A couplet is a pair of successive lines of metre in poetry. A couplet consists of two successive lines that rhyme and have the same metre. A couplet may be run-on. In a formal couplet, each of the two lines is end-stopped, implying that there is a grammatical pause at the end of a line of verse. In a run-on couplet, the meaning of the first line continues to the second; the word "couplet" comes from the French word meaning "two pieces of iron riveted or hinged together." The term "couplet" was first used to describe successive lines of verse in Sir P. Sidney's Arcadia in 1590: "In singing some short coplets, whereto the one halfe beginning, the other halfe should answere."While couplets traditionally rhyme, not all do. Poems may use white space to mark out couplets. Couplets in iambic pentameter are called heroic couplets. John Dryden in the 17th century and Alexander Pope in the 18th century were both well known for their writing in heroic couplets; the Poetic epigram is in the couplet form. Couplets can appear as part of more complex rhyme schemes, such as sonnets.

Rhyming couplets are one of the simplest rhyme schemes in poetry. Because the rhyme comes so it tends to call attention to itself. Good rhyming couplets tend to "explode" as both the rhyme and the idea come to a quick close in two lines. Here are some examples of rhyming couplets where the sense as well as the sound "rhymes": True wit is nature to advantage dress'd. -- Alexander PopeWhether or not we find what we are seeking Is idle. — Edna St. Vincent Millay On the other hand, because rhyming couplets have such a predictable rhyme scheme, they can feel artificial and plodding. Here is a Pope parody of the predictable rhymes of his era: Where-e'er you find "the cooling western breeze," In the next line, it "whispers through the trees. Rhyming couplets are used in Early Modern English poetry, as seen in Chaucer's The Canterbury Tales; this work of literature is written entirely in rhyming couplets. Shakespearean sonnets employ rhyming couplets at the end to emphasize the theme. Take one of Shakespeare's most famous sonnets, Sonnet 18, for example: Shall I compare thee to a summer's day?

Thou art more lovely and more temperate: Rough winds do shake the darling buds of May, And summer's lease hath all too short a date: Sometimes too hot the eye of heaven shines, And is his gold complexion dimm'd. Chinese couplets or "contrapuntal couplets" may be seen on doorways in Chinese communities worldwide. Couplets displayed as part of the Chinese New Year festival, on the first morning of the New Year, are called chunlian; these are purchased at a market a few days before and glued to the doorframe. The text of the couplets is traditional and contains hopes for prosperity. Other chunlian reflect more recent concerns. For example, the CCTV New Year's Gala promotes couplets reflecting current political themes in mainland China; some Chinese couplets may consist of two lines of four characters each. Couplets are read from top to bottom, but is a 6 word diagraph with 19 lines Tamil literature contains some of the best known examples of ancient couplet poetry. The Tamil language has a rich and refined grammar for couplet poetry, distichs in Tamil poetry follow the venpa metre.

The most famous example for Tamil couplet poetry is the ancient Tamil moral text of Tirukkural, which contains a total of 1330 couplets written in the kural venpa metre from which the title of the work was derived centuries later. Each Kural couplet is made of 7 words—4 in the first line and 3 in the second; the first word may rhyme with the fifth word. Below is an example of a couplet: இலன்என்று தீயவை செய்யற்க செய்யின் இலனாகும் மற்றும் பெயர்த்து. Transliteration: Ilan endru theeyavai seyyarkka seyyin Ilanaagum matrum peyartthuTranslation: Make not thy poverty a plea for ill; the American poet J. V. Cunningham was noted for many distichs included in the various forms of epigrams included in his poetry collections, as exampled here: Deep summer, time passes. Sorrow wastesTo a new sorrow. While Time heals time hastes Antithetical couplet Biblical poetry Chastushka Closed couplet Coupletist Distich Elegiac couplet Kabirdas Monostich Parallelism Tristich

Mitomycin C is a mitomycin, used as a chemotherapeutic agent by virtue of its antitumour activity. It is given intravenously to treat upper gastro-intestinal cancers, anal cancers, breast cancers, as well as by bladder instillation for superficial bladder tumours, it causes delayed bone marrow toxicity and therefore it is administered at 6-weekly intervals. Prolonged use may result in permanent bone-marrow damage, it may cause lung fibrosis and renal damage. Mitomycin C has been used topically rather than intravenously in several areas; the first is cancers bladder cancers and intraperitoneal tumours. It is now well known that a single instillation of this agent within 6 hours of bladder tumor resection can prevent recurrence; the second is in eye surgery where mitomycin C 0.02% is applied topically to prevent scarring during glaucoma filtering surgery and to prevent haze after PRK or LASIK. The third is in esophageal and tracheal stenosis where application of mitomycin C onto the mucosa following dilatation will decrease re-stenosis by decreasing the production of fibroblasts and scar tissue.

Mitomycin C is a potent DNA crosslinker. A single crosslink per genome has shown to be effective in killing bacteria; this is accomplished by reductive activation of mitomycin to form a mitosene, which reacts successively via N-alkylation of two DNA bases. Both alkylations are sequence specific for a guanine nucleoside in the sequence 5'-CpG-3'. Potential bis-alkylating heterocylic quinones were synthetised in order to explore their antitumoral activities by bioreductive alkylation. Mitomycin is used as a chemotherapeutic agent in glaucoma surgery. In the bacterium Legionella pneumophila, mitomycin C induces competence, a condition necessary for the process of natural transformation that transfers DNA and promotes recombination between cells. Exposure of the fruitfly Drosophila melanogaster to mitomycin C increases recombination during meiosis, a key stage of the sexual cycle, it has been suggested that during sexual process in prokaryotes and eukaryotes DNA cross-links and other damages introduced by mitomycin C may be removed by recombinational repair.

Anticancer treatments with chemotherapeutic agents impair brain cell function leading to memory loss and cognitive dysfunction. In order to understand the basis of these impairments, mice were treated with mitomycin C, a chemotherapeutic agent, cells of the prefrontal cortex were examined; this treatment resulted in an increase of the oxidative DNA damage 8-oxo-dG, a decrease in the enzyme OGG1 that ordinarily repairs such damage and epigenetic alterations. These alterations at the DNA level may explain, at least in part, the impairments of cognitive function after chemotherapy. Mitomycin was discovered in the 1950s by Japanese scientists in cultures of the microorganism Streptomyces caespitosus. Aziridine

4-Amino-2-methyl-1-naphthol is a menadione analog. Its hydrochloride salt is called vitamin K5; the HCl salt has been used as a medicine for vitamin K deficiency under tradenames such as Synkamin, sold by Parke-Davis, but has since been discontinued. Vitamin K function of the compound was first noted in 1940. Oral lethal dose for the HCl salt in rats is 0.7 g/kg. 4-Amino-2-methyl-1-naphthol HCl salt is a vitamin K and prevents bleeding caused by vitamin K deficiency when given via intravenous or intramuscular injections at doses of about 1–3 mg. HCl salt is water-soluble and its parenteral administration requires no emulsifiers unlike fat-soluble phylloquinone for example, in formulations with lecithin or glycocholic acid. Parenterally given 1 mg/ml aqueous solutions and orally taken 4 mg tablets of the HCl salt have been available commercially. 4-Amino-2-methyl-1-naphthol HCl salt has a mass of 209.57 g/mol. It darkens at 262 °C and decays without melting at 280–282 °C. HCl salt breaks down in aqueous solutions via oxidation, quite fast at neutral pH.

First a pink and a purple precipitant forms. The colored precipitant is -2-methyl-1,4-naphthoquinone, a condensation reaction product of 4-amino-2-methyl-1-naphthol and menadione. Latter is formed via oxidation and deamination of 4-amino-2-methyl-1-naphthol.4-Amino-2-methyl-1-naphthol can be made from 2-methylnaphthalene or menadione. 4-Amino-2-methyl-1-naphthol HCl salt prevents the growth of different bacteria. Thus it has been studied as potential food preservative. HCl salt has been studied as a potential treatment for cancer as it prevents glycolysis in cancer cells, which provides them energy for growth