Chemistry

Proteolytic cleavage

Proteolytic cleavage


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Serine protease inhibitors

The reaction with diisopropyl fluorophosphate (DIPF) is considered a diagnostic test for the presence of an active serine residue in serine proteases such as chymotrypsin or acetylcholine esterase. The enzyme is irreversibly inhibited because DIPF has a tetrahedral phosphate group, which is an analogue to the transition state in catalysis and thus occupies the space for the substrate. Due to the organic phosphate group and its irreversible inhibitory effect on acetylcholine esterase, DIPF acts as a strong neurotoxin.


The inactive proenzyme trypsinogen is the precursor of the protein-splitting digestive enzyme trypsin. Trypsinogen is secreted in the pancreas and activated in the duodenum by a membrane-bound enterokinase. This is done by proteolytic cleavage, in which the enterokinase cleaves the hexapeptide (Val-Asp-Asp-Asp-Asp-Lys) from the inactive enzyme precursor trypsinogen. The protein-splitting enzyme trypsin is in turn involved in digestive processes by catalyzing the proteolytic cleavage of trypsinogen into trypsin and is responsible for the proteolytic cleavage of chymotrypsin and procarboxypeptidase.

Mutations of the cationic trypsinogen are found in patients with chronic non-alcoholic pancreatitis, although a clear autosomal dominant inheritance could not be documented. Other point mutations that were found in the screening of relatives of index patients are L104P, R116C, and C139F. However, the importance of these trypsinogen mutants should not be overestimated, since no mutation could be detected in 69.4 percent of the index patients from families with hereditary pancreatitis. As before, a careful clinical examination and a family history collection is indicated if there is any suspicion, and not the search for genetic variants. & # 911 & # 93


What is nuclear fusion?

Nuclear fusion is the fusion of two or more atoms into one larger one. This type of reaction allows atoms to combine to produce a larger atom with a higher atomic number. One way to do a nuclear fusion is to keep two or more nuclei close together, causing a reaction where the atoms stick together and combine into one.

In addition, nuclear fusion occurs naturally in nature. A good example are the stars in the galaxy. Theories suggest that millions of stars have joined together to form one giant massive star that we now refer to as the sun.


Cleavage

By thermal neutrons

Usually only isotopes with an odd number of neutrons can be split well by thermal neutrons, since only they can be split by absorbing a neutron Couple energy (see droplet model).

Americium, as the 95th element, has an even number of neutrons with its odd number of protons for odd numbers of nucleons, while plutonium, as the 94th element, with its even number of protons for odd numbers of nucleons also has odd numbers of neutrons. This is why americium 241 Am, in contrast to plutonium 241 Pu, is difficult to cleave.

By very fast neutrons

Very fast neutrons can also split isotopes with an even number of neutrons that do not gain any pair energy by absorbing a neutron.

The three-stage bomb can be used as a practical example, in which very fast neutrons (over 14 MeV), which were generated during nuclear fusion, split the uranium 238 U nuclei in the bomb shell made of depleted uranium, thereby greatly increasing the explosive power of the bomb and the fallout .


Nuclear fission and nuclear fusion

Difficulty level: medium-difficult task

a) Give the decay equation for the & ldquosuper-asymmetric splitting of the (<> _ <> ^ <232> < rm> ) Core. (3 BE)

b) Calculate the total energy (Q ) in (< rm) that is released> ). (7 BE)

c) (<> _ <> ^ <232> < rm> ) can also result in the same end product (<> _ <> ^ <208> < rm> ) convert.

Calculate how many α and how many β decays are necessary for this.

Explain, without calculation, why significantly less energy is released than with the & quot; super-asymmetric cleavage & quot ;. (6 BE)

d) The speed of the two decay products of a previously resting (<> _ <> ^ <232> < rm> ) - atom in the & quot; super-asymmetric cleavage & quot; should be calculated.

To do this, set up the corresponding equations, but do not perform any calculation. (6 BE)

Note: The atomic masses given here were taken from the AME2016 of the AMDC-Atomic Mass Data Center.


Projects

Body odors are influenced by various factors such as age, gender and the emotional and physiological state of the person, as well as by the use of personal care products and clothing. While the field of chemical communication in the field of psychology has existed for a long time and is currently experiencing an upswing, there is a lack of research groups that can provide the necessary chemical analysis. A suitable analysis is to be established in this project at the Erlangen location together with the points of contact for data analysis and microbiology in order to be able to answer further research questions on the individuality and short-term or long-term variability of odor signatures, e.g. in the course of physiological changes.

Additional Information

Completed Projects

Chemistry in Live Cells

Cooperation between the chemistry and pharmacy and medicine departments
Coordinator: Prof. Dr. Andriy Mokhir
Project partner: Profs. Schatz, Tsogoeva, Jux, Heinrich, Beierlein, Clark, Guldi, Prante

Project

An interdisciplinary team from the fields of organic chemistry (Mokhir, Schatz, Tsogoeva, Jux), pharmaceutical chemistry (Heinrich), physical chemistry (Guldi), theoretical chemistry (Beierlein, Clark) and medicine (Prante) has been working on the development since 01.01.2017 of chemical reactions (CO, CS, C-Se, CC) compatible with living cells. These reactions are said to lead to the creation of either new drugs or easily detectable (e.g. fluorescent or radioactive) components. The results obtained are important for the development of new therapies for diseases such as cancer or chronic inflammation as well as for new diagnostic instruments.

Additional Information

Singlet fission in novel organic materials - an approach towards highly-efficient solar cells

Cooperation between the chemistry and pharmacy and physics departments
Coordinator: Prof. Dr. Thomas Fauster
Project partner: Profs. Guldi, Tykwinski

Project

One strategy to improve the efficiency of solar cells is to generate two excited electrons from just one photon. This singlet splitting process is the conversion of a singlet exciton into two triplet excitons. In coordinated, close cooperation between synthetic and physical chemistry, surface and molecular physics as well as theoretical physics, the fundamental processes of singlet fission should be elucidated. The understanding gained leads to knowledge-based design and manufacture of molecules for a future generation of highly efficient solar cells based on environmentally friendly and inexpensive materials.

Additional Information

Neurotrition

Cooperation: Faculty of Science and Medicine
Coordinator: Prof. Dr. Monika Pischetsrieder

Project

Neurotrition describes the interaction between nutrition and brain function (neurofunction). Food components and forms of food can modulate brain functionality and activity, while on the other hand the activity pattern in the brain influences the quality and quantity of food intake. In both cases, however, it is unclear how. The Neurotrition project therefore aims to bundle FAU's scientific, medical and medical technology know-how in order to systematically examine neurotrition on several functional levels. The aim is to find out how, on the one hand, our brain functionality is influenced by nutritional substances and, on the other hand, how neurophysiological processes influence the amount and selection of food consumed.

Additional Information

Medicinal Chemistry: Redox-Active Small Inorganic Molecules as Biological Mediators and Therapeutic Drugs

Cooperation: Faculty of Medicine and Science
Coordinator: Prof. Dr. Ivana Ivanovíc-Burmazovíc
Participants: Ivanovíc-Burmazovíc, Burzlaff, Fink

Project

Chronic inflammation, pain, and signs of aging are important factors in many autoimmune and infectious diseases. Modern cytokine inhibitors (“biologicals”) have improved the treatment of inflammation in autoimmune diseases, but they also have significant disadvantages. They are very expensive, have been associated with infectious complications, and become less effective due to neutralizing antibodies. As part of the research project, new inorganic compounds for the therapeutic treatment of inflammation are therefore to be developed. Inexpensive, inorganic bioactive metal- and sulfur-based small molecules are promising new approaches for the treatment of chronic inflammatory diseases in an aging population.

Additional Information

TOPbiomat: Tissue / Organ Engineering with self-assembling proteins and bioactive biomaterials: A new therapeutic approach for regenerative medicine

Cooperation between technical, scientific and medical faculties
Coordinator: Prof. Dr. Aldo R. Boccaccini
Project partner: Prof. Clark

Project

The aim of the overall project is the fundamental research and development of cell-based organ structures and a complete regeneration of damaged organs based on them, e.g. bones with integrated vessels. Based on the combination of new manufacturing processes for three-dimensional framework structures with bioactive materials, specific growth factors and the patient's own cells, the micro-anatomical structure of bones and blood vessels is to be simulated. In the future, new intelligent therapies should be possible through the use of tailor-made biomaterials and the production of complete organs or organ components in the laboratory or directly in the operating room on or in the patient. This combination eliminates the complicated and tedious cultivation of the organs.

Additional Information

Next generation solar power

Non-material support through the Emerging Fields Initiative

Cooperation between the natural sciences and technical faculties
Coordinator: Prof. Dr. Dirk Guldi
Project partner: Prof. Guldi

Project

The steadily growing demand for energy has led to a significant increase in the research and development of alternative, non-fossil fuels. The research project “Next generation solar power” aims to develop a groundbreaking platform to produce chemical fuels using solar energy. The new center relies on future generations of photovoltaics, the nanotubular metal oxide architecture (NMOA) for solar water splitting and artificial leaves (AL). Ultimately, the aim is to produce fuels and electricity with the highest efficiency and maximum ecological sustainability, the energy costs of which are comparable to those of current energy generation from fossil fuels.


Fission is only observed with nuclides that are sufficiently heavy, from thorium-232 upwards. Only with them is the decomposition into lighter nuclei easy and possible with the release of binding energy. The splitting according to the droplet model can be clearly understood through oscillation and tearing of the core: The animated large view of the above picture shows how the core (red) is hit by a neutron (blue), elongates and constricts in the middle. The long range of the mutual electrical repulsion of the protons then outweighs the attractive nuclear force (see atomic nucleus) with its short range and drives the two ends apart, so that the nucleus disintegrates into two or three fragments - highly excited, medium-weight nuclei. By changing the binding energy, the total mass decreases accordingly (mass defect). Except for the fragment cores (Fissure fragments) usually a few single neutrons are released, typically two or, as in the picture, three.

The energy spectrum of these neutrons has the form of a Maxwell distribution, so it is continuous and extends up to about 15 MeV. The absolute temperature, which is decisive in the Boltzmann statistics, has hardly any physical significance here, but is treated as a free parameter in order to adapt the curve to the measured shape of the spectrum. The mean neutron energy is around 2 MeV. It depends somewhat on the split [1] nuclide and in the case of neutron-induced splitting (see below) also on the energy of the splitting neutron. Because of the asymmetry of the Maxwell distribution curve, the mean energy is different from the most probable energy; the maximum of the curve is around 0.7 MeV. [2]

About 99% of the neutrons are emitted as prompt neutrons directly during the fission within about 10-14 seconds. The rest, the delayed neutrons, are released from the fission fragments milliseconds to minutes later.

Some types of atomic nuclei (nuclides) split without any external influence. This spontaneous fission is a type of radioactive decay. In terms of quantum mechanics, it can be explained by the tunnel effect, similar to alpha decay.

Spontaneous fission finds practical application as a source of free neutrons. For this purpose, the Californium isotope 252 C f < displaystyle ^ <252> mathrm > used.

The neutron-induced fission, a nuclear reaction, is of great technical importance. A free neutron comes so close to an atomic nucleus that it can be absorbed by it. The nucleus gains the binding energy and possible kinetic energy of this neutron, is in an excited state and splits. Instead of fission, other processes are also possible, for example neutron capture. The excited atomic nucleus is excited by the emission of one or more gamma quanta and changes to its ground state.

The neutron-induced fission is fundamentally - with a smaller or larger effective cross-section - in all elements with ordinal numbers Z possible from 90 (thorium) and has been observed for many of its isotopes. [3]

Because of its importance for civil energy generation and for nuclear weapons, the neutron-induced fission is mainly treated in the following.

The total number of protons and neutrons is retained with every nuclear fission. By far the most common case is splitting into just two new nuclei (Fissure fragments) only in a few parts per thousand of all splits does a third fragment arise (ternary Cleavage) with mostly very small mass numbers up to a maximum of about 30. [4]

With two fission fragments, many different nuclide pairs are possible. Usually a lighter (mass number around 90) and a heavier fissure fragment (mass number around 140) arise. The frequency distribution (the yield plotted as a function of the mass number of the fission fragment) therefore has two maxima.

As an example, two ways of splitting plutonium-239 after absorption of a neutron (n) are mentioned:

94 239 P u + 0 1 n → 56 144 B a + 38 94 S r + 2 0 1 n < displaystyle <> _ < 94> ^ <239> mathrm + <> _ <0> ^ <1> mathrm to <> _ < 56> ^ <144> mathrm + <> _ <38> ^ <94> mathrm +2 <> _ <0> ^ <1> mathrm > 94 239 P u + 0 1 n → 51 130 S b + 43 107 T c + 3 0 1 n < displaystyle <> _ < 94> ^ <239> mathrm + <> _ <0> ^ <1> mathrm to <> _ < 51> ^ <130> mathrm + <> _ < 43> ^ <107> mathrm +3 <> _ <0> ^ <1> mathrm >

The fission fragments are medium-weight nuclides with a relatively high proportion of neutrons. They took over this surplus of neutrons from the original nucleus. They are therefore unstable and in some cases initially emit additional neutrons. These delayed neutrons can also trigger further nuclear fission; they are important for the controllability of nuclear reactors.

The fission products, which are still unstable afterwards, continue to reduce their surplus of neutrons through successive beta-minus decays. Since the mass number of the atomic nucleus remains unchanged during beta decay, the nuclides that arise one after the other from a given fission fragment nucleus form an isobaric chain - they are atomic nuclei of different chemical elements, but with the same mass number. This chain of transformation ends when a stable nuclide has formed. The half-lives are short at the beginning of the chain, but can be many years for the final decays. Exact numerical values ​​for the frequency of the different isobar chains, depending on the split nuclide and the energy of the splitting neutron, can be found in the literature. [5]

Energy release

The two fission products together have a higher mass defect than the heavy starting core. Because of the equivalence of mass and energy, this difference in mass defects is released as energy. In the following explanation, for the sake of simplicity, it is assumed that a 235 U nucleus takes up a neutron and then breaks up into two equal fragments with a mass number of 118 (in the case of nuclear fission actually occurring, the nuclei that are formed usually have different weights, and a few individual neutrons remain). Average values ​​of the binding energy per nucleon from the graphic are used for the calculation. The energy is given in the unit megaelectron volt (MeV).

  • To simplify matters, 235 individual nucleons (92 protons and 143 neutrons) and the captured neutron are initially calculated one Core composed. This would result in 236 × 7, 7 MeV = 1817 MeV < displaystyle 236 times 7 <,> 7 < text> = 1817 < text>> Energy to be released. Conversely, in order to completely split a U-236 nucleus into its nucleons, this amount of energy is necessary.
  • Will a Put together a fragment, one would get 118 × 8, 6 MeV = 1015 MeV < displaystyle 118 times 8 <,> 6 < text> = 1015 < text>> .
  • When a uranium-235 core is split into two equal parts, the energy difference (2 × 1015) MeV - 1817 MeV = 213 MeV < displaystyle left (2 times 1015 right) < text> -1817 < text> = 213 < text>> become free.
  • This energy is given off by the fact that both fragments and the released neutrons fly apart at a very high speed. The fragments in the surrounding material are slowed down and generate "frictional heat", more precisely: they transfer their kinetic energy in individual collisions to many atoms of the surrounding material, one after the other, until they are slowed down to the speed that corresponds to the material temperature.

Energy balance

The energy of around 200 MeV released during nuclear fission is distributed among the particles and radiation generated during nuclear fission. The table shows the energy values ​​of a typical fission process. [6] Most of this energy can be used in a nuclear reactor, only the energy of the escaping antineutrinos and part of the gamma radiation is not converted into heat.

Type of energy / type of radiation Average energy
Kinetic energy of the fissure fragments 167 MeV
Prompt gamma radiation 6 MeV
kinetic energy of neutrons 5 MeV
Electrons from fission fragment beta decay 8 MeV
Gamma radiation from fissure fragments 6 MeV
Electron antineutrinos from fission fragment beta decay 12 MeV
Total energy per split 204 MeV

Thermal neutrons

By thermal neutrons - d. H. those with relatively low kinetic energy - are mostly only isotopes with an odd number of neutrons that can be easily split. Only these atomic nuclei gain by absorbing a neutron Couple energy added. “Easily cleavable” means that the effective cross-section of the nucleus for cleavage by a thermal neutron is hundreds to thousands of barns. “Poorly fissile” means that this effective cross-section is only of the order of 1 barn or smaller.

Americium, as element 95, has an even number of neutrons with its odd number of protons for odd numbers of nucleons, while plutonium, as the 94th element, with its even number of protons for odd numbers of nucleons also has odd numbers of neutrons. Therefore americium 241 Am is difficult to split with thermal neutrons (3.1 barn), in contrast to plutonium 241 Pu (1010 barn).

Fast neutrons

The neutrons released during the fission have kinetic energies in the MeV range. With such fast neutrons, nuclides with an even number of neutrons can also be split, the pair energy then hardly has any effect on the cross-section. However, the cross sections for the “fast fission” do not reach the high values ​​of some “thermal” fission.

With some fissile materials, the rapid fission leads to a particularly high yield of new neutrons per fissioned core. This is exploited in breeder reactors.

In the three-stage bomb, very fast neutrons with more than 14 MeV are generated by nuclear fusion of hydrogen isotopes. These split uranium-238 cores in the bomb shell consisting of depleted uranium. The explosive power of the bomb and also the fallout are thereby greatly increased.

The smallest mass of a fissile material in which a chain reaction can be sustained is called the critical mass. It depends on the presence and amount of a moderator substance and on the geometric arrangement. A thin sheet of metal would lose almost all neutrons to the outside, while neutrons within a compact object are more likely to hit other atomic nuclei. The smallest critical mass is achieved with a spherical arrangement. This can be reduced by compressing the material, there is no absolute lower limit. The geometric dependency of the critical mass is used to avoid the criticality leading to a chain reaction when manufacturing or processing nuclear fuels. For example, chemical reactions are carried out in shallow tubs in which the material is distributed over large areas.

Nuclear reactors

The neutron-induced fission as a chain reaction in nuclear reactors is of economic importance. Mainly the nuclides uranium-235 and plutonium-239 are used. Nuclear reactors based on thorium-232 and uranium-233 were also planned or tested.

The energy released by nuclear fission is around 200 MeV per atomic nucleus, many times higher than in chemical reactions (typically around 20 eV per molecule). The energy occurs mainly as the kinetic energy of the fission fragments, to a lesser extent also in the radiation from their radioactive decay. The delayed neutrons, which are crucial for the controllability of nuclear reactors, are also released from the fission fragments after the actual fission reaction.

In reactors, the kinetic energy of the fission products and the energy of the radiation generated are converted into heat through collisions with the surrounding material. Only the resulting electron antineutrinos, part of the gamma radiation and part of the free neutrons escape from the reaction zone, the reactor core.

Nuclear weapons

the exponentially The growing nuclear fission chain reaction of a promptly supercritical arrangement of fissile materials serves as an energy source for "normal" nuclear weapons. The “destructive energy” is released primarily as light radiation, heat and radioactivity and secondarily in the form of a pressure wave. In the case of hydrogen bombs, a nuclear fission serves as a detonator for a nuclear fusion, i.e. the fusion of light atomic nuclei.

The collision of a high-energy gamma quantum (in the MeV energy range) can lead to the splitting of a heavy nucleus (Photocleavage). [7] This is to be distinguished from the nuclear photo effect, in which only a neutron, a proton or an alpha particle is released from the nucleus, but the nucleus is not split.

The collision of a charged particle can also lead to nuclear fission if it transfers sufficient energy to the nucleus. For example, proton and muon-induced fission processes have been observed. [8th]

Even a compound core with a very large nuclear spin, such as can arise in heavy ion reactions, can reduce its excitation energy by splitting.

These splitting processes do not have any technical applications.

It has been known since the work of Ernest Rutherford that atomic nuclei can be changed by bombarding them with fast particles. With the discovery of the neutron by James Chadwick in 1932, it became clear that there had to be many ways in which atomic nuclei could be transformed. Among other things, attempts were made to produce new, even heavier nuclides by introducing neutrons into heavy nuclei.

According to the assumptions of Enrico Fermi, [9] who already saw fission products of uranium in Rome, but misinterpreted them, represented inter alia. Ida Noddack-Tacke [10] the correct assumption of the splitting of the newly formed nucleus. [11] However, in 1934 these speculative assumptions were still considered dubious, and no physicist checked them experimentally, not even Ida Noddack herself. Otto Hahn and his assistant Fritz Straßmann then succeeded on December 17, 1938 at the Berlin Kaiser Wilhelm Institute for Chemistry with the proof of a neutron-induced nuclear fission of uranium through the radiochemical detection of the fission product barium. They published their discovery on January 6, 1939 in the journal "Die Naturwissenschaften". [12] By this time Lise Meitner had already been in Sweden for a few months, where she had emigrated with Hahn's help, as she had to flee Nazi Germany as a Jew. Together with her nephew Otto Frisch, who also emigrated, she was able to publish a first physical interpretation of the splitting process in the English "Nature" on February 10, 1939, as Hahn was the first to inform her by letter about the radiochemical results. Otto Hahn and Fritz Straßmann are therefore considered to be the discoverers of nuclear fission, and Lise Meitner and Otto Frisch are the first to publish a correct theoretical explanation of the process. The expression also comes from Frisch nuclear fission, so "nuclear fission", which was then adopted internationally, while Hahn originally used the term "uranium fission".

On January 16, 1939, Niels Bohr traveled to the USA to discuss physical problems with Albert Einstein for a few months. Shortly before he left Denmark, Frisch and Meitner told him about their interpretation of Hahn-Straßmann's test results. After his arrival in the USA, Bohr shared this with his former student John Archibald Wheeler and other interested parties. It was through them that the news spread to other physicists, including Enrico Fermi of Columbia University. Fermi recognized the possibility of a controlled fission chain reaction and carried out the first successful reactor experiment in the Chicago Pile with his team in Chicago in 1942.


Discovery story

The possibility of spontaneous fission of uranium was first suggested in 1939 by Niels Bohr and John Archibald Wheeler. & # 913 & # 93

A year later, Georgi Fljorow and Konstantin Petrschak succeeded in demonstrating this phenomenon on natural uranium. & # 914 & # 93 To do this, they used the ionization chamber method developed by Otto Frisch (see the discovery of nuclear fission). However, they had to increase the chamber volume considerably in order to accommodate a sample amount of approx. 15 g uranium oxide U3O8 to accommodate in it. With this sample the apparatus registered about six impulses per hour. The ionization chamber was empty (i.e. without U3O8-Filling), not a single pulse was measured in five hours. On the basis of this measurement and numerous control experiments, the authors came to the conclusion that the observed impulses only from very high-energy, from the U3O8-Surface emitted fragments of uranium could originate. Since the involvement of neutrons could be ruled out, the test results could only be explained by the assumption of spontaneous fission.

However, the experiment did not provide any information about which of the three natural uranium isotopes, 238 U, 235 U and / or 234 U, had spontaneously split. Today, the non-zero partial decay probabilities for spontaneous fission of all three isotopes are known. That of 238 U is the largest.


Occurrence

Prothrombin is factor II in blood clotting. It is created in the liver and is continuously released into the blood. Prothrombin can be detected in the blood plasma. There are only small traces of free thrombin in the blood, which is normally only formed on site from the prothrombin when tissue is damaged. Thrombinemia, the occurrence of free thrombin and thus the coagulation of blood in uninjured vessels, is prevented by the body's own antithrombin.


Nuclear fission

At a Nuclear fission an atomic nucleus is divided into two fragments of comparable mass. Nuclear fission can occur by itself in heavy nuclei (spontaneous split) or forced by supplying suitable excitation energy (induced cleavage).

The masses of the two Fission products behave like 2: 3. When splitting, about 10% of the Nuclear binding energy, about 120-200 MeV, as kinetic energy of the fragments. In addition, the fission process with the emission of intense gamma radiation and two to three fast neutrons (Fission neutrons) tied together. Some of the fission neutrons only appear after a few seconds (delayed neutrons). Das bietet die Möglichkeit, den Neutronenfluss zu steuern und so gezielt Kettenreaktionen auszulösen. Deswegen lässt sich die K. zur Gewinnung von Kernenergie in Kernreaktoren oder zum Auslösen einer unkontrollierten Explosion in Kernwaffen ausnutzen.

One induzierte Spaltung kann außer durch Absorption eines Neutrons auch durch Absorption eines energiereichen Protons, Deuterons oder anderen energiereichen Teilchens oder auch eines Gammaquants (Fotospaltung) herbeigeführt werden. Die Spaltprodukte sind meist radioaktiv, da sie i. A. einen erheblichen Neutronenüberschuss besitzen, den sie durch mehrfachen Betazerfall ausgleichen.

Das Uranisotop 235 U wird durch langsame Neutronen gespalten 238 U hingegen ist nur durch Neutronen mit Energien von über 1 MeV spaltbar und wandelt sich bei Anlagerung eines langsameren Neutrons in 239 U um. Dieses geht nach Emission zweier schneller Elektronen in das Plutoniumisotop 239 Pu über, das seinerseits wieder durch langsame Neutronen gespalten werden kann. Daher dienen v. a. 235 U und 239 Pu als Spaltmaterial in Kernreaktoren bzw. in Kernwaffen. Bei der Spaltung von 1 g 235 U wird die Energie (2,26 cdot 10^4, ext) frei dies entspricht der Sprengkraft von 20 t des chemischen Sprengstoffs TNT (Trinitrotoluol).


Kernspaltung

Kernspaltung bezeichnet einen Prozess der Kernphysik, bei dem ein Atomkern unter Energiefreisetzung in zwei oder mehr Bestandteile zerlegt wird. Seltener wird die Kernspaltung auch als Kernfission (v. lat. fissio = das Spalten) bezeichnet - ein Begriff, der nicht mit Kernfusion, dem Verschmelzen zweier Atomkerne, verwechselt werden darf.

Further recommended specialist knowledge

Daily visual inspection of the laboratory balances

Erkennen Sie die Auswirkungen elektrostatischer Aufladungen auf Ihre Waage

Richtiges Wägen mit Laborwaagen: Die Wägefibel



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