Math Is Fun Forum

2433) Ammonium Nitrate

Gist

Ammonium nitrate is a white, crystalline, water-soluble salt primarily used as a high-nitrogen fertilizer and as a key component in commercial explosives. It is a strong oxidizer that contains both a fuel and an oxygen-producing agent, making it potentially explosive, especially when mixed with a fuel or subjected to heat. Due to its hazardous nature, there are strict regulations surrounding its production, storage, and use.

Ammonium nitrate is primarily used as a component in fertilizers for agriculture and in the manufacture of explosives for mining, quarrying, and construction. It also has niche applications, such as in instant cold packs and as a source for medical-grade nitrous oxide (laughing gas). 

Summary

Ammonium nitrate is a chemical compound with the formula NH4NO3. It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, but does not form hydrates. It is predominantly used in agriculture as a high-nitrogen fertilizer.

Its other major use is as a component of explosive mixtures used in mining, quarrying, and civil construction. It is the major constituent of ANFO, an industrial explosive which accounts for 80% of explosives used in North America; similar formulations have been used in improvised explosive devices.

Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse. Accidental ammonium nitrate explosions have killed thousands of people since the early 20th century. Global production was estimated at 21.6 million tonnes in 2017. By 2021, global production of ammonium nitrate was down to 16.7 million tonnes.

(ANFO or AN/FO, for ammonium nitrate/fuel oil).

Details

Ammonium nitrate, (NH4NO3), is a salt of ammonia and nitric acid, used widely in fertilizers and explosives. The commercial grade contains about 33.5 percent nitrogen, all of which is in forms utilizable by plants; it is the most common nitrogenous component of artificial fertilizers. Ammonium nitrate also is employed to modify the detonation rate of other explosives, such as nitroglycerin in the so-called ammonia dynamites, or as an oxidizing agent in the ammonals, which are mixtures of ammonium nitrate and powdered aluminum.

Ammonium nitrate is a colourless crystalline substance (melting point 169.6 °C [337.3 °F]). It is highly soluble in water; heating of the water solution decomposes the salt to nitrous oxide (laughing gas). Because solid ammonium nitrate can undergo explosive decomposition when heated in a confined space, government regulations have been imposed on its shipment and storage.

Additional Information

Ammonium nitrate, in terms of quantity at least, is the most commonly used oxidizer in improvised explosive mixtures. The salt has been used in many terrorist attacks, particularly those involving large charge weights of over half a tonne. Ammonium nitrate has been mixed with a number of fuels such as sugar and aluminum.

Ammonium nitrate is the main component of slurry explosives used for mining. However, the source of ammonium nitrate used for improvised explosive mixtures is often fertilizer. Fertilizer-grade ammonium nitrate can be powdered or in the form of prills. Fertilizer-grade prills are usually coated to reduce hygroscopicity. However, as prills or powder, fertilizer-grade ammonium nitrate can be mixed with suitable fuels, such as sugar or fuel oil, to produce an effective high explosive. The detonability and explosive power of ammonium nitrate-based improvised explosives is dependent on the particle size, the fuel, stoichiometry, degree of mixing, the packing density, and the degree of confinement. In prill form, the explosive is not usually detonable and requires a booster charge for efficient detonation and complete reaction. It acts as a tertiary explosive. In powdered form, it is often detonable.

Explosive mixtures incorporating ammonium nitrate have large critical diameters and are therefore nonideal explosives, whose energy release during detonation occurs in a time scale insufficient for the majority of it to keep up with the shock front. The loss of energy from the system exceeds the rate of generation and a self-sustaining reaction cannot be maintained. The explosive fails to react completely and can fail to detonate; therefore, large charge weights are often necessary for reliable detonation. Furthermore, in contrast to ideal explosives, confinement has a significant effect on detonation, increased confinement resulting in an increased velocity of detonation (VoD).

Improvised explosives incorporating ammonium nitrate have detonation velocities in the range of 1400–6000 m/s. The TNT equivalence of ammonium nitrate-based improvised explosives ranges from 25% to 100% depending on the factors referred to earlier, for example, packing density and degree of confinement.

Fuels mixed with ammonium nitrate to produce effective improvised high explosives have included sugar, fuel oil, aluminum, nitromethane, and nitrobenzene.

Research has shown that most ammonium nitrate-based improvised explosives are chemically and thermally stable and insensitive to stimuli, friction, impact, and ESD in normal conditions. However, mixtures with aluminum have been found to be sensitive to ESD.

The potential for ammonium nitrate to decompose at temperatures above 200 °C and, as a result of the heat generated by decomposition, to then undergo a runaway reaction is well known. While many fuels have been shown to lower the decomposition temperature, mixtures have, nevertheless, been shown to be relatively thermally stable during storage and handling.

(ESD: Electrostatic discharge).

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#6287.

2380) Marshall Warren Nirenberg

Gist:

Work

In the 1950s, it was established that genetic information is transferred from DNA to RNA, to protein. One sequence of three nucleotides in DNA corresponds to a certain amino acid within a protein. How could this genetic code be cracked? Marshall Nirenberg and Heinrich Matthaei produced a long RNA chain consisting of a single nucleotide. When this resulted in a long chain of a single amino acid, the first part of the genetic code puzzle fell into place. The remainder of the code was mapped out in the years that followed.

Summary

Marshall Warren Nirenberg (born April 10, 1927, New York, N.Y., U.S.—died Jan. 15, 2010, New York) was an American biochemist and corecipient, with Robert William Holley and Har Gobind Khorana, of the 1968 Nobel Prize for Physiology or Medicine. He was cited for his role in deciphering the genetic code. He demonstrated that, with the exception of “nonsense codons,” each possible triplet (called a codon) of four different kinds of nitrogen-containing bases found in deoxyribonucleic acid (DNA) and, in some viruses, in ribonucleic acid (RNA) ultimately causes the incorporation of a specific amino acid into a cell protein. Nirenberg’s work and that of Holley and Khorana helped to show how genetic instructions in the cell nucleus control the composition of proteins.

Nirenberg earned a B.S. (1948) in zoology and chemistry and an M.S. (1952) in zoology at the University of Florida. He received a Ph.D. in biological chemistry from the University of Michigan in 1957 and that year joined the staff of the National Institutes of Health (NIH) in Bethesda, Md. His research earned him the National Medal of Science in 1964, and the following year he was elevated to director of biochemical genetics at the NIH, a position he held for the remainder of his career. In 1968 Nirenberg and Khorana were recognized with an Albert Lasker Basic Medical Research Award and the Louisa Gross Horowitz Prize for Biology or Biochemistry.

In the late 1960s Nirenberg’s research shifted from genetics to neurobiology. He began investigating neuroblastomas—tumours involving masses of neurons, known as ganglia—and eventually developed a neuroblastoma model that served as the basis for a broad range of neurobiological research. In the 1970s Nirenberg used his model as a platform for explorations into morphine’s effects on the nervous system and neural synapse formation in chicken retinas. During this time scientists discovered that under the influence of certain factors normal genes could be “switched on,” becoming overactive in the form of oncogenes (cancer-causing genes). This finding, which demonstrated that gene activity could change and that these changes could affect cell growth, stimulated Nirenberg’s interest. His research had begun to focus on nervous system growth and development, but how these processes were controlled was unknown. Nirenberg reasoned that to further understand the development of the nervous system, it was necessary to understand the genes that had the greatest influence on neurological development in the embryo. By the late 1980s a set of genes, known as homeobox genes (discovered in 1983), had become central to his studies. His experiments concerning homeobox genes and the assembly of the nervous system in Drosophila (fruit fly) were crucial to the advancement of the field of neurobiology. Much of Nirenberg’s work on nervous system development in Drosophila proved relevant to studies on the development of the nervous system in humans.

Details

Marshall Warren Nirenberg (April 10, 1927 – January 15, 2010) was an American biochemist and geneticist. He shared a Nobel Prize in Physiology or Medicine in 1968 with Har Gobind Khorana and Robert W. Holley for "breaking the genetic code" and describing how it operates in protein synthesis. In the same year, together with Har Gobind Khorana, he was awarded the Louisa Gross Horwitz Prize from Columbia University.

Biography

Nirenberg was born in New York City to a Jewish family, the son of Minerva (Bykowsky) and Harry Edward Nirenberg, a shirtmaker. He developed rheumatic fever as a boy, so the family moved to Orlando, Florida to take advantage of the subtropical climate. He developed an early interest in biology. In 1948 he received his BS degree, and in 1952, a master's degree in zoology from the University of Florida at Gainesville where he was also a member of the Pi Lambda Phi Fraternity. His dissertation for the Master's thesis was an ecological and taxonomic study of caddis flies (Trichoptera). He received his PhD in biochemistry from the University of Michigan, Ann Arbor in 1957, studying hexose uptake in tumor cells with his advisor James F. Hogg.

He began his postdoctoral work at the National Institutes of Health (NIH) in 1957 as a fellow of the American Cancer Society in what was then called the National Institute of Arthritis and Metabolic Diseases. In 1959 he became a research biochemist at the NIH and began to study the steps that relate DNA, RNA and protein. Nirenberg's groundbreaking experiments advanced him to become the head of the Section of Biochemical Genetics in 1962 in the National Heart Institute (now the National Heart, Lung, and Blood Institute), where he remained a laboratory chief until his death. Fellow laboratory chiefs included Ernst Freese and Daniel Carleton Gajdusek. He was married in 1961 to Perola Zaltzman, a chemist from the University of Brazil, Rio de Janeiro, who also worked at NIH and died in 2001. Nirenberg married Myrna Weissman, PhD, Professor of Epidemiology and Psychiatry at Columbia University College of Physicians and Surgeons in 2005. He had four stepchildren: Susan Weissman of Evanston, Illinois, Judith Weissman of New York, New York, Sharon Weissman of New Haven, Connecticut, and Jonathan Weissman of San Francisco, California. He was also survived by his sister, Joan Nirenberg Geiger of Dallas, Texas, several nieces and a nephew.

Nirenberg was awarded the National Medal of Science in 1964 and the National Medal of Honor in 1968 by President Lyndon B. Johnson. In 1981, Nirenberg became a founding member of the World Cultural Council. In 1986, Nirenberg's achievements and contributions to the field of biochemistry genetics was recognized at an event honoring Maimonides and Menachem M. Schneerson, in the nation's capital, hosted by Bob Dole and Joe Biden. He was elected to the American Philosophical Society in 2001. He died on January 15, 2010, from cancer after several months of illness.

Research

By 1958, experiments and analysis such as the Avery–MacLeod–McCarty experiment, the Hershey–Chase experiment, the Watson–Crick structure and the Meselson–Stahl experiment had shown DNA to be the molecule of genetic information. It was not known, however, how DNA directed the expression of proteins, or what role RNA had in these processes. Nirenberg teamed up with Heinrich J. Matthaei at the National Institutes of Health to answer these questions. They produced RNA composed solely of uracil, a nucleotide that only occurs in RNA. They then added this synthetic poly-uracil RNA into a cell-free extract of Escherichia coli which contained the DNA, RNA, ribosomes and other cellular machinery for protein synthesis. They added DNase, which breaks apart the DNA, so that no additional proteins would be produced other than that from their synthetic RNA. They then added 1 radioactively labeled amino acid, the building blocks of proteins, and 19 unlabeled amino acids to the extract, varying the labeled amino acid in each sample. Only in the extract containing the radioactively labeled phenylalanine, was the resulting protein also radioactive. This implied that the genetic code for phenylalanine on RNA consisted of a repetition of uracil bases. Indeed, as we know now, it is UUU (three uracil bases in a row). This was the first step in deciphering the codons of the genetic code and the first demonstration of messenger RNA (see Nirenberg and Matthaei experiment).

In August 1961, at the International Congress of Biochemistry in Moscow, Nirenberg presented a paper to a small group of scientists, reporting the decoding of the first codon of the genetic code. Matthew Meselson, who was in the audience, spontaneously hugged Nirenberg at the end of the talk and then told Francis Crick about Nirenberg's result. Crick invited Nirenberg to repeat his performance the next day in a talk to a much larger audience. Speaking before the assembled congress of more than a thousand people, Nirenberg electrified the scientific community. He quickly received great scientific attention for these experiments. Within a few years, his research team had performed similar experiments and found that three-base repeats of adenosine (AAA) produced the amino acid lysine, and cytosine repeats (CCC) produced proline. The next breakthrough came when Philip Leder, a postdoctoral researcher in Nirenberg's lab, developed a method for determining the genetic code on pieces of tRNA (see Nirenberg and Leder experiment). This greatly sped up the assignment of three-base codons to amino acids so that 50 codons were identified in this way. Khorana's experiments confirmed these results and completed the genetic code translation.

The period between 1961 and 1962 is often referred to as the "coding race" because of the competition between the labs of Nirenberg at NIH and Nobel laureate Severo Ochoa at New York University Medical School, who had a massive staff. Faced with the possibility of helping the first NIH scientist win a Nobel prize, many NIH scientists put aside their own work to help Nirenberg in deciphering the mRNA codons for amino acids. Dr. DeWitt Stetten, Jr., director of the National Institute of Arthritis and Metabolic Diseases, called this period of collaboration "NIH's finest hour".

Nirenberg's later research focused on neuroscience, neural development, and the homeobox genes.

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#2512. What does the medical term Chronic traumatic encephalopathy mean?

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#6286.

2379) Robert W. Holley

Gist:

Work

In the 1950s, it was established that genetic information is transferred from DNA to RNA, to protein. A sequence of three nucleotides in DNA–known as a codon–corresponds to a particular amino acid in a protein. The proteins are formed in what are known as ribosomes, which lie outside the cell nucleus. The transportation of amino acids to these ribosomes takes place with the help of a particular kind of RNA called transfer RNA or tRNA. There exists a special tRNA molecule for each codon. Robert Holley was the first person to successfully isolate tRNA and, in 1964, was also able to map its structure.

Summary

Robert William Holley (born Jan. 28, 1922, Urbana, Ill., U.S.—died Feb. 11, 1993, Los Gatos, Calif.) was an American biochemist who shared the Nobel Prize in Physiology or Medicine in 1968 with Marshall Warren Nirenberg and Har Gobind Khorana. Their research helped explain how the genetic code controls the synthesis of proteins.

Holley obtained his Ph.D. in organic chemistry from Cornell University, Ithaca, N.Y., in 1947. He investigated a variety of biochemical questions at the state and federal agricultural experiment stations at Cornell (1948–64). He began his research on RNA after spending a year studying with James F. Bonner at the California Institute of Technology (1955–56).

By 1960 Holley and others had shown that small molecules of ribonucleic acids, called transfer RNAs, were involved in the assembly of amino acids into proteins. Holley and his collaborators developed techniques to separate the different transfer RNAs from the mixture in the cell. By 1965 he had determined the composition of the transfer RNA that incorporates the amino acid alanine into protein molecules. This feat—the first determination of the sequence of nucleotides in a nucleic acid—required digesting the molecule with enzymes, identifying the pieces, then figuring out how they fit together. It has since been shown that all transfer RNAs have similar structures.

In 1968 Holley became a resident fellow at the Salk Institute for Biological Studies in La Jolla, Calif. He also became an adjunct professor at the University of California, San Diego, in the following year.

Details

Robert William Holley (January 28, 1922 – February 11, 1993) was an American biochemist. He shared the Nobel Prize in Physiology or Medicine in 1968 (with Har Gobind Khorana and Marshall Warren Nirenberg) for describing the structure of alanine transfer RNA, linking DNA and protein synthesis.

Holley was born in Urbana, Illinois, and graduated from Urbana High School in 1938. He went on to study chemistry at the University of Illinois at Urbana-Champaign, graduating in 1942 and commencing his PhD studies in organic chemistry at Cornell University. During World War II Holley spent two years working under Professor Vincent du Vigneaud at Cornell University Medical College, where he was involved in the first chemical synthesis of penicillin. Holley completed his PhD studies in 1947.

Following his graduate studies Holley remained associated with Cornell. He became an assistant professor of organic chemistry in 1948, and was appointed as professor of biochemistry in 1962. He began his research on RNA after spending a year's sabbatical (1955–1956) studying with James F. Bonner at the California Institute of Technology.

Holley's research on RNA focused first on isolating transfer RNA (tRNA), and later on determining the sequence and structure of alanine tRNA, the molecule that incorporates the amino acid alanine into proteins. Holley's team of researchers determined the tRNA's structure by using two ribonucleases to split the tRNA molecule into pieces. Each enzyme split the molecule at location points for specific nucleotides. By a process of "puzzling out" the structure of the pieces split by the two different enzymes, then comparing the pieces from both enzyme splits, the team eventually determined the entire structure of the molecule. The group of researchers include Elizabeth Beach Keller, who developed the cloverleaf model that describes transfer RNA, during the course of the research.

The structure was completed in 1964, and was a key discovery in explaining the synthesis of proteins from messenger RNA. It was also the first nucleotide sequence of a ribonucleic acid ever determined. Holley was awarded the Nobel Prize in Physiology or Medicine in 1968 for this discovery, and Har Gobind Khorana and Marshall W. Nirenberg were also awarded the prize that year for contributions to the understanding of protein synthesis.

Using the Holley team's method, other scientists determined the structures of the remaining tRNA's. A few years later the method was modified to help track the sequence of nucleotides in various bacterial, plant, and human viruses. He died in 1993.

In 1968 Holley became a resident fellow at the Salk Institute for Biological Studies in La Jolla, California.

According to the New York Times obituary, "He was an avid outdoorsman and an amateur sculptor of bronze." His widow Ann died in 1996.

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#10639. What does the term in Biology Ecotype mean?

#10640. What does the term in Biology Ectoderm mean?

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#2511. What does the medical term Menopause mean?