical Holdings developed an organic light-emitting diode (OLED) panel with a life of 30,000 hours, twice that of conventional OLED panels.
The search for efficient OLED materials has been extensively supported by simulation methods. By now it is possible to calculate important properties completely computationally, independent of experimental input. This allows cost-efficient pre-screening of materials, prior to expensive synthesis and experimental characterisation.
OLED – Wikipedia
Posted: January 8, 2017 at 7:56 pm
Empowerment and a strengths perspective which support the development of innate abilities and recognize differences in a positive manner are also helping social workers increase the individual clients capacity to learn to use his or her own systems constructively
More than a simple linguistic nuance, the notion that social workers do not empower others, but instead, help people empower themselves is an ontological distinction that frames the reality experienced by both social workers and clients (Simon, 1990, p. 32, quoted in Saleeby, 2006, p. 98)
Introduction: This paper firstly looks at empowerment, what it is, and how it can assist social workers in enhancing their clients competence through development of self-efficacy, mastery, and their ability to use their own resources (both inner and outer) in a productive and beneficial manner. The paper then looks at the Strengths Perspective and how social workers can use this lens to assist clients in re-framing their sense of self, and therefore enhance their clients capacity for self-determination. The paper then looks at empowerment and the Strengths Perspective in action, through the utilization of Solution Focused theory.
In this paper it is argued that the action of empowerment is fundamental to the application of a strengths perspective. It is also argued that a positive recognition of difference, such as for those experiencing mental health issues, or who may be gay or lesbian for example, can assist clients in normalizing their lived experience.
Empowerment: Empowerment is both a theory and a practice. It is also a process as well as an outcome (Zimmerman, 1995; Gutierrez, DeLois and GlenMaye, 1995; Carr, E.S., 2003).
The practice of empowerment grew out of the womens and black rights movements of the United States in the late 60s/70s where it was recognised that these two powerless/oppressed groups did not have equal access to human services. This had a negative effect both at the level of the individual and at the level of the institution of the family, which meant that the impaired systems [were] unable to shield individuals from the negative effects of the oppressive institutions (Gutierrez et al, 1995, p. 534), thereby self-perpetuating the oppressed state of those, and other subjegated, groups.
The goal of empowerment is to increase personal, interpersonal or political power, so that individuals, families or communities can take action to improve their situation (Gutierrez et al, 1995, p. 535) Australian examples of empowered communities would include the Womens Electoral Lobby and the Tent Embassy, also developing in the 1970s for example This goal means an increase in the actual power of the client or community [as opposed to their coping with, or adaptation to, the dominant paradigm] so that action can be taken [by them] to prevent or change the problems they are facing (Gutierrez et al, 1995, p. 535). A crucial aim of empowerment is therefore enhancing the possibilities for people to control their own lives (Rappapport, 1981, p. 15) and augmenting their sense of self-determination.
The process of empowerment, involves the development of consciousness consciousness raising/conscientization, and psychological empowerment (Carr, 2003, p. 15; Zimmerman 1995) facilitating a reduction in self-blame, an assumption of personal responsibility for change, and enhancement of self-efficacy (Gutierrez et al, 1995, p. 535). Empowerment also involves the understanding by oppressed people that the nature of their oppression is structural and systemic and is not self-inflicted (Cowger, Anderson & Snively, 2006). Further, empowerment involves a commitment to challenging and combating injustice (Pease, 2002, p. 136, quoting Ward and Mullender).
Consciousness raising, practiced by many a feminist in the 1970s for example, is learning about, and increasing ones self awareness of, their individual social fit within…
Posted: January 5, 2017 at 10:45 am
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. This process occurs in all living organisms and is the basis for biological inheritance. DNA is made up of a double helix of two complementary strands. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication.
In a cell, DNA replication begins at specific locations, or origins of replication, in the genome. Unwinding of DNA at the origin and synthesis of new strands results in replication forks growing bi-directionally from the origin. A number of proteins are associated with the replication fork to help in the initiation and continuation of DNA synthesis. Most prominently, DNA polymerase synthesizes the new strands by adding nucleotides that complement each (template) strand. DNA replication occurs during the S-stage of interphase.
DNA replication can also be performed in vitro (artificially, outside a cell). DNA polymerases isolated from cells and artificial DNA primers can be used to initiate DNA synthesis at known sequences in a template DNA molecule. The polymerase chain reaction (PCR), a common laboratory technique, cyclically applies such artificial synthesis to amplify a specific target DNA fragment from a pool of DNA.
DNA usually exists as a double-stranded structure, with both strands coiled together to form the characteristic double-helix. Each single strand of DNA is a chain of four types of nucleotides. Nucleotides in DNA contain a deoxyribose sugar, a phosphate, and a nucleobase. The four types of nucleotide correspond to the four nucleobases adenine, cytosine, guanine, and thymine, commonly abbreviated as A,C, G and T. Adenine and guanine are purine bases, while cytosine and thymine are pyrimidines. These nucleotides form phosphodiester bonds, creating the phosphate-deoxyribose backbone of the DNA double helix with the nuclei bases pointing inward (i.e., toward the opposing strand). Nucleotides (bases) are matched between strands through hydrogen bonds to form base pairs. Adenine pairs with thymine (two hydrogen bonds), and guanine pairs with cytosine (stronger: three hydrogen bonds).
DNA strands have a directionality, and the different ends of a single strand are called the “3′ (three-prime) end” and the “5′ (five-prime) end”. By convention, if the base sequence of a single strand of DNA is given, the left end of the sequence is the 5′ end, while the right end of the sequence is the 3′ end. The strands of the double helix are anti-parallel with one being 5′ to 3′, and the opposite strand 3′ to 5′. These terms refer to the carbon atom in deoxyribose to which the next phosphate in the chain attaches. Directionality has consequences in DNA synthesis, because DNA polymerase can synthesize DNA in only one direction by adding nucleotides to the 3′ end of a DNA strand.
The pairing of complementary bases in DNA (through hydrogen bonding) means that the information contained within each strand is redundant. Phosphodiester (intra-strand) bonds are stronger than hydrogen (inter-strand) bonds. This allows the strands to be separated from one another. The nucleotides on a single strand can therefore be used to reconstruct nucleotides on a newly synthesized partner strand.
DNA polymerases are a family of enzymes that carry out all forms of DNA replication. DNA polymerases in general cannot initiate synthesis of new strands, but can only extend an existing DNA or RNA strand paired with a template strand. To begin synthesis, a short fragment of RNA, called a primer, must be created and paired with the template DNA strand.
DNA polymerase adds a new strand of DNA by extending the 3′ end of an existing nucleotide chain, adding new nucleotides matched to the template strand one at a time via the creation of phosphodiester bonds. The energy for this process of DNA polymerization comes from hydrolysis of the high-energy phosphate (phosphoanhydride) bonds between the three phosphates attached to each unincorporated base. Free bases with their attached phosphate groups are called nucleotides; in particular, bases with three attached phosphate groups are called nucleoside triphosphates. When a nucleotide is being added to a growing DNA strand, the formation of a phosphodiester bond between the proximal phosphate of the nucleotide to the growing chain is accompanied by hydrolysis of a high-energy phosphate bond with release of the two distal phosphates as a pyrophosphate. Enzymatic hydrolysis of the resulting pyrophosphate into inorganic phosphate consumes a second high-energy phosphate bond and renders the reaction effectively irreversible.[Note 1]
In general, DNA polymerases are highly accurate, with an intrinsic error rate of less than one mistake for every 107 nucleotides added. In addition, some DNA polymerases also have proofreading ability; they can remove nucleotides from the end of a growing strand in order to correct mismatched bases. Finally, post-replication mismatch repair mechanisms monitor the DNA for errors, being capable of distinguishing mismatches in the newly synthesized DNA strand from the original strand sequence. Together, these three discrimination steps enable replication fidelity of less than one mistake for every 109 nucleotides added.
The rate of DNA replication in a living cell was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli. During the period of exponential DNA increase at 37C, the rate was 749 nucleotides per second. The mutation rate per base pair per replication during phage T4 DNA synthesis is 1.7 per 108.
DNA replication, like all biological polymerization processes, proceeds in three enzymatically catalyzed and coordinated steps: initiation, elongation and termination.
For a cell to divide, it must first replicate its DNA. This process is initiated at particular points in the DNA, known as “origins”, which are targeted by initiator proteins. In E. coli this protein is DnaA; in yeast, this is the origin recognition complex. Sequences used by initiator proteins tend to be “AT-rich” (rich in adenine and thymine bases), because A-T base pairs have two hydrogen bonds (rather than the three formed in a C-G pair) and thus are easier to strand separate. Once the origin has been located, these initiators recruit other proteins and form the pre-replication complex, which unzips the double-stranded DNA.
DNA polymerase has 5′-3′ activity. All known DNA replication systems require a free 3′ hydroxyl group before synthesis can be initiated (note: the DNA template is read in 3′ to 5′ direction whereas a new strand is synthesized in the 5′ to 3′ directionthis is often confused). Four distinct mechanisms for DNA synthesis are recognized:
The first is the best known of these mechanisms and is used by the cellular organisms. In this mechanism, once the two strands are separated, primase adds RNA primers to the template strands. The leading strand receives one RNA primer while the lagging strand receives several. The leading strand is continuously extended from the primer by a DNA polymerase with high processivity, while the lagging strand is extended discontinuously from each primer forming Okazaki fragments. RNase removes the primer RNA fragments, and a low processivity DNA polymerase distinct from the replicative polymerase enters to fill the gaps. When this is complete, a single nick on the leading strand and several nicks on the lagging strand can be found. Ligase works to fill these nicks in, thus completing the newly replicated DNA molecule.
The primase used in this process differs significantly between bacteria and archaea/eukaryotes. Bacteria use a primase belonging to the DnaG protein superfamily which contains a catalytic domain of the TOPRIM fold type. The TOPRIM fold contains an / core with four conserved strands in a Rossmann-like topology. This structure is also found in the catalytic domains of topoisomerase Ia, topoisomerase II, the OLD-family nucleases and DNA repair proteins related to the RecR protein.
The primase used by archaea and eukaryotes, in contrast, contains a highly derived version of the RNA recognition motif (RRM). This primase is structurally similar to many viral RNA-dependent RNA polymerases, reverse transcriptases, cyclic nucleotide generating cyclases and DNA polymerases of the A/B/Y families that are involved in DNA replication and repair. In eukaryotic replication, the primase forms a complex with Pol .
Multiple DNA polymerases take on different roles in the DNA replication process. In E. coli, DNA Pol III is the polymerase enzyme primarily responsible for DNA replication. It assembles into a replication complex at the replication fork that exhibits extremely high processivity, remaining intact for the entire replication cycle. In contrast, DNA Pol I is the enzyme responsible for replacing RNA primers with DNA. DNA Pol I has a 5′ to 3′ exonuclease activity in addition to its polymerase activity, and uses its exonuclease activity to degrade the RNA primers ahead of it as it extends the DNA strand behind it, in a process called nick translation. Pol I is much less processive than Pol III because its primary function in DNA replication is to create many short DNA regions rather than a few very long regions.
In eukaryotes, the low-processivity enzyme, Pol , helps to initiate replication because it forms a complex with primase. In eukaryotes, leading strand synthesis is thought to be conducted by Pol ; however, this view has recently been challenged, suggesting a role for Pol . Primer removal is completed Pol  while repair of DNA during replication is completed by Pol .
As DNA synthesis continues, the original DNA strands continue to unwind on each side of the bubble, forming a replication fork with two prongs. In bacteria, which have a single origin of replication on their circular chromosome, this process creates a “theta structure” (resembling the Greek letter theta: ). In contrast, eukaryotes have longer linear chromosomes and initiate replication at multiple origins within these.>
The replication fork is a structure that forms within the nucleus during DNA replication. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together. The resulting structure has two branching “prongs”, each one made up of a single strand of DNA. These two strands serve as the template for the leading and lagging strands, which will be created as DNA polymerase matches complementary nucleotides to the templates; the templates may be properly referred to as the leading strand template and the lagging strand template.
DNA is always synthesized in the 5′ to 3′ direction. Since the leading and lagging strand templates are oriented in opposite directions at the replication fork, a major issue is how to achieve synthesis of nascent (new) lagging strand DNA, whose direction of synthesis is opposite to the direction of the growing replication fork.
The leading strand is the strand of nascent DNA which is being synthesized in the same direction as the growing replication fork. A polymerase “reads” the leading strand template and adds complementary nucleotides to the nascent leading strand on a continuous basis.
The lagging strand is the strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork. Because of its orientation, replication of the lagging strand is more complicated as compared to that of the leading strand. As a consequence, the DNA polymerase on this strand is seen to “lag behind” the other strand.
The lagging strand is synthesized in short, separated segments. On the lagging strand template, a primase “reads” the template DNA and initiates synthesis of a short complementary RNA primer. A DNA polymerase extends the primed segments, forming Okazaki fragments. The RNA primers are then removed and replaced with DNA, and the fragments of DNA are joined together by DNA ligase.
As helicase unwinds DNA at the replication fork, the DNA ahead is forced to rotate. This process results in a build-up of twists in the DNA ahead. This build-up forms a torsional resistance that would eventually halt the progress of the replication fork. Topoisomerases are enzymes that temporarily break the strands of DNA, relieving the tension caused by unwinding the two strands of the DNA helix; topoisomerases (including DNA gyrase) achieve this by adding negative supercoils to the DNA helix.
Bare single-stranded DNA tends to fold back on itself forming secondary structures; these structures can interfere with the movement of DNA polymerase. To prevent this, single-strand binding proteins bind to the DNA until a second strand is synthesized, preventing secondary structure formation.
Clamp proteins form a sliding clamp around DNA, helping the DNA polymerase maintain contact with its template, thereby assisting with processivity. The inner face of the clamp enables DNA to be threaded through it. Once the polymerase reaches the end of the template or detects double-stranded DNA, the sliding clamp undergoes a conformational change that releases the DNA polymerase. Clamp-loading proteins are used to initially load the clamp, recognizing the junction between template and RNA primers.:274-5
At the replication fork, many replication enzymes assemble on the DNA into a complex molecular machine called the replisome. The following is a list of major DNA replication enzymes that participate in the replisome:
Replication machineries consist of factors involved in DNA replication and appearing on template ssDNAs. Replication machineries include primosotors are replication enzymes; DNA polymerase, DNA helicases, DNA clamps and DNA topoisomerases, and replication proteins; e.g. single-stranded DNA binding proteins (SSB). In the replication machineries these components coordinate. In most of the bacteria, all of the factors involved in DNA replication are located on replication forks and the complexes stay on the forks during DNA replication. These replication machineries are called replisomes or DNA replicase systems. These terms are generic terms for proteins located on replication forks. In eukaryotic and some bacterial cells the replisomes are not formed.
Since replication machineries do not move relatively to template DNAs such as factories, they are called a replication factory. In an alternative figure, DNA factories are similar to projectors and DNAs are like as cinematic films passing constantly into the projectors. In the replication factory model, after both DNA helicases for leading strands and lagging strands are loaded on the template DNAs, the helicases run along the DNAs into each other. The helicases remain associated for the remainder of replication process. Peter Meister et al. observed directly replication sites in budding yeast by monitoring green fluorescent protein(GFP)-tagged DNA polymerases . They detected DNA replication of pairs of the tagged loci spaced apart symmetrically from a replication origin and found that the distance between the pairs decreased markedly by time. This finding suggests that the mechanism of DNA replication goes with DNA factories. That is, couples of replication factories are loaded on replication origins and the factories associated with each other. Also, template DNAs move into the factories, which bring extrusion of the template ssDNAs and nascent DNAs. Meisters finding is the first direct evidence of replication factory model. Subsequent research has shown that DNA helicases form dimers in many eukaryotic cells and bacterial replication machineries stay in single intranuclear location during DNA synthesis.
The replication factories perform disentanglement of sister chromatids. The disentanglement is essential for distributing the chromatids into daughter cells after DNA replication. Because sister chromatids after DNA replication hold each other by Cohesin rings, there is the only chance for the disentanglement in DNA replication. Fixing of replication machineries as replication factories can improve the success rate of DNA replication. If replication forks move freely in chromosomes, catenation of nuclei is aggravated and impedes mitotic segregation.
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome; these are not known to be regulated in any particular way. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes, but ends at the telomere region of repetitive DNA close to the ends. This shortens the telomere of the daughter DNA strand. Shortening of the telomeres is a normal process in somatic cells. As a result, cells can only divide a certain number of times before the DNA loss prevents further division. (This is known as the Hayflick limit.) Within the germ cell line, which passes DNA to the next generation, telomerase extends the repetitive sequences of the telomere region to prevent degradation. Telomerase can become mistakenly active in somatic cells, sometimes leading to cancer formation. Increased telomerase activity is one of the hallmarks of cancer.
Termination requires that the progress of the DNA replication fork must stop or be blocked. Termination at a specific locus, when it occurs, involves the interaction between two components: (1) a termination site sequence in the DNA, and (2) a protein which binds to this sequence to physically stop DNA replication. In various bacterial species, this is named the DNA replication terminus site-binding protein, or Ter protein.
Because bacteria have circular chromosomes, termination of replication occurs when the two replication forks meet each other on the opposite end of the parental chromosome. E. coli regulates this process through the use of termination sequences that, when bound by the Tus protein, enable only one direction of replication fork to pass through. As a result, the replication forks are constrained to always meet within the termination region of the chromosome.
Within eukaryotes, DNA replication is controlled within the context of the cell cycle. As the cell grows and divides, it progresses through stages in the cell cycle; DNA replication takes place during the S phase (synthesis phase). The progress of the eukaryotic cell through the cycle is controlled by cell cycle checkpoints. Progression through checkpoints is controlled through complex interactions between various proteins, including cyclins and cyclin-dependent kinases. Unlike bacteria, eukaryotic DNA replicates in the confines of the nucleus.
The G1/S checkpoint (or restriction checkpoint) regulates whether eukaryotic cells enter the process of DNA replication and subsequent division. Cells that do not proceed through this checkpoint remain in the G0 stage and do not replicate their DNA.
Replication of chloroplast and mitochondrial genomes occurs independently of the cell cycle, through the process of D-loop replication.
In vertebrate cells, replication sites concentrate into positions called replication foci. Replication sites can be detected by immunostaining daughter strands and replication enzymes and monitoring GFP-tagged replication factors. By these methods it is found that replication foci of varying size and positions appear in S phase of cell division and their number per nucleus is far smaller than the number of genomic replication forks.
P. Heun et al.(2001) tracked GFP-tagged replication foci in budding yeast cells and revealed that replication origins move constantly in G1 and S phase and the dynamics decreased significantly in S phase. Traditionally, replication sites were fixed on spatial structure of chromosomes by nuclear matrix or lamins. The Heuns results denied the traditional concepts, budding yeasts don’t have lamins, and support that replication origins self-assemble and form replication foci.
By firing of replication origins, controlled spatially and temporally, the formation of replication foci is regulated. D. A. Jackson et al.(1998) revealed that neighboring origins fire simultaneously in mammalian cells. Spatial juxtaposition of replication sites brings clustering of replication forks. The clustering do rescue of stalled replication forks and favors normal progress of replication forks. Progress of replication forks is inhibited by many factors; collision with proteins or with complexes binding strongly on DNA, deficiency of dNTPs, nicks on template DNAs and so on. If replication forks stall and the remaining sequences from the stalled forks are not replicated, the daughter strands have nick obtained un-replicated sites. The un-replicated sites on one parent’s strand hold the other strand together but not daughter strands. Therefore, the resulting sister chromatids cannot separate from each other and cannot divide into 2 daughter cells. When neighboring origins fire and a fork from one origin is stalled, fork from other origin access on an opposite direction of the stalled fork and duplicate the un-replicated sites. As other mechanism of the rescue there is application of dormant replication origins that excess origins don’t fire in normal DNA replication.
Most bacteria do not go through a well-defined cell cycle but instead continuously copy their DNA; during rapid growth, this can result in the concurrent occurrence of multiple rounds of replication. In E. coli, the best-characterized bacteria, DNA replication is regulated through several mechanisms, including: the hemimethylation and sequestering of the origin sequence, the ratio of adenosine triphosphate (ATP) to adenosine diphosphate (ADP), and the levels of protein DnaA. All these control the binding of initiator proteins to the origin sequences.
Because E. coli methylates GATC DNA sequences, DNA synthesis results in hemimethylated sequences. This hemimethylated DNA is recognized by the protein SeqA, which binds and sequesters the origin sequence; in addition, DnaA (required for initiation of replication) binds less well to hemimethylated DNA. As a result, newly replicated origins are prevented from immediately initiating another round of DNA replication.
ATP builds up when the cell is in a rich medium, triggering DNA replication once the cell has reached a specific size. ATP competes with ADP to bind to DnaA, and the DnaA-ATP complex is able to initiate replication. A certain number of DnaA proteins are also required for DNA replication each time the origin is copied, the number of binding sites for DnaA doubles, requiring the synthesis of more DnaA to enable another initiation of replication.
Researchers commonly replicate DNA in vitro using the polymerase chain reaction (PCR). PCR uses a pair of primers to span a target region in template DNA, and then polymerizes partner strands in each direction from these primers using a thermostable DNA polymerase. Repeating this process through multiple cycles amplifies the targeted DNA region. At the start of each cycle, the mixture of template and primers is heated, separating the newly synthesized molecule and template. Then, as the mixture cools, both of these become templates for annealing of new primers, and the polymerase extends from these. As a result, the number of copies of the target region doubles each round, increasing exponentially.
DNA replication – Wikipedia
Posted: January 4, 2017 at 6:22 pm
Leagues and results
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