Monthly Archives: October 2018

Frank Morgan (matematico)

«La matematica si divide in due grandi filoni, e cioè la matematica pura e la matematica applicata. La matematica applicata studia e tenta di risolvere i problemi; la matematica pura studia argomenti dei quali non si sa ancora se, e quando, diventeranno problemi.»

Frank Morgan (…) è un matematico statunitense, specializzato in teoria geometrica della misura negli spazi euclidei, in geometria differenziale e nello studio delle superfici minime.

È noto soprattutto per aver dimostrato la congettura della doppia bolla standard, che dice che la doppia bolla di sapone è il sistema più efficiente per racchiudere e separare due volumi dati nello spazio euclideo (dove efficiente sta a significare che le bolle racchiudono il maggiore volume possibile nella minore superficie possibile).

È celebre anche per un aneddoto matematico[senza fonte], volutamente formulato in maniera da risultare paradossale:

«Tre tizi entrano in un albergo, ciascuno con 10 dollari in tasca. Prendono una stanza a 30 dollari per notte. Poco dopo un fax della direzione comunica che il prezzo della camera è ridotto a 25 dollari a notte. L’addetto al ricevimento dà al fattorino 5 dollari da restituire ai tre che dividono la stanza. Non avendo mai ricevuto da loro una mancia e non sapendo come dividere 5 dollari in tre, il fattorino decide di intascare 2 dollari e restituire ai tre un dollaro a testa. Così ognuno dei tre clienti ora ha speso 9 dollari e il fattorino ne ha 2, per un totale di 29 dollari. Dov’è finito il dollaro che manca?»

Thermite

Thermite (/ˈθɜːrmaɪt/) is a pyrotechnic composition of metal powder, which serves as fuel, and metal oxide. When ignited by heat, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brief bursts of heat and high temperature in a small area. Its form of action is similar to that of other fuel-oxidizer mixtures, such as black powder.

Thermites have diverse compositions. Fuels include aluminium, magnesium, titanium, zinc, silicon, and boron. Aluminium is common because of its high boiling point and low cost. Oxidizers include bismuth(III) oxide, boron(III) oxide, silicon(IV) oxide, chromium(III) oxide, manganese(IV) oxide, iron(III) oxide, iron(II,III) oxide, copper(II) oxide, and lead(II,IV) oxide.

The reaction, also called the Goldschmidt process, is used for thermite welding, often used to join rail tracks. Thermites have also been used in metal refining, disabling munitions, and in incendiary weapons. Some thermite-like mixtures are used as pyrotechnic initiators in fireworks.

In the following example, elemental aluminium reduces the oxide of another metal, in this common example iron oxide, because aluminium forms stronger and more stable bonds with oxygen than iron:

The products are aluminium oxide, elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation.

Other metal oxides can be used, such as chromium oxide, to generate the given metal in its elemental form. For example, a copper thermite reaction using copper oxide and elemental aluminium can be used for creating electric joints in a process called cadwelding, that produces elemental copper (it may react violently):

Thermites with nanosized particles are described by a variety of terms, such as metastable intermolecular composites, super-thermite, nano-thermite, and nanocomposite energetic materials.

The thermite (thermit) reaction was discovered in 1893 and patented in 1895 by German chemist Hans Goldschmidt. Consequently, the reaction is sometimes called the “Goldschmidt reaction” or “Goldschmidt process”. Goldschmidt was originally interested in producing very pure metals by avoiding the use of carbon in smelting, but he soon discovered the value of thermite in welding.

The first commercial application of thermite was the welding of tram tracks in Essen in 1899.

Red iron(III) oxide (Fe2O3, commonly known as rust) is the most common iron oxide used in thermite. Magnetite also works. Other oxides are occasionally used, such as MnO2 in manganese thermite, Cr2O3 in chromium thermite, quartz in silicon thermite, or copper(II) oxide in copper thermite, but only for specialized purposes. All of these examples use aluminium as the reactive metal. Fluoropolymers can be used in special formulations, Teflon with magnesium or aluminium being a relatively common example. Magnesium/teflon/viton is another pyrolant of this type.

Combinations of dry ice (frozen carbon dioxide) and reducing agents such as magnesium, aluminium and boron follow the same chemical reaction as with traditional thermite mixtures, producing metal oxides and carbon. Despite the very cold temperature of a dry ice thermite mixture, such a system is capable of being ignited with a flame. When the ingredients are finely divided, confined in a pipe and armed like a traditional explosive, this cryo-thermite is detonatable and a portion of the carbon liberated in the reaction emerges in the form of diamond.

In principle, any reactive metal could be used instead of aluminium. This is rarely done, because the properties of aluminium are nearly ideal for this reaction:

Although the reactants are stable at room temperature, they burn with an extremely intense exothermic reaction when they are heated to ignition temperature. The products emerge as liquids due to the high temperatures reached (up to 2500 °C with iron(III) oxide)—although the actual temperature reached depends on how quickly heat can escape to the surrounding environment. Thermite contains its own supply of oxygen and does not require any external source of air. Consequently, it cannot be smothered, and may ignite in any environment given sufficient initial heat. It burns well while wet, and cannot be easily extinguished with water—though enough water to remove sufficient heat may stop the reaction. Small amounts of water boil before reaching the reaction. Even so, thermite is used for welding underwater.

The thermites are characterized by almost complete absence of gas production during burning, high reaction temperature, and production of molten slag. The fuel should have high heat of combustion and produce oxides with low melting point and high boiling point. The oxidizer should contain at least 25% oxygen, have high density, low heat of formation, and produce metal with low melting and high boiling point (so the energy released is not consumed in evaporation of reaction products). Organic binders can be added to the composition to improve its mechanical properties, however they tend to produce endothermic decomposition products, causing some loss of reaction heat and production of gases.

The temperature achieved during the reaction determines the outcome. In an ideal case, the reaction produces a well-separated melt of metal and slag. For this, the temperature must be high enough to melt both reaction products, the resulting metal and the fuel oxide. Too low a temperature produces a mixture of sintered metal and slag; too high a temperature (above the boiling point of any reactant or product) leads to rapid production of gas, dispersing the burning reaction mixture, sometimes with effects similar to a low-yield explosion. In compositions intended for production of metal by aluminothermic reaction, these effects can be counteracted. Too low a reaction temperature (e.g., when producing silicon from sand) can be boosted with addition of a suitable oxidizer (e.g., sulfur in aluminium-sulfur-sand compositions); too high a temperature can be reduced by using a suitable coolant and/or slag flux. The flux often used in amateur compositions is calcium fluoride, as it reacts only minimally, has relatively low melting point, low melt viscosity at high temperatures (therefore increasing fluidity of the slag) and forms a eutectic with alumina. Too much of flux however dilutes the reactants to the point of not being able to sustain combustion. The type of metal oxide also has dramatic influence to the amount of energy produced; the higher the oxide, the higher the amount of energy produced. A good example is the difference between manganese(IV) oxide and manganese(II) oxide, where the former produces too high temperature and the latter is barely able to sustain combustion; to achieve good results a mixture with proper ratio of both oxides should be used.

The reaction rate can be also tuned with particle sizes; coarser particles burn slower than finer particles. The effect is more pronounced with the particles requiring being heated to higher temperature to start reacting. This effect is pushed to the extreme with nano-thermites.

The temperature achieved in the reaction in adiabatic conditions, when no heat is lost to the environment, can be estimated using the Hess’s law – by calculating the energy produced by the reaction itself (subtracting the enthalpy of the reactants from the enthalpy of the products) and subtracting the energy consumed to heating the products (from their specific heat, when the materials only change their temperature, and their enthalpy of fusion and eventually enthalpy of vaporization, when the materials melt or boil). In real conditions, the reaction loses heat to the environment, the achieved temperature is therefore somewhat lower. The heat transfer rate is finite, so the faster the reaction is, the closer to adiabatic condition it runs and the higher is the achieved temperature.

The most common composition is the iron thermite. The oxidizer used is usually either iron(III) oxide or iron(II,III) oxide. The former produces more heat. The latter is easier to ignite, likely due to the crystal structure of the oxide. Addition of copper or manganese oxides can significantly improve the ease of ignition.

The original mixture, as invented, used iron oxide in the form of mill scale. The composition was very difficult to ignite.

Copper thermite can be prepared using either copper(I) oxide (Cu2O, red) or copper(II) oxide (CuO, black). The burn rate tends to be very fast and the melting point of copper is relatively low so the reaction produces a significant amount of molten copper in a very short time. Copper(II) thermite reactions can be so fast that copper thermite can be considered a type of flash powder. An explosion can occur and send a spray of copper drops to considerable distance.

Copper(I) thermite has industrial uses in e.g., welding of thick copper conductors (“cadwelding”). This kind of welding is being evaluated also for cable splicing on the US Navy fleet, for use in high-current systems, e.g., electric propulsion.

Thermate composition is a thermite one enriched with a salt-based oxidizer (usually nitrates, e.g., barium nitrate, or peroxides). In contrast with thermites, thermates burn with evolution of flame and gases. The presence of the oxidizer makes the mixture easier to ignite and improves penetration of target by the burning composition, as the evolved gas is projecting the molten slag and providing mechanical agitation. This mechanism makes thermate more suitable than thermite for incendiary purposes and for emergency destruction of sensitive equipment (e.g., cryptographic devices), as thermite’s effect is more localized.

Metals can burn under the right conditions, similar to the combustion process of wood or gasoline. In fact, rust is the result of oxidation of steel or iron at very slow rates. A thermite reaction is a process in which the correct mixture of metallic fuels combine and ignite. Ignition itself requires extremely high temperatures.

Ignition of a thermite reaction normally requires a sparkler or easily obtainable magnesium ribbon, but may require persistent efforts, as ignition can be unreliable and unpredictable. These temperatures cannot be reached with conventional black powder fuses, nitrocellulose rods, detonators, pyrotechnic initiators, or other common igniting substances. Even when the thermite is hot enough to glow bright red, it doesn’t ignite, as it must be at or near white-hot to initiate the reaction.[citation needed] It is possible to start the reaction using a propane torch if done correctly.

Often, strips of magnesium metal are used as fuses. Because metals burn without releasing cooling gases, they can potentially burn at extremely high temperatures. Reactive metals such as magnesium can easily reach temperatures sufficiently high for thermite ignition. Magnesium ignition remains popular among amateur thermite users, mainly because it can be easily obtained.

The reaction between potassium permanganate and glycerol or ethylene glycol is used as an alternative to the magnesium method. When these two substances mix, a spontaneous reaction begins, slowly increasing the temperature of the mixture until it produces flames. The heat released by the oxidation of glycerine is sufficient to initiate a thermite reaction.

Apart from magnesium ignition, some amateurs also choose to use sparklers to ignite the thermite mixture. These reach the necessary temperatures and provide enough time before the burning point reaches the sample. This can be a dangerous method, as the iron sparks, like the magnesium strips, burn at thousands of degrees and can ignite the thermite even though the sparkler itself is not in contact with it. This is especially dangerous with finely powdered thermite.

Similarly, finely powdered thermite can be ignited by a flint spark lighter, as the sparks are burning metal (in this case, the highly reactive rare-earth metals lanthanum and cerium). Therefore, it is unsafe to strike a lighter close to thermite.

Thermite reactions have many uses. Thermite is not an explosive; instead it operates by exposing a very small area to extremely high temperatures. Intense heat focused on a small spot can be used to cut through metal or weld metal components together both by melting metal from the components, and by injecting molten metal from the thermite reaction itself.

Thermite may be used for repair by the welding in-place of thick steel sections such as locomotive axle-frames where the repair can take place without removing the part from its installed location.

Thermite can be used for quickly cutting or welding steel such as rail tracks, without requiring complex or heavy equipment. However, defects such as slag inclusions and voids (holes) are often present in such welded junctions and great care is needed to operate the process successfully. The numerical analysis of thermite welding of rails has been approached similar to casting cooling analysis. Both this finite element analysis and experimental analysis of thermite rail welds has shown that weld gap is the most influential parameter affecting defect formation. Increasing weld gap has been shown to reduce shrinkage cavity formation and cold lap welding defects, and increasing preheat and thermite temperature further reduces these defects. However, reducing these defects promotes a second form of defect: microporosity. Care must also be taken to ensure that the rails remain straight, without resulting in dipped joints, which can cause wear on high speed and heavy axle load lines.

A thermite reaction, when used to purify the ores of some metals, is called the thermite process, or aluminothermic reaction. An adaptation of the reaction, used to obtain pure uranium, was developed as part of the Manhattan Project at Ames Laboratory under the direction of Frank Spedding. It is sometimes called the Ames process.

Copper thermite is used for welding together thick copper wires for the purpose of electrical connections. It is used extensively by the electrical utilities and telecommunications industries (exothermic welded connections).

Thermite hand grenades and charges are typically used by armed forces in both an anti-materiel role and in the partial destruction of equipment; the latter being common when time is not available for safer or more thorough methods. For example, thermite can be used for the emergency destruction of cryptographic equipment when there is a danger that it might be captured by enemy troops. Because standard iron-thermite is difficult to ignite, burns with practically no flame and has a small radius of action, standard thermite is rarely used on its own as an incendiary composition. In general, an increases in the volume of gaseous reaction products of a thermite blend increases the heat transfer rate (and therefore damage) of that particular thermite blend. It is more usually used with other ingredients that increase its incendiary effects. Thermate-TH3 is a mixture of thermite and pyrotechnic additives that have been found superior to standard thermite for incendiary purposes. Its composition by weight is generally about 68.7% thermite, 29.0% barium nitrate, 2.0% sulfur, and 0.3% of a binder (such as PBAN). The addition of barium nitrate to thermite increases its thermal effect, produces a larger flame, and significantly reduces the ignition temperature. Although the primary purpose of Thermate-TH3 by the armed forces is as an incendiary anti-materiel weapon, it also has uses in welding together metal components.

A classic military use for thermite is disabling artillery pieces, and it has been used for this purpose since World War II, such as at Pointe du Hoc, Normandy. Thermite can permanently disable artillery pieces without the use of explosive charges, and therefore thermite can be used when silence is necessary to an operation. This can be done by inserting one or more armed thermite grenades into the breech and then quickly closing it; this welds the breech shut and makes loading the weapon impossible. Alternatively, a thermite grenade discharged inside the barrel of the gun fouls the barrel, making the weapon dangerous to fire. Thermite can also weld the traversing and elevation mechanism of the weapon, making it impossible to aim properly.[citation needed]

During World War II, both German and Allied incendiary bombs used thermite mixtures. Incendiary bombs usually consisted of dozens of thin thermite-filled canisters (bomblets) ignited by a magnesium fuse. Incendiary bombs created massive damage in many cities due to fires started by the thermite. Cities that primarily consisted of wooden buildings were especially susceptible. These incendiary bombs were utilized primarily during nighttime air raids. Bombsights could not be used at night, creating the need to use munitions that could destroy targets without the need for precision placement. In recent times, thermite was used by Russia (under Putin’s administration) in the Syrian Civil War. In mid 2016, Russian Television by mistake showed video of RBK-500 cluster bombs loaded with ZAB-2.5SM thermite incendiaries mounted on Su-34 bomber aircraft. In the video, the defense minister of Russia can be seen supervising the attacks on civilian areas.

Thermite usage is hazardous due to the extremely high temperatures produced and the extreme difficulty in smothering a reaction once initiated. Small streams of molten iron released in the reaction can travel considerable distances and may melt through metal containers, igniting their contents. Additionally, flammable metals with relatively low boiling points such as zinc (with a boiling point of 907 °C, which is about 1,370 °C below the temperature at which thermite burns) could potentially spray superheated boiling metal violently into the air if near a thermite reaction.[citation needed]

If, for some reason, thermite is contaminated with organics, hydrated oxides and other compounds able to produce gases upon heating or reaction with thermite components, the reaction products may be sprayed. Moreover, if the thermite mixture contains enough empty spaces with air and burns fast enough, the super-heated air also may cause the mixture to spray. For this reason it is preferable to use relatively crude powders, so the reaction rate is moderate and hot gases could escape the reaction zone.

Preheating of thermite before ignition can easily be done accidentally, for example by pouring a new pile of thermite over a hot, recently ignited pile of thermite slag. When ignited, preheated thermite can burn almost instantaneously, releasing light and heat energy at a much higher rate than normal and causing burns and eye damage at what would normally be a reasonably safe distance.[citation needed]

The thermite reaction can take place accidentally in industrial locations where workers use abrasive grinding and cutting wheels with ferrous metals. Using aluminium in this situation produces a mixture of oxides that can explode violently.

Mixing water with thermite or pouring water onto burning thermite can cause a steam explosion, spraying hot fragments in all directions.

Thermite’s main ingredients were also utilized for their individual qualities, specifically reflectivity and heat insulation, in a paint coating or dope for the German zeppelin Hindenburg, possibly contributing to its fiery destruction. This was a theory put forward by the former NASA scientist Addison Bain, and later tested in small scale by the scientific reality-TV show MythBusters with semi-inconclusive results (it was proven not to be the fault of the thermite reaction alone, but instead conjectured to be a combination of that and the burning of hydrogen gas that filled the body of the Hindenburg). The MythBusters program also tested the veracity of a video found on the Internet, whereby a quantity of thermite in a metal bucket was ignited while sitting atop several blocks of ice, causing a sudden explosion. They were able to confirm the results, finding huge chunks of ice as far as 50m from the point of explosion. Co-host Jamie Hyneman conjectured that this was due to the thermite mixture aerosolizing, perhaps in a cloud of steam, causing it to burn even faster. Hyneman also voiced skepticism about another theory explaining the phenomenon: that the reaction somehow separated the hydrogen and oxygen in the ice and then ignited them. This explanation claims that the explosion is due to the reaction of high temperature molten aluminium with water. Aluminium reacts violently with water or steam at high temperatures, releasing hydrogen and oxidizing in the process. The speed of that reaction and the ignition of the resulting hydrogen can easily account for the explosion verified. This process is akin to the explosive reaction caused by dropping metallic potassium into water.

Ministère fédéral de la Justice (Autriche)

Le ministère fédéral de la Justice (Bundesministerium für Justiz, BMJ) est le département ministériel chargé du droit, des juridictions et du ministère public au niveau fédéral en Autriche.

Il est dirigé depuis le par l’indépendant Josef Moser.

Le ministère fédéral de la Justice est compétent en matière de droit privé, principalement le droit civil, des affaires, d’auteur, des assurances et de la concurrence, de droit pénal, de droit des médias, de juridictions pénales et civiles, de ministère public, d’exécution des décisions de justice, d’emprisonnement, de faillites, et de réglementation des professions juridiques telles que les avocats et les notaires.

Le BMJ s’organise de la manière suivante :

Le premier ministère autrichien de la Justice naît en 1848, en même temps que la Cour suprême. Les deux sont en effet issus de l’Obersten Justizstelle, un organisme qui jouait à la fois le rôle d’une juridiction et édictait des lois judiciaires, à l’instar du Code civil autrichien de 1812.

Le ministère de la Justice est fusionné avec les ministères de l’Intérieur et de l’Enseignement au sein du « ministère d’État » en 1860, mais il est rétabli sept ans plus tard dans la partie autrichienne de l’empire d’Autriche-Hongrie. En 1918, l’office d’État pour la Justice apparaît en Autriche, désormais indépendante. Il se transforme en ministère fédéral de la Justice en 1920, à la suite de l’entrée en vigueur de la loi constitutionnelle fédérale. Dirigé de 1923 à 1927 par le vice-chancelier, le ministère est absorbé par celui du Reich à la Justice lorsque l’Autriche est annexée par l’Allemagne, en 1938.

Après la Seconde Guerre mondiale, un office d’État pour la Justice est établi en 1945. Il redevient peu de temps après le « ministère fédéral de la Justice » avec la remise en vigueur de la loi constitutionnelle fédérale.

Diploastrea heliopora

Diploastrea heliopora, commonly known as diploastrea brain coral or honeycomb coral among other vernacular names, is a species of hard coral in the family Diploastreidae. It is the only extant species in its genus. This species can form massive dome-shaped colonies of great size.

Diploastrea heliopora was first described in 1816 by the French naturalist Jean-Baptiste Lamarck as Astrea heliopora. It was transferred to the new genus Diploastrea by G. Matthai in 1914. Diploastrea heliopora was included in the family Agathiphylliidae by T.W. Vaughan and J.W. Wells in 1943. It was the only extant member of the family, which also included four fossil species. In 1956, Wells transferred the genus to Faviidae, and this has been widely accepted. However, recent molecular and phylogenetic studies show that this coral has certain unique features, and a separate family, Diploastreidae, has been reinstated. It is the only extant member of the family.

A colonial species, D. heliopora grows into domes 1 metre (3 ft 3 in) or more across. The corallites are plocoid (with an individual wall), round and closely packed, about 1 cm (0.4 in) in diameter and formed by extratentacular budding. The corallite walls are distinctive, being not solid but formed from the enlarged outer ends of the septa, which are not connected to each other. The columellae are large. The coral has a smooth surface and is usually cream or greyish-brown, sometimes tinged with green. It is a zooxanthellate species.

This species is widespread throughout the tropical waters of the Indo-West Pacific region, including the Red Sea, occurring at depths down to 30 m (100 ft). Its typical habitat is in silty environments without strong wave action such as protected fringing reefs and back reef slopes. In the atoll lagoons of the Indian Ocean it is often plentiful and dominant, while in the Red Sea it is uncommon.

Small gobies can often be found perching on this coral or swimming around the surface searching for food. This coral is a zooxanthellate species; the coral houses symbiotic dinoflagellates within its tissues which supply it with much of the nourishment it needs. The polyps supplement this by extending their tentacles to feed, but do so only at night.

D. heliopora is plentiful in some areas but less common elsewhere. In Indonesia it is collected for the aquarium trade, but apart from this, the threats it faces are those affecting coral reefs in general; climate change, ocean acidification, coral disease and human actions. The International Union for Conservation of Nature has assessed its conservation status as being “near threatened”.

Media related to Diploastrea heliopora at Wikimedia Commons

U 218

U 218 war ein deutsches Unterseeboot der Klasse VII D im Zweiten Weltkrieg. Es lief am 25. Januar 1942 vom Stapel und sank am 4. Dezember 1945.

U 218 war vom Typ VIID und somit ein schweres Minenlegerboot. Seine Höchstgeschwindigkeit lag bei 16,7 Knoten, was einer Geschwindigkeit von etwa 31 km/h entspricht. Es war 76,9 Meter lang und 6,4 Meter hoch und konnte bis zu 220 Meter tief tauchen. Es war ca. 1080 Tonnen schwer und hatte eine Besatzung von 4 Offizieren und bis zu 40 Mann. Insgesamt dienten 110 Männer an Bord von U 218.

Bereits 1940 von der Reichsregierung in Auftrag gegeben, wurde es erst am 5. Dezember 1941 fertiggestellt. Gebaut von der Germaniawerft in Kiel, lief es auch dort vom Stapel. Am 4. Dezember 1945 sank es im Zuge der britisch-polnischen “Operation Deadlight” im Schlepp des britischen Zerstörers HMS Southdowne 20 km vor der irischen Küste.

U 218 war während des Krieges zehn Mal auf Fahrt und versenkte zwei Handelsschiffe und ein Hilfskriegsschiff. Außerdem wurden ein Handelsschiff und ein Hilfskriegsschiff (Mine) beschädigt

U 218 verließ Kristiansand am 27. August 1942 in Richtung Nordatlantik. Es gehörte zur ‘Unterseebootgruppe Vorwärts’ unter Kapitänleutnant Richard Becker. Östlich von Neufundland beschädigte es am 11. September 1942 das norwegische Handelsschiff “Fjordaas”. Es musste die Unternehmung frühzeitig wegen Maschinenschäden beenden. Am 29. September 1942 lief es in Brest wieder ein. Somit dauerte die erste Unternehmung 33 Tage, und das Boot legte 5165 sm (9566 km) zurück.

Die zweite Fahrt, ebenfalls unter Kapitänleutnant Becker, dauerte 26 Tage (25. Oktober bis 21. November 1942). Dabei legte das Boot eine Strecke von 4083 sm (7562 km) zurück. Das Boot operierte zwischen Kap Vincent und Gibraltar. Ohne Schiffe zu beschädigen, musste es frühzeitig wegen Wasserbombenschäden die Rückfahrt antreten. Diesmal stand es unter den U-Boot-Gruppen Westwall und Natter.

Auch während der dritten Fahrt (7. Januar bis 10. März 1943) unter Kapitänleutnant Becker wurden keine Schiffe versenkt. Während der 61 Tage andauernden Operation fuhr es 16.481 km (8899 sm) westlich der Kanarischen Inseln und südlich der Azoren (U-Boot Gruppe Rochen).

Es wurden keine Schiffe beschädigt, aber ein U-Boot versorgt (U 459). Während der 43 Tage legte es 4380 sm (8112 km) zurück. Am 19. April 1943, einen Tag nach Beginn der Operation, musste U 218 wegen eines defekten Tiefenruders wieder Brest ansteuern. Danach legte es 15 Minen im Nordkanal und operierte anschließend im Nordatlantik (U-Boot Gruppen Naab, Mosel und Donau 2).

Die kürzeste Operation von U 218 dauerte nur neun Tage, vom 22. Juli 1943 bis 6. August 1943 mit einer Unterbrechung von sechs Tagen wegen Undichtigkeiten. In der Biskaya wurde es durch einen Fliegerangriff beschädigt und musste zurückkehren.

Am 19. September 1943 legte U 218 in Brest ab, um in den folgenden 79 Tagen 16.783 km auf See zurückzulegen. Die Operationsgebiete waren zuerst die Karibische See nordöstlich von Barbados, danach als Minenleger am Port of Spain und zuletzt an der St. Lucia-Passage südlich der Azoren. Auf dieser Fahrt wurde das britische Handelsschiff “Beatrice Beck” versenkt. Am 8. Dezember 1943 kam es in Brest wieder an.

Diese 85 Tage andauernde Fahrt begann am 12. Februar 1944 in Brest. Während der Operation legte das Boot 9595 sm (17.946 km) im Mittelatlantik zurück. Seine Route verlief über Brest, Azoren, Kleine Antillen, Barbados, St. Lucia, Martinique, Grenada, Port Castries, Trinidad und Puerto Rico, um dann 15 Minen vor San Juan zu legen. Ohne ein Schiff zu beschädigen, kehrte es am 7. Mai 1944 nach Brest zurück. Dort wurde U 218 anschließend mit einer Schnorchelanlage ausgestattet.

U 218 legte, nachdem es an der Invasionsfront, im Ärmelkanal und in der Biskaya operierte, 15 Minen vor Wolfs Rock, wodurch das britische Hilfskriegsschiff “HMS Empire Halberd” beschädigt wurde. Die Unternehmung dauerte 25 Tage und das Boot legte dabei 1101 sm (2039 km) zurück, diesmal jedoch zum größten Teil unter Wasser.

Während dieser 43 Tage dauernden Fahrt legte U 218 15 Minen vor Lizzard Head, nachdem es im westlichen Ärmelkanal operierte. Am 11. August 1944 musste es nach Brest zurück, da es durch ein britisches Schnellboot angegriffen wurde. Nach 2236 sm (4141 km) lief es in Bergen (Norwegen) ein. Es wurden keine Schiffe beschädigt. Dies war die erste Fahrt unter Kapitänleutnant Rupprecht Stock.

Zuvor wurde das Boot von Bergen nach Kristiansand verlegt. U 218 legte 14 Minen vor dem Firth of Clyde, wodurch auch das britische Handelsschiff “Ethel Crawford” versenkt wurde. Die Fahrt dauerte 47 Tage und das Boot operierte außerdem noch im Minch-Kanal, im Nordkanal und bei den Hebriden. Am 8. Mai 1945 erreichte es Bergen. Das war die letzte Fahrt der U 218.

U-Boote: U 1 | U 2 | U 3 | U 4 | U 5 | U 6 | U 7 | U 8 | U 9 | U 10 | U 11 | U 12 | U 13 | U 14 | U 15 | U 16 | U 17 | U 18 | U 19 | U 20 | U 21 | U 22 | U 23 | U 24 | U 25 | U 26 | U 27 | U 28 | U 29 | U 30 | U 31 | U 32 | U 33 | U 34 | U 35 | U 36 | U 37 | U 38 | U 39 | U 40 | U 41 | U 42 | U 43 | U 44 | U 45 | U 46 | U 47 | U 48 | U 49 | U 50 | U 51 | U 52 | U 53 | U 54 | U 55 | U 56 | U 57 | U 58 | U 59 | U 60 | U 61 | U 62 | U 63 | U 64 | U 65 | U 66 | U 67 | U 68 | U 69 | U 70 | U 71 | U 72 | U 73 | U 74 | U 75 | U 76 | U 77 | U 78 | U 79 | U 80 | U 81 | U 82 | U 83 | U 84 | U 85 | U 86 | U 87 | U 88 | U 89 | U 90 | U 91 | U 92 | U 93 | U 94 | U 95 | U 96 | U 97 | U 98 | U 99 | U 100 | U 101 | U 102 | U 103 | U 104 | U 105 | U 106 | U 107 | U 108 | U 109 | U 110 | U 111 | U 112 | U 113 | U 114 | U 115 | U 116 | U 117 | U 118 | U 119 | U 120 | U 121 | U 122 | U 123 | U 124 | U 125 | U 126 | U 127 | U 128 | U 129 | U 130 | U 131 | U 132 | U 133 | U 134 | U 135 | U 136 | U 137 | U 138 | U 139 | U 140 | U 141 | U 142 | U 143 | U 144 | U 145 | U 146 | U 147 | U 148 | U 149 | U 150 | U 151 | U 152 | U 153 | U 154 | U 155 | U 156 | U 157 | U 158 | U 159 | U 160 | U 161 | U 162 | U 163 | U 164 | U 165 | U 166 | U 167 | U 168 | U 169 | U 170 | U 171 | U 172 | U 173 | U 174 | U 175 | U 176 | U 177 | U 178 | U 179 | U 180 | U 181 | U 182 | U 183 | U 184 | U 185 | U 186 | U 187 | U 188 | U 189 | U 190 | U 191 | U 192 | U 193 | U 194 | U 195 | U 196 | U 197 | U 198 | U 199 | U 200 | U 201 | U 202 | U 203 | U 204 | U 205 | U 206 | U 207 | U 208 | U 209 | U 210 | U 211 | U 212 | U 213 | U 214 | U 215 | U 216 | U 217 | U 218 | U 219 | U 220 | U 221 | U 222 | U 223 | U 224 | U 225 | U 226 | U 227 | U 228 | U 229 | U 230 | U 231 | U 232 | U 233 | U 234 | U 235 | U 236 | U 237 | U 238 | U 239 | U 240 | U 241 | U 242 | U 243 | U 244 | U 245 | U 246 | U 247 | U 248 | U 249 | U 250

Faculté de chimie de l’université nationale autonome du Mexique

La mise en forme du texte ne suit pas les recommandations de Wikipédia : il faut le « wikifier ».

Les points d’amélioration suivants sont les cas les plus fréquents :

Pour une aide détaillée, merci de consulter Aide:Wikification.

Si vous pensez que ces points ont été résolus, vous pouvez retirer ce bandeau et améliorer la mise en forme d’un autre article.

La faculté de chimie de l’université nationale autonome du Mexique est une université de Tacuba au Mexique. Elle fait partie de l’université nationale autonome du Mexique.

La date clé est arrivée le 23 septembre 1916 lorsque, par décret présidentiel du président mexicain de l’époque, Venustiano Carranza, l’École nationale de chimie industrielle a été fondée dans la ville de Tacuba. En février de 1917 l’école a été incorporée à l’UNAM.

La Faculté de chimie est l’un des 27 établissements d’enseignement de l’Université nationale autonome du Mexique (UNAM). La Faculté mène des recherches en biochimie, chimie analytique, chimie organique, chimie physique, chimie alimentaire, la biotechnologie, la métallurgie, l’ingénierie chimie, chimie pharmaceutique, chimie inorganique, chimie nucléaire, chimie théorique et physique théorique. La faculté est organisée en 12 départements scientifiques et 4 unités. La Faculté de Chimie propose également 5 programmes d’études de 4,5 ans de durée pour l’obtention de baccalauréats  :

La plupart des bâtiments de la Faculté sont situés sur le campus principal de l’UNAM, Ciudad Universitaria, au sud de Mexico, tout a aussi deux campi étrangers, le Joint External Tacuba, Tacuba, la à l’ouest de Mexico, et à la station étrangère de Sisal, à Sisal, Yucatán. L’établissement offre également des programmes d’études de troisième cycle pour obtenir des diplômes de maîtrise et de doctorat dans plusieurs domaines

De plus, la Faculté offre plusieurs programmes de formation continue, ainsi qu’un large éventail de cours avancés et de diplômes.

NGC 4810

NGC 4810 is een onregelmatig sterrenstelsel in het sterrenbeeld Maagd. Het hemelobject werd op 18 april 1855 ontdekt door de Ierse astronoom William Parsons.

<<< · 4801 · 4802 · 4803 · 4804 · 4805 · 4806 · 4807 · 4807A · 4808 · 4809 · 4810 · 4811 · 4812 · 4813 · 4814 · 4815 · 4816 · 4817 · 4818 · 4819 · 4820 · 4821 · 4822 · 4823 · 4824 · 4825 · 4826 · 4827 · 4828 · 4829 · 4830 · 4831 · 4832 · 4833 · 4834 · 4835 · 4835A · 4836 · 4837-1 · 4837-2 · 4838 · 4839 · 4840 · 4841A · 4841B · 4842A · 4842B · 4843 · 4844 · 4845 · 4846 · 4847 · 4848 · 4849 · 4850 · 4851-1 · 4851-2 · 4852 · 4853 · 4854 · 4855 · 4856 · 4857 · 4858 · 4859 · 4860 · 4861 · 4862 · 4863 · 4864 · 4865 · 4866 · 4867 · 4868 · 4869 · 4870 · 4871 · 4872 · 4873 · 4874 · 4875 · 4876 · 4877 · 4878 · 4879 · 4880 · 4881 · 4882 · 4883 · 4884 · 4885 · 4886 · 4887 · 4888 · 4889 · 4890 · 4891 · 4892 · 4893 · 4894 · 4895 · 4895A · 4896 · 4897 · 4898-1 · 4898-2 · 4899 · 4900 · 4901 · 4902 · 4903 · 4904 · 4905 · 4906 · 4907 · 4908 · 4909 · 4910 · 4911 · 4911A · 4912 · 4913 · 4914 · 4915 · 4916 · 4917 · 4918 · 4919 · 4920 · 4921 · 4922-1 · 4922-2 · 4923 · 4924 · 4925 · 4926 · 4926A · 4926B · 4927 · 4928 · 4929 · 4930 · 4931 · 4932 · 4933 · 4933A · 4933B · 4933C · 4934 · 4935 · 4936 · 4937 · 4938 · 4939 · 4940 · 4941 · 4942 · 4943 · 4944 · 4945 · 4945A · 4946 · 4947 · 4947A · 4948 · 4948A · 4949 · 4950 · 4951 · 4952 · 4953-1 · 4953-2 · 4954 · 4955 · 4956 · 4957 · 4958 · 4959 · 4960 · 4961 · 4962 · 4963 · 4964 · 4965 · 4966 · 4967 · 4968 · 4969-1 · 4969-2 · 4970 · 4971 · 4972 · 4973 · 4974 · 4975 · 4976 · 4977 · 4978 · 4979 · 4980 · 4981 · 4982 · 4983 · 4984 · 4985 · 4986 · 4987 · 4988 · 4989 · 4990 · 4991 · 4992 · 4993 · 4994 · 4995 · 4996 · 4997 · 4998 · 4999 · 5000 · >>>

Armstrong Whitworth Sissit

The Armstrong Whitworth Sissit, also known as the Armstrong Whitworth F.K.1, was a prototype single-engined biplane fighter aircraft of the First World War. The first aircraft designed by Armstrong Whitworth, the Sissit was underpowered and only a single example was built.

In 1913, the British War Office asked the engineering company Sir W G Armstrong Whitworth & Co Ltd to manufacture aeroplanes and aircraft engines for the Army, and in response to that request, Armstrong Whitworth set up an aircraft department, hiring the Dutch designer Frederick Koolhoven, formerly chief engineer of British Deperdussin as chief designer.

Koolhoven’s first design for Armstrong Whitworth was a small, single-seat, aircraft intended as a scout aircraft. A single-bay tractor biplane, the Sissit, or F.K.1 was fitted with balanced elevators and no fixed tailplane.

Although designed for an 80 hp (60 kW) Gnôme rotary engine, only a 50 hp (37 kW) Gnôme could be obtained. Fitted with this engine, it was first flown by Koolhaven in September 1914. It proved to be underpowered, and was modified with a fixed tailplane and enlarged ailerons. As greatly superior single seat scout aircraft such as the Sopwith Tabloid and Bristol Scout were already available, no further development of the Sissit took place.

Data from British Aeroplanes 1914-18

General characteristics

Performance

Aircraft of comparable role, configuration and era

Øyefluer

Øyefluer er en familie av umiskjennelige fluer. Deres mest karakteristiske trekk er at fasettøynene er enormt store. Hos hannene dekker de hele det halvkuleformede hodet, hos hunnene er det en smal stripe mellom dem i pannen. Disse fluene er parasitter på sikader. Deres nærmeste slektningen er blomsterfluene. Øyefluene er vanlige, spesielt på gressmarker der sikadene de snylter på er tallrike, men blir lett oversett da de er ganske små og holder seg mest nede i vegetasjonen.

Øyefluene er lette å kjenne igjen hvis man en gang har sett en.

Hodet er meget stort, halvkuleformet til nesten helt kuleformet, og fasettøynene dekker nesten hele hodet. Hos hunnene er det en smal stripe i pannen mellom dem, men hos hannene møtes de i pannen. Bakerst i pannen sitter tre små punktøyne (ocelli). Antennene er små, tre-leddete, de to innerste leddene er små. En kraftig antennebørste (arista) sitter på oversiden av det tredje leddet, nær roten. Munndelene er små og knapt synlige fra siden.

Kroppen er påfallende kort, mye kortere enn vingene, vanligvis svart på farge men ofte med tett, grålig bestøvning. Brystet (thorax) har fin hårkledning men ingen kraftige børster.

Vingene er lange og smale. Hos de fleste gruppene går de to lengste årene (R4+5 og M1) mot hverandre ytterst i vingen slik at det dannes en linseformet celle.

Beina er temmelig korte, uten noen spesielle særtrekk.

Bakkroppen er sylindrisk, nokså kort. Hunnene har et spisst eggleggingsrør som de bruker til å bore eggene inn i vertsdyret.

Larvene er tykke, hvite med få tydelige ytre strukturer, et utseende som er typisk for larver som lever som parasitter inne i andre organismer.

Hele familien er parasitter på sikader (Auchenorrhyncha), og hunnene legger egg på nymfer eller voksne insekter. De legger bare ett egg på hvert vertsdyr. Larvene utvikler seg inne i verten, men tar ikke livet av den før de er ferdigutviklet. Til slutt har larven spist opp alle indre organer hos verten, de mest livsviktige til slutt. Den utvokste larven kryper ut av verten, som nå er redusert til et tomt skall, og forvandler seg til en puppe. En slik livssyklus, der larven spiser på en levende vert, men tar livet av den til slutt, kalles en parasitoid livssyklus. De voksne hunnene bruker sitt gode syn til å finne vertsdyr. Parringen skjer i luften. Øyefluene kan stå stille i luften liksom deres slektninger blomsterfluene, og hannene forfølger og griper hunner som passerer. Øyefluene er vanlige der sikadene de lever av er tallrike, særlig på blomsterenger eller lignende.

Mange av slektene er lite undersøkt i Norge, og det er sannsynlig at vi har en del flere arter enn de 40 som til nå er registrerte, da det finnes mange flere i våre naboland.