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Físicos de Princeton descubren estado cuántico exótico a temperatura ambiente

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Investigadores de Princeton han descubierto que un material conocido como aislante topológico, hecho de los elementos bismuto y bromo, exhibe comportamientos cuánticos especializados que normalmente solo se ven en condiciones experimentales extremas de altas presiones y temperaturas cercanas al cero absoluto. Crédito: Shafayat Hossain y el Sr. Zahid Hasan de la Universidad de Princeton

Por primera vez, los físicos han observado nuevos efectos cuánticos en un aislador topológico a temperatura ambiente.

Investigadores de[{» attribute=»»>Princeton University discovered that a material known as a topological insulator, made from the elements bismuth and bromine, exhibits specialized quantum behaviors normally seen only under extreme experimental conditions of high pressures and temperatures near absolute zero. The finding opens up a new range of possibilities for the development of efficient quantum technologies, such as spin-based, high-energy-efficiency electronics.

Physicists have observed novel quantum effects in a topological insulator at room temperature for the first time. This breakthrough came when scientists from Princeton University explored a topological material based on the element bismuth. The study was published as the cover article of the October issue of the journal Nature Materials.

While scientists have used topological insulators to demonstrate quantum effects for more than a decade, this experiment is the first time these effects have been observed at room temperature. Inducing and observing quantum states in topological insulators typically requires temperatures around absolute zero, which is equal to minus 459 degrees Fahrenheit (or -273 degrees Celsius).

This finding opens up a new range of possibilities for the development of efficient quantum technologies, such as spin-based electronics, which have the potential to replace many current electronic systems with substantially higher energy efficiency. 

In recent years, the study of topological states of matter has attracted considerable attention among physicists and engineers. In fact, it is presently the focus of much international interest and research. This area of study combines quantum physics with topology — a branch of theoretical mathematics that explores geometric properties that can be deformed but not intrinsically changed.

Zahid Hasan

M. Zahid Hasan. Credit: Princeton University

“The novel topological properties of matter have emerged as one of the most sought-after treasures in modern physics, both from a fundamental physics point of view and for finding potential applications in next-generation quantum engineering and nanotechnologies,” said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton University, who led the research. “This work was enabled by multiple innovative experimental advances in our lab at Princeton,” added Hasan.

A topological insulator is the main device component used to investigate the mysteries of quantum topology. This is a unique device that acts as an insulator in its interior, which means that the electrons inside are not free to move around and therefore do not conduct electricity. However, the electrons on the device’s edges are free to move around, meaning they are conductive. Moreover, because of the special properties of topology, the electrons flowing along the edges are not hampered by any defects or deformations. This device has the potential not only of improving technology but also of generating a greater understanding of matter itself by probing quantum electronic properties.

Until now, however, there has been a major stumbling block in the quest to use the materials and devices for applications in functional devices. “There is a lot of interest in topological materials and people often talk about their great potential for practical applications,” said Hasan, “but until some macroscopic quantum topological effect can be manifested at room temperature, these applications will likely remain unrealized.”

This is because ambient or high temperatures create what physicists call “thermal noise,” which is defined as a rise in temperature such that the atoms begin to vibrate violently. This action can disrupt delicate quantum systems, thereby collapsing the quantum state. In topological insulators, in particular, these higher temperatures create a situation in which the electrons on the surface of the insulator invade the interior, or “bulk,” of the insulator, and cause the electrons there to also begin conducting, which dilutes or breaks the special quantum effect.

The way around this is to subject such experiments to exceptionally cold temperatures, typically at or near absolute zero. At these incredibly low temperatures, atomic and subatomic particles cease vibrating and are consequently easier to manipulate. But creating and maintaining an ultra-cold environment is impractical for many applications; it is costly, bulky, and consumes a considerable amount of energy.

However, Hasan and his team have developed an innovative way to bypass this problem. Building on their experience with topological materials and working with many collaborators, they fabricated a new kind of topological insulator made from bismuth bromide (chemical formula α-Bi4Br4), which is an inorganic crystalline compound sometimes used for water treatment and chemical analyses.

“This is just terrific that we found them without giant pressure or an ultra-high magnetic field, thus making the materials more accessible for developing next-generation quantum technology,” said Nana Shumiya, who earned her Ph.D. at Princeton, is a postdoctoral research associate in electrical and computer engineering, and is one of the three co-first authors of the paper.

She added, “I believe our discovery will significantly advance the quantum frontier.”

The discovery’s roots lie in the workings of the quantum Hall effect — a form of topological effect that was the subject of the Nobel Prize in Physics in 1985. Since that time, topological phases have been intensely studied. Many new classes of quantum materials with topological electronic structures have been found, including topological insulators, topological superconductors, topological magnets, and Weyl semimetals.

While experimental discoveries were rapidly being made, theoretical discoveries were also progressing. Important theoretical concepts on two-dimensional (2D) topological insulators were put forward in 1988 by F. Duncan Haldane, the Sherman Fairchild University Professor of Physics at Princeton. He was awarded the Nobel Prize in Physics in 2016 for theoretical discoveries of topological phase transitions and a type of 2D topological insulators. Subsequent theoretical developments showed that topological insulators can take the form of two copies of Haldane’s model based on electron’s spin-orbit interaction.

Hasan and his team have been on a decade-long search for a topological quantum state that may also operate at room temperature, following their discovery of the first examples of three-dimensional topological insulators in 2007. Recently, they found a materials solution to Haldane’s conjecture in a kagome lattice magnet that is capable of operating at room temperature, which also exhibits the desired quantization.

“The kagome lattice topological insulators can be designed to possess relativistic band crossings and strong electron-electron interactions. Both are essential for novel magnetism,” said Hasan. “Therefore, we realized that kagome magnets are a promising system in which to search for topological magnet phases, as they are like the topological insulators that we discovered and studied more than ten years ago.”

“A suitable atomic chemistry and structure design coupled to first-principles theory is the crucial step to make topological insulator’s speculative prediction realistic in a high-temperature setting,” said Hasan. “There are hundreds of topological materials, and we need both intuition, experience, materials-specific calculations, and intense experimental efforts to eventually find the right material for in-depth exploration. And that took us on a decade-long journey of investigating many bismuth-based materials.

Insulators, like semiconductors, have what are called insulating, or band, gaps. These are in essence “barriers” between orbiting electrons, a sort of “no-man’s-land” where electrons cannot go. These band gaps are extremely important because, among other things, they provide the lynchpin in overcoming the limitation of achieving a quantum state imposed by thermal noise. They do this if the width of the band gap exceeds the width of the thermal noise. But too large a band gap can potentially disrupt the spin-orbit coupling of the electrons — this is the interaction between the electron’s spin and its orbital motion around the nucleus. When this disruption occurs, the topological quantum state collapses. Therefore, the trick in inducing and maintaining a quantum effect is to find a balance between a large band gap and the spin-orbit coupling effects.

Following a proposal by collaborators and co-authors Fan Zhang and Yugui Yao to explore a type of Weyl metals, Hasan and his team studied the bismuth bromide family of materials. But the researchers were not able to observe the Weyl phenomena in these materials. They instead discovered that the bismuth bromide insulator has properties that make it more ideal compared to a bismuth-antimony-based topological insulator (Bi-Sb alloys) that they had studied before. It has a large insulating gap of over 200 meV (“milli electron volts”). This is large enough to overcome thermal noise, but small enough so that it does not disrupt the spin-orbit coupling effect and band inversion topology.

“In this case, in our experiments, we found a balance between spin-orbit coupling effects and large band gap width,” said Hasan. “We found there is a ‘sweet spot’ where you can have relatively large spin-orbit coupling to create a topological twist as well as raise the band gap without destroying it. It’s kind of like a balance point for the bismuth-based materials that we have been studying for a long time.”

When the researchers viewed what was going on in the experiment through a sub-atomic resolution scanning tunneling microscope, they knew they had achieved their goal. This microscope is a unique device that uses a property known as “quantum tunneling,” where electrons are funneled between the sharp metallic, single-atom tip of the microscope and the sample. The microscope uses this tunneling current rather than light to view the world of electrons on the atomic scale. The team observed a clear quantum spin Hall edge state, which is one of the important properties that uniquely exist in topological systems. This required additional novel instrumentation to uniquely isolate the topological effect.

“For the first time, we demonstrated that there’s a class of bismuth-based topological materials that the topology survives up to room temperature,” said Hasan. “We are very confidant of our result.”

This finding is the culmination of many years of hard-won experimental work and required additional novel instrumentation ideas to be introduced in the experiments. Hasan has been a leading researcher in the field of experimental quantum topological materials with novel experimentation methodologies for over 15 years; and, indeed, was one of the field’s early pioneer researchers. Between 2005 and 2007, for example, he and his team of researchers discovered topological order in a three-dimensional bismuth-antimony bulk solid, a semiconducting alloy and related topological Dirac materials using novel experimental methods. This led to the discovery of topological magnetic materials. Between 2014 and 2015, they discovered a new class of topological materials called magnetic Weyl semimetals. The researchers believe this breakthrough will open the door to a whole host of future research possibilities and applications in quantum technologies.

 “We believe this finding may be the starting point of future development in nanotechnology,” said Shafayat Hossain, a postdoctoral research associate in Hasan’s lab and another co-first author of the study. “There have been so many proposed possibilities in topological technology that await, and finding appropriate materials coupled with novel instrumentation is one of the keys for this.”

One area of research where Hasan and his team believe this breakthrough will have particular impact is on next-generation quantum technologies. The researchers believe this new breakthrough will hasten the development of more efficient, and “greener” quantum materials.

Currently, the theoretical and experimental focus of the group is concentrated in two directions, said Hasan. First, the researchers want to determine what other topological materials might operate at room temperature, and, importantly, provide other scientists the tools and novel instrumentation methods to identify materials that will operate at room and high temperatures. Second, the researchers want to continue to probe deeper into the quantum world now that this finding has made it possible to conduct experiments at higher temperatures.

These studies will require the development of another set of new instrumentations and techniques to fully harness the enormous potential of these materials. “I see a tremendous opportunity for further in-depth exploration of exotic and complex quantum phenomena with our new instrumentation, tracking more finer details in macroscopic quantum states,” Hasan said. “Who knows what we will discover?”

“Our research is a real step forward in demonstrating the potential of topological materials for energy-saving applications,” added Hasan. “What we’ve done here with this experiment is plant a seed to encourage other scientists and engineers to dream big.”

Reference: “Evidence of a room-temperature quantum spin Hall edge state in a higher-order topological insulator” by Nana Shumiya, Md Shafayat Hossain, Jia-Xin Yin, Zhiwei Wang, Maksim Litskevich, Chiho Yoon, Yongkai Li, Ying Yang, Yu-Xiao Jiang, Guangming Cheng, Yen-Chuan Lin, Qi Zhang, Zi-Jia Cheng, Tyler A. Cochran, Daniel Multer, Xian P. Yang, Brian Casas, Tay-Rong Chang, Titus Neupert, Zhujun Yuan, Shuang Jia, Hsin Lin, Nan Yao, Luis Balicas, Fan Zhang, Yugui Yao and M. Zahid Hasan, 14 July 2022, Nature Materials.
DOI: 10.1038/s41563-022-01304-3

The team included numerous researchers from Princeton’s Department of Physics, including present and past graduate students Nana Shumiya, Maksim Litskevich, Yu-Xiao Jiang, Zi-Jia Cheng, Tyler Cochran and Daniel Multer, and present and past postdoctoral research associates, Shafayat Hossain, Jia-Xin Yin and Qi Zhang. Other co-authors were Zhiwei Wang, Chiho Yoon, Yongkai Li, Ying Yang, Guangming Cheng , Yen-Chuan Lin, Brian Casas, Tay-Rong Chang, Titus Neupert , Zhujun Yuan, Shuang Jia , Hsin Lin  and Nan Yao .

The work at Princeton was supported by the U.S. Department of Energy’s Basic Energy Sciences Division (and the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative.

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La Vía Láctea es demasiado grande para su «muro cosmológico»

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Una galaxia análoga solitaria de la Vía Láctea, demasiado masiva para su pared. La imagen de fondo muestra la distribución de materia oscura (verde y azul) y galaxias (aquí vistas como pequeños puntos amarillos) en una fina porción del volumen cúbico en el que esperamos encontrar una de estas raras galaxias masivas. Crédito: Imágenes: Miguel A. Aragon-Calvo, Datos de simulación: Proyecto Illustris TNG (CC BY 4.0)

La Vía Láctea resulta ser más única de lo que pensábamos

Es el[{» attribute=»»>Milky Way special, or, at least, is it in a special place in the Universe? An international team of astronomers has found that the answer to that question is yes, in a way not previously appreciated. A new study shows that the Milky Way is too big for its “cosmological wall,” something yet to be seen in other galaxies. The new research is published in Monthly Notices of the Royal Astronomical Society.

A cosmological wall is a flattened arrangement of galaxies found surrounding other galaxies, characterized by particularly empty regions called ‘voids’ on either side of it. These voids seem to squash the galaxies together into a pancake-like shape to make the flattened arrangement. This wall environment, in this case, called the Local Sheet, influences how The Milky Way and nearby galaxies rotate around their axes, in a more organized way than if we were in a random place in the Universe, without a wall.

Typically, galaxies tend to be significantly smaller than this so-called wall. The Milky Way is found to be surprisingly massive in comparison to its cosmological wall, a rare cosmic occurrence.

Milky Way Analog Wall of Galaxies

A Milky Way Analogue sitting at the center of a flat wall of smaller galaxies (grey spheres). The blue circles indicate distance from the Milky Way Analogue in 1 Mpc intervals. The background image shows the distribution of dark matter (green and blue) and galaxies (here seen as tiny yellow dots) in a thin slice of the cubic volume in which we expect to find one of such rare massive galaxies. Credit: Images: Miguel A. Aragon-Calvo, Simulation Data: Illustris TNG project (CC BY 4.0)

The new findings are based on a state-of-the-art computer simulation, part of the IllustrisTNG project. The team simulated a volume of the Universe nearly a billion light-years across that contains millions of galaxies. Only a handful – about a millionth of all the galaxies in the simulation – were as “special” as the Milky Way, i.e. both embedded in a cosmological wall like the Local Sheet, and as massive as our home galaxy.

According to the team, it may be necessary to take into account the special environment around the Milky Way when running simulations, to avoid a so-called “Copernican bias” in making scientific inference from the galaxies around us. This bias, describing the successive removal of our special status in the nearly 500 years since Copernicus demoted the Earth from being at the center of the cosmos, would come from assuming that we reside in a completely average place in the Universe. To simulate observations, astronomers sometimes assume that any point in a simulation such as IllustrisTNG is as good as any, but the team’s findings indicate that it may be important to use precise locations to make such measurements.

Local Sheet Surrounding Milky Way

The Local Sheet, a flat wall of galaxies surrounding the Milky Way (indicated by a spiral pattern). The blue circles indicate distance from the Milky Way in 1 Mpc intervals. Credit: Images: Miguel A. Aragon-Calvo, Simulation Data: Illustris TNG project

“So, the Milky Way is, in a way, special,” said research lead Miguel Aragón. “The Earth is very obviously special, the only home of life that we know. But it’s not the center of the Universe, or even the Solar System. And the Sun is just an ordinary star among billions in the Milky Way. Even our galaxy seemed to be just another spiral galaxy among billions of others in the observable Universe.”

“The Milky Way doesn’t have a particularly special mass, or type. There are lots of spiral galaxies that look roughly like it,” Joe Silk, another of the researchers, said. “But it is rare if you take into account its surroundings. If you could see the nearest dozen or so large galaxies easily in the sky, you would see that they all nearly lie on a ring, embedded in the Local Sheet. That’s a little bit special in itself. What we newly found is that other walls of galaxies in the Universe like the Local Sheet very seldom seem to have a galaxy inside them that’s as massive as the Milky Way.”

Local Sheet Milky Way Analogs

A Local Sheet Analogue in the Illustris TNG300 simulation, a flat wall of galaxies surrounding a Milky Way Analogue galaxy (large sphere at the center). The blue circles indicate distance from the central galaxy in 1 Mpc intervals. Credit: Images: Miguel A. Aragon-Calvo, Simulation Data: Illustris TNG project

“You might have to travel a half a billion light years from the Milky Way, past many, many galaxies, to find another cosmological wall with a galaxy like ours,” Aragón said. He adds, “That’s a couple of hundred times farther away than the nearest large galaxy around us, Andromeda.”

“You do have to be careful, though, choosing properties that qualify as ‘special,’” Dr. Mark Neyrinck, another member of the team, said. “If we added a ridiculously restrictive condition on a galaxy, such as that it must contain the paper we wrote about this, we would certainly be the only galaxy in the observable Universe like that. But we think this ‘too big for its wall’ property is physically meaningful and observationally relevant enough to call out as really being special.”

Reference: “The unusual Milky Way-local sheet system: implications for spin strength and alignment” by M A Aragon-Calvo, Joseph Silk and Mark Neyrinck, 23 December 2022, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnrasl/slac161

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Hay una ‘ciudad perdida’ en el fondo del océano, y no se parece a nada que hayamos visto: ScienceAlert

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Cerca de la cima de una montaña submarina al oeste de la Cordillera del Atlántico Medio, un paisaje irregular de torres se eleva desde la oscuridad.

Sus paredes y columnas de carbonato cremoso parecen de un azul fantasmal a la luz de un vehículo a control remoto enviado a explorar.

Varían en altura de pequeñas pilas del tamaño de hongos venenosos forman un gran monolito de 60 metros (casi 200 pies) de altura. Es la ciudad perdida.

Un vehículo a control remoto ilumina las agujas de la ciudad perdida. (D. Kelley/UW/URI-IAO/NOAA).

Descubierto por científicos en 2000, más de 700 metros (2,300 pies) debajo de la superficie, El campo hidrotermal de Ciudad Perdida es el entorno de ventilación más longevo que se conoce en el océano. Nunca se ha encontrado nada igual.

Durante al menos 120.000 años y posiblemente más, el manto ascendente en esta parte del mundo ha reaccionado con el agua de mar para empujar hidrógeno, metano y otros gases disueltos al océano.

En las grietas y hendiduras de los respiraderos del campo, los hidrocarburos alimentan nuevas comunidades microbianas incluso sin la presencia de oxígeno.

Bacterias en columna de calcita.
Hebras de bacterias que viven en un respiradero de calcita en la Ciudad Perdida. (Universidad de Washington/CC POR 3.0).

Chimeneas que escupen gases hasta 40°C (104°F) son el hogar de una gran cantidad de caracoles y mariscos. Los animales más grandes, como cangrejos, camarones, erizos de mar y anguilas, son raros, pero aún están presentes.

A pesar de la naturaleza extrema del medio ambiente, parece estar lleno de vida, y los investigadores creen que merece nuestra atención y protección.

Si bien es probable que existan otros respiraderos hidrotermales como este en otros lugares de los océanos del mundo, es el único que los vehículos operados a distancia han podido encontrar hasta ahora.

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Los hidrocarburos producidos por los respiraderos de Ciudad Perdida no se formaron a partir del dióxido de carbono atmosférico o la luz solar, sino a través de reacciones químicas en el lecho marino profundo.

Debido a que los hidrocarburos son los componentes básicos de la vida, deja abierta la posibilidad de que la vida se haya originado en un hábitat como este. Y no solo en nuestro propio planeta.

«Es un ejemplo de un tipo de ecosistema que podría estar activo en Encelado o Europa en este momento», dijo el microbiólogo William Brazelton. Relata el smithsonian en 2018, refiriéndose a las lunas de Saturno y Júpiter.

«Y tal vez marzo en el pasado.»

A diferencia de los respiraderos volcánicos submarinos llamados fumadores negrosque también fueron designados como el primer hábitat posible, el ecosistema de la Ciudad Perdida no depende del calor del magma.

Los negros humeantes producen principalmente minerales ricos en hierro y azufre, mientras que las chimeneas de la ciudad perdida producen hasta 100 veces más hidrógeno y metano.

Los respiraderos de calcita de Lost City también son mucho, mucho más grandes que los humos negros, lo que sugiere que han estado activos por más tiempo.

Gran Ventilación de la Ciudad Perdida
Chimenea de nueve metros de altura en la Ciudad Perdida. (Universidad de Washington/Instituto de Oceanografía Woods Hole).

El más alto de los monolitos se llama Poseidón, en honor al dios griego del mar, y mide más de 60 metros de altura.

Justo al noreste de la torre, mientras tanto, hay un acantilado con breves estallidos de actividad. Investigadores de la Universidad de Washington describir los respiraderos aquí como ‘llorar’ con fluido para producir ‘racimos de crecimientos de carbonato delicados y de múltiples puntas que se extienden hacia afuera como los dedos de las manos hacia arriba’.

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Desafortunadamente, los científicos no son los únicos atraídos por este terreno inusual.

En 2018 se anunció que Polonia había ganó los derechos para explotar las profundidades del mar alrededor de La Ciudad Perdida. Si bien no hay recursos valiosos para extraer del propio campo de calor, la destrucción de los alrededores de la ciudad podría tener consecuencias no deseadas.

Cualquier columna o liberación, provocada por la minería, podría extenderse fácilmente sobre este notable hábitat, advierten los científicos.

Por lo tanto, algunos expertos son llamando por la Ciudad Perdida en la Lista del Patrimonio Mundial, para proteger la maravilla natural antes de que sea demasiado tarde.

Durante decenas de miles de años, la ciudad perdida se ha mantenido como testimonio de la fuerza perdurable de la vida.

Sería como si lo estropeáramos.

Una versión anterior de este artículo se publicó en agosto de 2022.

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AAC Clyde Space formará parte del primer satélite GEO Space Situational Awareness (SSA) de Europa – SatNews

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Un consorcio que incluye AAC Espacio de Clydeafiliado, AAC Hiperiónfue seleccionado por Fondo Europeo de Defensa desarrollar un satélite <100 kg para ser colocado en GEO para conciencia situacional espacial (CULO).

El satélite, llamado náucratesno debe ser rastreable desde un radar terrestre, telescopio óptico o radiotelescopio y se espera que sea el primer satélite GEO europeo para SSA en GEO.

Con su experiencia en determinación de actitud y sistemas de control, AAC Hyperion suministrará los componentes del prototipo. Como socio del consorcio, AAC Hyperion también participará en el diseño del bus satelital, su prototipo, así como en la integración y las pruebas. Este proyecto se beneficia de una financiación del Fondo Europeo de Defensa (EDF) de 0,7 millones de euros acuerdo de subvención 101102517 – NAUCRATES – EDF-2021-OPEN-D. Se espera que el satélite se entregue en 2026.

Europa, con su flota de satélites GEO militares y comerciales, necesita cada vez más capacidades independientes de control y vigilancia del espacio. El satélite Naucrates desempeñará un papel clave en la capacidad de Europa para realizar SSA.

El satélite se posicionará en una órbita estable fuera del cinturón GEO para no perturbar a otros satélites o transmisiones, con la capacidad de acercarse a otros objetos GEO para tomar imágenes con resolución centimétrica. Contará con un telescopio óptico que utiliza infrarrojos especiales para la transmisión de imágenes a fin de minimizar la posibilidad de espionaje.

Los satélites en GEO permanecen exactamente sobre el ecuador a aprox. 36.000 kilómetros, sin cambiar su posición relativa a una ubicación en la Tierra. El satélite Naucrates será lanzado directamente a GEO por un Ariadna 6 y podría permanecer en órbita de 3 a 5 años.

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«Estamos orgullosos de ser parte de este proyecto de vanguardia, que impulsará aún más las capacidades de los satélites pequeños y contribuirá a un entorno orbital más seguro.«, dijo el director ejecutivo de AAC, Clyde Space, luis gomes.

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