El CNA pone en marcha un servicio de diagnóstico por imagen mediante un dispositivo PET-CT
El Centro Nacional de Aceleradores (CNA), centro de investigación formado por la Universidad de Sevilla, la Junta de Andalucía y el Consejo Superior de Investigaciones Científicas (CSIC), oferta por primera vez a la comunidad médica investigadora nacional e internacional su equipo PET/CT para la realización de investigación y ensayos clínicos con pacientes.
El equipamiento que el Centro de Diagnóstico por Imagen del CNA, CDI-CNA, pone a disposición de la comunidad investigadora para este tipo de estudios es un equipo híbrido PET/CT de última generación que permite obtener información tanto funcional como anatómica del paciente. Se trata de un escáner PET/CT fabricado por Siemens, modelo Molecular CT (mCT-64).
Read more »» El CNA pone en marcha un servicio de diagnóstico por imagen mediante un dispositivo PET-CT
Wednesday, May 16th, 2012,
by Manuel,
Filed under: Acelerador de particulas,Ciencia,CNA,CPAN,CSIC,Cuántica,España,Fisica,Fisica de alta energia,Fisica de particulas,Fisica Nuclear,Science,Technology,Tecnologia |
| Ciencia, CNA, cpan, CSIC, España, Fisica de particulas, Fisica Nuclear, Investigacion, PET, Science, Tecnologia, Tomografía por Emisión de Positrones|
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LHCb discovers two excited states for the Λb beauty particle
The new excited states show clear signals at masses of 5912 MeV/c2 and 5920 MeV/c2 (Image: LHCb collaboration)
The Large Hadron Collider beauty (LHCb) experiment at CERN today announced that it has observed two new excited states of the Λb beauty baryon. Though the Standard Model of particle physics predicts the existence of these new states, this is the first time they have been confirmed in an experiment.
Baryons are subatomic particles whose mass is equal to or greater than that of a proton. Like protons and neutrons, the Λb beauty baryon is composed of three quarks. In Λb these are up, down and beauty quarks.
LHCb physicists found the signals for the ?b particlesin a sample of about 60 trillion proton—proton collisions which were delivered by the LHC operating at a centre-of-mass energy of 7 TeV in 2011. They measured the masses of the new excited states as 5912 MeV/c2 and 5920 MeV/c2 respectively – over five times greater than the mass of a proton or neutron.
The result adds to a growing list of discoveries at CERN in recent months. Last month the Compact Muon Solenoid (CMS) experiment observed a new excited state for the ?b beauty baryon, and back in December 2011 ATLAS detected a new “quarkonium state” containing a beauty quark bound with its antiquark.
http://public.web.cern.ch/public/
Find out more:
LHCb result
16 May 2012: First observation of two excited states of Λb.
The quark model, independently proposed by physicists Murray Gell-Mann and George Zweig in 1964 to classify the strongly interacting particles called hadrons, is very successful. In this model baryons are composed of three quarks and mesons are composed of quark-antiquark pairs. The simplest baryon, the proton, which is the nucleus of the hydrogen atom, is composed of three light quarks uud while its neutral partner the neutron is composes of udd quarks. By replacing one of the d quarks by a heavier strange quark s we obtain a Λ particle composed of uds quarks. Furthermore by replacing in the Λ the s quark by a charm quark c or a beauty quark b we obtain a Λc or a Λb particle.
The three quarks forming the Λ, Λc and ?b are in their lowest quantum mechanical state. Like electrons in atoms quarks can form excited states with different values of angular momentum and quark spin orientation. These excited states were previously observed for the Λ and Λc particles. They were, however, never observed for the <Λsub>b particle.
The LHCb collaboration has made first observations of two excited states of Λb.
click the image for higher resolution
The Λb excited states have been reconstructed in three steps. In the first step the Λc+ particles were reconstructed through their decay into a proton p, a negative K- meson and a positive Λ+ meson. In the second step the Λc particles were combined with negative Λ- mesons in order to form the Λb particles. The Λb signal is clearly seen as the enhancement in the left image above showing the Λc+Λ- invariant mass spectrum. Finally the Λb particles have been combined with a pair of opposite sign pions Λ+Λ-. In the right image above two enhancements are clearly seen corresponding to the two Λb excited states with masses of 5912 and 5920 MeV, about 6 times the proton mass.
LHCb physicists have observed about 16 Λb(5912)ΛbΛ+?- decays (4.9 Λsignificance) and about 50 Λb(5920)Λ?bΛ+Λ- decays (10.1?) among about 60 million million (6*1013) pp collisions seen by the LHCb detector at LHC during the 2011 data taking period.
http://lhcb-public.web.cern.ch/lhcb-public/
Read more in CERN Bulletin article and LHCb publication.
Wednesday, May 16th, 2012,
by Manuel,
Filed under: Acelerador de particulas,CERN,Ciencia,Cosmologia,Cuántica,Fisica,Fisica de alta energia,Fisica de particulas,Fisica Nuclear,Fisica Teorica,LHCB experiment,Matematicas,Materia,Mecanica cuantica,Science |
| Astrofisica, CERN, Ciencia, Cosmologia, Fisica, Fisica de particulas, Fisica Teorica, LHC, LHCB, Matematicas, Science|
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Two beautiful new particles
In beautiful agreement with the Standard Model, two new excited states (see below) of the Λb beauty particle have just been observed by the LHCb Collaboration. Similarly to protons and neutrons, Λb is composed of three quarks. In the Λb’s case, these are up, down and… beauty.
Although discovering new particles is increasingly looking like a routine exercise for the LHC experiments (see previous features), it is far from being an obvious performance, particularly when the mass of the particles is high. Created in the high-energy proton-proton collisions produced by the LHC, these new excited states of the Λb particle have been found to have a mass of, respectively, 5912 MeV/c2 and 5920 MeV/c2. In other words, they are over five times heavier than the proton or the neutron.
Physicists only declare a discovery when data significantly show the relevant signal. In order to do that, they often have to analyse large samples of data. To obtain its beautiful result, the LHCb Collaboration has analysed the information coming from about 60 million million (6x1013) proton-proton collisions collected during the 2011 data-taking period. In particular, since the excited states only survive for a very short time before decaying, physicists carefully studied the decay products and tracked the whole process back to the decay vertex. The analysis took scientists several months to complete but today they are able to present the discovery with very high statistical significance, namely 4.9 σ for the first excited state and 10.1 for the second one.
Although never observed before, the excited states of the Λb particle were expected to exist according to the Standard Model, the theory that tells us how quarks combine to build particles and matter. The LHCb result is therefore a new confirmation of the success of the theory itself.
EXCITED STATES OF MATTER
Matter can be formed in different energy states. The most stable one – that is, the one that survives the longest before decaying – is the so-called “ground state”, in which particles have the lowest possible energy. States with higher energy are called “excited states”. They are still allowed by Nature but they are unstable. The higher the formation energy (i.e. the mass) the more unstable they are.
Read more about this result on the LHCb Public Webpage.
Wednesday, May 16th, 2012,
by CERN,
Filed under: CERN,Ciencia,Cosmologia,Fisica,Fisica de alta energia,Fisica de Materiales,Fisica de particulas,LHC,Matematicas,Materia,Mecanica cuantica,Science,Sincrotrón |
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Los agujeros negros ‘apagan’ la formación estelar en las galaxias del universo lejano
El estudio, que publica Nature y en el que han participado investigadores del IAC, indica que los agujeros negros controlan, mediante los rayos X que se emiten a su alrededor, el número de estrellas que se forman en una galaxia
Este trabajo ayudaría a resolver uno de los enigmas de la década: por qué las masas de los agujeros negros supermasivos están relacionadas con las masas de los grupos centrales de estrellas en la galaxia
Estos resultados han sido posibles gracias a las observaciones obtenidas con la cámara SPIRE del Observatorio Espacial Herschel de la ESA, en el marco del proyecto HerMES
Un equipo internacional de astrofísicos agrupados en el proyecto HerMES, en el que participa el Instituto de Astrofísica de Canarias (IAC), ha descubierto que el número de estrellas que se forman durante la vida temprana de las galaxias puede ser controlado por los agujeros negros masivos de sus núcleos. El hallazgo, que publica hoy la revista Nature, ayudará a contestar la pregunta de por qué la masa de los bulbos galácticos, las concentraciones centrales de estrellas en las galaxias, parece estar relacionada con la masa de sus agujeros negros.
Uno de los hallazgos de los últimos años ha sido que las galaxias con agujeros negros masivos presentan ritmos altos de formación estelar, con casos en los que se forman estrellas a un ritmo incluso mil veces mayor al de la Vía Láctea en la actualidad.
Read more »» Los agujeros negros ‘apagan’ la formación estelar en las galaxias del universo lejano
Monday, May 14th, 2012,
by Manuel,
Filed under: Agujeros Negros,Astrofisica,Astronomia,Ciencia,Cuántica,Fisica,Galaxias,Gravedad,IAC,Nasa,Relatividad,Science,Universo |
| Agujeros negros, Astrofisica, Astronomia, Ciencia, Cosmologia, Fisica, IAC, Science|
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CHARM of Hawaii
I’m blogging from the site of CHARM-2012 conference, which has just started in Honolulu, Hawaii. This is a fantastic conference at a fantastic place! The conference will have four full-packed days filled with many aspects of physics related to charmed quark. As I reported earlier, many exciting recent results are associated with charm quark.
Why is the conference taking part in Hawaii? Besides being a nice place in general, it is almost exactly half way between Japan and the US. This meeting alternates between Asian, US and European locations, and last meeting, in 2009, was in Beijing — so it is US’ turn. There will be many talks from KEK‘s Belle collaboration (which University of Hawaii is a member of), LHC experiments, as well as from Tevatron experiments. Besides, world’s only operating charm experiment (BES 3) is located in Beijing, China. Indeed, there would be many theory talks as well. It shapes to be a very nice conference — and I’ll be reporting about exciting results to be discussed here.
Monday, May 14th, 2012,
by CERN,
Filed under: CERN,Ciencia,Cosmologia,Fisica,Fisica de alta energia,Fisica de Materiales,Fisica de particulas,LHC,Matematicas,Materia,Mecanica cuantica,Science,Sincrotrón |
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Sale a la luz el calendario maya más antiguo
El estudio se publica en el último número de ‘Science’
Por este motivo en este sitio que solo tratamos de ciencia queremos enfocar este tema como arqueologico.
Somos conscientes que puede provocar malentendidos, sobretodo por las magufadas del año 2012.
Esperamos que lo veais como simple Astronomia , Arqueolgia e Historia.
Hasta ahora se conocían las tablas astronómicas del último periodo maya, como los códices de Dresde o Madrid escritos en corteza de árbol sobre el siglo XIV, pero ahora investigadores de la Universidad de Boston (EEUU) las han descubierto pintadas en la pared de una vivienda del periodo clásico, cinco siglos antes. El taller de un astrónomo en la megaciudad maya de Xultún, en Guatemala, guardaba el secreto.
Bajo un montículo cubierto de vegetación en la selva del Petén, en Guatemala, investigadores de EEUU han descubierto una sala pintada con pictogramas numéricos que se corresponden con los ciclos lunares y, posiblemente, con los de algunos planetas. El estudio, que publica esta semana la revista Science, ha contado con el apoyo de National Geographic.
Read more »» Sale a la luz el calendario maya más antiguo
Sunday, May 13th, 2012,
by Manuel,
Filed under: Arqueologia,Astronomia,Centroamerica,Ciencia,Cultura,Documentales,Historia,Science |
| Arqueologia, Astronomia, Ciencia, Gutemala, Historia, Mayas, Science|
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Happy birthday, Richard Feynman!
Richard Feynman was one of the most influential physicists of the twentieth century. Not only did he revolutionize quantum theory with his development of quantum electrodynamics, but he also revolutionized the way we think about physics and physicists. He spoke to people from all kinds of backgrounds about physics, from lecturing students destined to change the field themselves, to appearing on television to discuss physics and the philosophy of science, to meeting with the greatest minds of the time.
Feynman in the middle of a lecture. (www.richard-feynman.net)
For me, Feyman’s great contribution was the way he thought about physics. His Lectures on Physics are world famous, and rightly so. (In fact, one of the first things I did after landing in San Francisco to work at SLAC was to buy a copy of his lectures from the Stanford bookstore. Shortly afterwards by bank froze my card, suspecting fraud. It was worth the inconvenience!)
As a jaded undergraduate they were a source of inspiration to me. A faint glimmer of hope turned into a roaring inferno after reading his lectures on electromagnetism, and I’ve never looked back since. Finally, here was someone who wanted to discuss the beauty of the subject, as well as the truth. He had no time for obscuring the underlying symmetry of a concept, nor for lying to students in order to make things easier. Inevitably having to unlearn and relearn ideas leaves people confused, disillusioned and unable to trust their tutors. In that spirit, this is how he started his course on electromagnetism:
“We begin now our detailed study of the theory of electromagnetism. All of electromagnetism is contained in the Maxwell equations.
Maxwell’s equations:
\[
\nabla \cdot \vec{E} = \frac{\rho}{\varepsilon_0}
\]
\[
\nabla \times \vec{E} = - \frac{\partial \vec{B}}{\partial t}
\]
\[
c^2\nabla \times \vec{B} = \frac{\partial \vec{E}}{\partial t} + \frac{\vec{j}}{\varepsilon_0}
\]
\[
\nabla \cdot \vec{B} = 0
\]
Don’t worry about trying to understand these equations. The important thing here is that Feynman has given the students the complete truth about electromagnetism. With these four equations he can solve any problem about the shape and nature of electromagnetic fields for any configuration of charges and currents. The equations he provides are not some approximation of the theory, or some equations that only work some of the time, these are the equations that all physicists and engineers use and they are, as far as we know, complete and state of the art. Feynman has shown a level of honesty and respect for his students/readers that was not present when I sat through lectures. My lecturers taught me backwards, Feynman taught me forwards.
(Experts might notice that the Lorentz force law is missing here, but Feynman already mentioned it a few pages before Maxwell’s equations. With the Lorentz force law physicists can relate the electromagnetic fields to the forces on charged particles.)
Feynman continues:
The situations that are described by these equations can be very complicated. We will consider first relatively simple situations, and learn how to handle them before we take up more complicated. The easiest circumstance to treat is one in which nothing depends on time- called the static case. All charges are permanently fixed in space, or if they do move, they move as a steady flow in a circuit (so \(\rho\) and \(\vec{j}\) are constant in time). In these circumstances, all of the terms in the Maxwell equations which are time derivatives of the field are zero. In this case Maxwell’s equations become:
Electrostatics:
\[
\nabla \cdot \vec{E} = \frac{\rho}{\varepsilon_0}
\]
\[
\nabla \times \vec{E} = \vec{0}
\]magnetostatics:
\[
c^2\nabla \times \vec{B} = \frac{\vec{j}}{\varepsilon_0}
\]
\[
\nabla \cdot \vec{B} = 0
\]You will notice an interesting thing about this set of four equations. It can be separated into two pairs. The electric field \(\vec{E}\) appears only in the first two, and the magnetic field \(\vec{B}\) appears only in the second two. The two fields are not interconnected. This means that electricity and magnetism are distinct phenomena so long as charges and currents are static.
And he goes on. Immediately at the start of the course he’s pointed out one of the most important and beautiful symmetries in electromagnetism. He also lets us know how the course is going to proceed, with static cases first and the full treatment later. This leaves the student with a wonderful surprise later in the course, when the two fields finally get united again. When this happens Feynman goes on to show us how electromagnetism comes about as a result of special relativity, and if done properly that is one of the most breathtaking moments in physics! This is the way physics should be taught, and I wish I could have been in that lecture hall to see it happen!
The rest of the lectures are a fascinating journey, full of neat little asides, teasers, paradoxes, and it’s all handled with refreshing clarity. He even pokes fun at physics itself from time to time, showing how our mathematical notation is just a trick to make complicated things look simple and how different problems appear to have similar solutions only because we choose to use the same kinds of methods to solve them. Towards the end of his electromagnetism course he even goes out of his way to show how electromagnetism fails in an epic way. The problem of the infinite energy of the field, and the intractable problem of the mass of the electron are two major failings of the classical theory, and he dedicates a lecture to showing us just many questions were left unanswered by the subject.
Feynman with bongos, because some physicists are cool (www.richard-feynman.net)
Feynman gave us a lot to digest, from Nobel prize worthy discoveries, to a view of scientists that was anything but a crusty old professor, and for me what I value most is the lectures he gave, packed with inspiration and clarity. If you have a chance, go read some of the lectures and find out what made this man get out of bed in the morning. You won’t be disappointed. His other books are also excellent (Six Easy Pieces, Six Not So Easy Pieces, QED and Surely You’re Joking, Mr Feynman!) and well worth a read. Put them on your Christmas wish list!
Feynman’s birthday should be a national day of celebration, not just for physics, but for getting people hooked on physics! (I’m just sorry I’m a bit late to the party here, have a great weekend.)
If you want to find out a bit more about Richard Feynman check out this lecture about Feynman from Lawrence Krauss, one of today’s most eloquent speakers and best advocates for physics.
(Quotes taken from “The Feyman Lectures on Physics, The Definitive Edition Volume II”, Feynman Leighton and Sands, ISBN 0-8053-9047-2)
Friday, May 11th, 2012,
by CERN,
Filed under: CERN,Ciencia,Cosmologia,Fisica,Fisica de alta energia,Fisica de Materiales,Fisica de particulas,LHC,Matematicas,Materia,Mecanica cuantica,Science,Sincrotrón |
| Physics|
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Science and Engineering: vive la Différence
This essay was motivated by a question from an engineering colleague. It would be presumptuous to say “friend,” as scientist and engineers are in a state of “friendly” rivalry, however, not to the extent as with arts. I once saw a sign in an engineering department hallway that read: Friends do not let friends study arts. Be that as it may, my colleague’s question was why scientists do not show the same order in all their work as they show in writing papers. That question I will attempt to answer in this essay.
Engineering is far older than science, being perhaps the second oldest profession, dating back at least to the building of the pyramids (Imhotep from the 27th century BCE is the oldest named engineer) and Stonehenge and probably back to when the first club was engineered. Stonehenge is amazing as it was probably built without the documentation that is the hallmark of modern engineering practice. Unfortunately, that means we do not know what the initial requirements[1] were and this has led to much futile speculation as to its purpose.
Science and engineering are sibling disciplines, frequently mentioned together and have much in common. The main similarity is that they both deal with the observable universe and are judged by their ability to make correct predictions regarding its behaviour. For example, that the Higgs boson will be found at the Large Hadron Collider (LHC) or that the building will not collapse in an earthquake. Secondarily they use similar techniques, placing high importance on analytic reasoning, to the extent that Asperger’s syndrome is sometimes called the engineer’s disease. The relation between Asperger’s syndrome and engineers or scientists may be an urban myth but it does indicate the relation of extreme analytic thought to both science and engineering. The solution to problems in both relies on the same problem solving skills, analytic thinking and mathematics. Do not let anyone tell you that either does not require a high degree of intellectual activity.
Science and engineering rely on each other. Behind every engineering project is a great deal of science, from the basic understanding of Newtonian mechanics in the building of a bridge to the advanced materials science in the construction of a cell phone. Actually, the cell phone is a good example of all the science needed: it depends on Newtonian mechanics (the construction of the cell phone towers), quantum mechanics (the operation of the transistors), classical electromagnetism i.e. Maxwell’s equations (the propagation of the signal from the tower to the cell phone), materials science (almost all the cell phone itself), and general and special relativity (the GPS timing that is necessary in some cell phone technologies).
Equally, science is beholden to engineering. From simple things like the buildings that house scientific equipment to complicated things like the ATLAS detector at the Large Hadron Collider (LHC). Making a building may seem simple but, as I see with the new ARIEL building at TRIUMF, nothing is simple and even something as basic as a laboratory building relies on engineering expertise. The ATLAS detector is another story. Its size and complexity are a marvel of engineering virtuosity. Back to TRIUMF, the IEEE has recognized the TRIUMF cyclotron, commissioned in 1974 and the main driver for much of TRIUMF’s science program, as an Engineering Milestone. Even the slide rule I used back in ancient history as an undergraduate[2] was an engineering achievement.
Despite the close relationship between science and engineering the two are different. The difference can be summarized in this statement: “In engineering you do not start a project unless you know the answer while in science you do not start a project if you know the answer.” Engineering is based on everything being predictable; you do not start building a bridge unless you know you can complete it. In science, the purpose of a project is to answer a question to which the answer is currently unknown. For example, if the properties of the Higgs boson were known, it would not have been necessary to build the LHC. Good engineering practice is based on order but at the center of science is chaos. We are exploring the unknown; great discoveries can come from serendipity. In science, something not working as expected can lead to the next big breakthrough. In engineering, something not working as expected can lead to the bridge collapsing. Advances in science are frequently due to creativity, not following rules.
This difference in perspective leads to very different cultures in the two disciplines. The engineer is much more concerned with process and following procedure. The scientist with following up his most recent hunch—after all, it could lead to a Nobel Prize. Engineering versus science: order versus creative chaos. This is clearly an oversimplification as there is no clean separation between engineering and science, but it is a good indication of the divergence between the two mindsets. Thus, although engineering and science are closely related and indeed intertwined, the two, in their heart of hearts, are very different; engineering uses science in order to build and science uses engineering in order to explore.
Additional posts in this series will appear most Friday afternoons at 3:30 pm Vancouver time. To receive a reminder follow me on Twitter: @musquod.
[1] Project management jargon alert: requirements used in technical project management sense.
[2] HP produced the first pocket calculator when I was an undergraduate student.
Friday, May 11th, 2012,
by CERN,
Filed under: CERN,Ciencia,Cosmologia,Fisica,Fisica de alta energia,Fisica de Materiales,Fisica de particulas,LHC,Matematicas,Materia,Mecanica cuantica,Science,Sincrotrón |
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Universo con un principio
Recientes estudios apuntan a que el Universo tuvo que tener un principio, incluso cuando se considera la inflación eterna, el universo cíclico o la singularidad desnuda eterna.
Read more »» Universo con un principio
Friday, May 11th, 2012,
by Manuel,
Filed under: Antimateria,Antimatter,Astrofisica,Big Bang,Ciencia,Cosmologia,Cuántica,Dark energy,Dark matter,Fisica,Fisica de alta energia,Fisica de particulas,Fisica Nuclear,Fisica Teorica,Gravedad,Matematicas,Materia,Mecanica cuantica,Relatividad,Science,String Theory,Supersimetria,SUSY,Universo |
| Astrofisica, Ciencia, Cosmologia, Fisica, Fisica de particulas, Fisica Nuclear, Fisica Teorica, Matematicas, Materia Oscura, Mecanica cuantica, Science, Universo|
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No hay uno sino varios universos
Si había algún tema en el que existía un consenso amplio, incluso entre científicos y religiosos, ese era el origen del Universo. Paul Steinhardt, físico y cosmólogo de la Universidad de Princeton y autor del libro Endless Universe, ha concebido un modelo teórico que desconcierta a los religiosos y sorprende a los académicos. Según el modelo cíclico de Steinhardt, el cosmos no tiene principio ni fin.
El Universo ha comenzado hace 13.700 millones de años tras el Big Bang. La materia que hoy conforma miles de millones de galaxias y billones de estrellas estuvo comprimida en un punto más pequeño que una cabeza de alfiler, momento en que comenzó a existir el tiempo y el espacio. ¿Cómo sucedió la creación del universo a partir de la nada? Para los científicos, la respuesta es un misterio pero, para muchos religiosos, un escenario muy cómodo en el que situar a Dios como el origen de todas las cosas.
Read more »» No hay uno sino varios universos
Friday, May 11th, 2012,
by Manuel,
Filed under: Science |
| Astrofisica, CERN, Ciencia, Cosmologia, Fisica, Fisica de particulas, Fisica Nuclear, LHC, Matematicas, Mecanica cuantica, Science, Universo|
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Particle Physics Foundations of Dark Matter-Dark Energy-and Inflatio Resubida
 |
Particle Physics Foundations of Dark Matter, Dark Energy, and Inflation (1/3) © CERN Kolb, Edward (Rocky) (speaker) (University of Chicago) CERN. Geneva Academic Training Lecture Regular Programme Ninety-five percent of the present mass-energy density of the Universe is dark. Twenty-five percent is in the form of dark matter holding together galaxies and other large scale structures, and 70% is in the form of dark energy driving an accelerated expansion of the universe. Dark matter and dark energy cannot be explained within the standard model of particle physics. In the first lecture I will review the evidence for dark matter and the observations that point to an explanation in the form of cold dark matter. I will then describe the expected properties of a hypothetical Weakly-Interacting Massive Particle, or WIMP, and review experimental and observational approaches to test the hypothesis. Finally, I will discuss how the LHC might shed light on the problem. In the second lecture I will review the theoretical foundations and observational evidence that the dominant component of the present mass density of the Universe has a negative pressure, which leads to an accelerated expansion of the Universe. I will then describe various approaches to understand the phenomenon. Finally, I will describe an observational program to understand the nature of dark energy. The third lecture will describe the issues and models associated with primordial inflation, the purported rapid <b>...</b> |
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Thursday, May 10th, 2012,
by admin,
Filed under: CERN,Ciencia,Cosmologia,Fisica,Fisica de alta energia,Fisica de Materiales,Fisica de particulas,LHC,Matematicas,Materia,Mecanica cuantica,Science,Sincrotrón |
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La mecánica cuántica logra explicar propiedades de las nanoantenas ópticas
Una investigación del Consejo Superior de Investigaciones Científicas (CSIC) ha desarrollado un marco teórico que describe las propiedades subnanométricas de las nanoantenas ópticas. El nuevo modelo resuelve las características de este régimen especial de distancias gracias a la mecánica cuántica, que completa las explicaciones basadas en ecuaciones de física clásica. El trabajo ha sido publicado hoy en la revista Nature Communitacions.
Las nanopartículas metálicas actúan como antenas ópticas, ya que aumentan la recepción, el control y la emisión de radiación óptica. Este efecto se consigue a través de la excitación colectiva de los electrones del metal y, hasta ahora, sólo había sido descrito por las ecuaciones establecidas por James Clerck Maxwell (ecuaciones de Maxwell) hace más de un siglo.
El avance de la tecnología ha ido reduciendo los tamaños y las distancias de separación entre las nanoantenas metálicas. Este proceso ha dado lugar a nuevas propiedades que la física clásica es incapaz de describir, tales como el transporte de electrones por efecto túnel, basado en la probabilidad de dichos electrones de desaparecer de un electrodo y reaparecer en el otro.
El investigador del Centro de Física de Materiales del CSIC Javier Aizpurua, que ha dirigido el trabajo, cuenta que “hasta ahora estas propiedades sólo podían describirse de forma aproximada cuando las distancias de interacción alcanzan valores por debajo del nanómetro”. El modelo propuesto por el equipo de Aizpurua permite abordar de forma compacta la “enorme cantidad de electrones involucrada en la respuesta óptica de una nanoestructura y los efectos cuánticos que aparecen a distancias subnanométricas”, añade.
Según el investigador del CSIC, “el hallazgo abre un nuevo camino para calcular y diseñar los efectos cuánticos en antenas ópticas clásicas y en dispositivos optoelectrónicos”. De la misma forma, todos estos efectos cuánticos tienen “una gran importancia en diversas disciplinas como la bioquímica, la electrónica molecular y las comunicaciones ópticas”, concluye Aizpurua.
El trabajo ha contado con la colaboración de investigadores del Instituto de Colisiones Atómicas y Moleculares de Orsay (Francia) y del Laboratorio de Nanofotónica de Houston (EEUU).
Rubén Esteban, Andrei G. Borison, Peter Nordlander y Javier Aizpurua. Bridging quantum and classical plasmonics with quantum-corrected model. Nature Communications. DOI: 10.1038/ncomms1806
Thursday, May 10th, 2012,
by Manuel,
Filed under: Ciencia,CSIC,Cuántica,Fisica,Mecanica cuantica,Science |
| Ciencia, CSIC, Cuántica, Fisica, Mecanica cuantica, Optica, Science|
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