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Articoli del 15/03/2012

The technique (developed by an international team of scientists in the United States and the United Kingdom), which is the first of its kind to use high-pressure chemistry for making well-developed films and wires of this particular kind of silicon semiconductor, will help scientists to make more-efficient and more-flexible optical fibers. The findings, by an international team led by John Badding, a professor of chemistry at Penn State University, will be published in a future print edition of the Journal of the American Chemical Society.

Badding explained that hydrogenated amorphous silicon -- a noncrystalline form of silicon -- is ideal for applications such as solar cells. Hydrogenated amorphous silicon also would be useful for the light-guiding cores of optical fibers; however, depositing the silicon compound into an optical fiber -- which is thinner than the width of a human hair -- presents a challenge. "Traditionally, hydrogenated amorphous silicon is created using an expensive laboratory device known as a plasma reactor," Badding explained. "Such a reactor begins with a precursor called silane -- a silicon-hydrogen compound. Our goal was not only to find a simpler way to create hydrogenated amorphous silicon using silane, but also to use it in the development of an optical fiber."

A bed of amorphous hydrogenated silicon wires that were prepared in the pores of optical fibers. The wires have been chemically etched out of the optical fiber to reveal them. Scale bar is 100 um. Inset: An array of amorphous hydrogenated silicon tubes deposited in an optical fiber. The optical fiber has been cleaved in half to reveal the array of tubes. The very thin glass walls of the fiber surrounding each tube are largely obscured. Scale bar is 5um. Credit: John Badding lab, Penn State University.

Because traditional, low-pressure chemistry techniques cannot be used for depositing hydrogenated amorphous silicon into a fiber, the team had to find another approach. "While the low-pressure plasma reactor technique works well enough for depositing hydrogenated amorphous silicon onto a surface to make solar cells, it does not allow the silane precursor molecules to be pushed into the long, thin holes in an optical fiber," said Pier J. A. Sazio of the University of Southampton in the United Kingdom and one of the team's leaders. "The trick was to develop a high-pressure technique that could force the molecules of silane all the way down into the fiber and then also convert them to amorphous hydrogenated silicon. The high-pressure chemistry technique is unique in allowing the silane to decompose into the useful hydrogenated form of amorphous silicon, rather than the much less-useful non-hydrogenated form that otherwise would form without a plasma reactor. Using pressure in this way is very practical because the optical fibers are so small."

Optical fibers with a non-crystalline form of silicon have many applications. For example, such fibers could be used in telecommunications devices, or even to change laser light into different infrared wavelengths. Infrared light could be used to improve surgical techniques, military countermeasure devices, or chemical-sensing tools, such as those that detect pollutants or environmental toxins. The team members also hope that their research will be used to improve existing solar-cell technology. "What's most exciting about our research is that, for the first time, optical fibers with hydrogenated amorphous silicon are possible; however, our technique also reduces certain production costs, so there's no reason it could not help in the manufacture of less-expensive solar cells, as well," Badding said.

Source: Pennsylvania State University via


Camminando per lo spazio espositivo di Peep-Hole vedrete molte luci accendersi. Non si tratta, però, di una mostra di design o di lampade d'autore. Gli interruttori sono a Rio de Janeiro, nella casa di Renata Lucas, artista brasiliana che espone a Milano l' impianto elettrico della sua abitazione in Brasile nell'installazione Third Time.

Le lampade - tutte al neon, per accentuarne la presenza negli spazi - sono nell'esatta posizione originale dall'altra parte del mondo e si accendono quando la Lucas, banalmente, le accende a casa sua. L'installazione utilizzza un impianto di domotica che consente il coordinamento dei due impianti elettrici che fanno dell'artista il collante tra la sua abitazione e la galleria milanese, giocando con la sua assenza/presenza. E annullando i 9mila chilometri di distanza.

L'ispirazione per l'opera nasce da un fatto curioso: nel 1931 l'illuminazione della Statua del Cristo Redentore a Rio, nel giorno della sua inaugurazione, venne attivata via radio proprio dall'Italia pare - anche se non vi è la certezza - da Guglielmo Marconi. Third Time è visitabile fino al 4 di febbraio, presso Peep-Hole.



În unele tari sunt realizate operatii de schimbare a culorii ochilor cu ajutorul unor mici discuri din silicon, dar multi medicii oftalmologi afirma ca aceste proceduri, departe de a fi inofensive, pot duce la probleme oculare grave, mergând pâna la pierderea vederii.

Medicii avertizează: implanturile care schimbă culoarea ochilor pot duce la pierderea vederii

În urma cu trei ani, Beatriz Murillo, care este pictorita si locuieste în Canada, a platit 8.000 dolari pentru o operatie de schimbare a culorii ochilor (din caprui în verzi), calatorind în acest scop în Panama, la o clinica specializata, deoarece aceasta operatie nu este permisa în Canada.

De atunci, ea a fost nevoita sa suporte doua interventii chirugicale pentru glaucom (o boala care se manifesta prin cresterea presiunii intraoculare si poate duce la orbire) si o alta pentru un transplant de cornee, care, însa, nu a reusit. Astazi, desi implanturile au fost îndepartate, pictorita în vârsta de 36 de ani este aproape oarba, putând vedea doar niste vagi umbre colorate.

Dr. Ike Ahmed, chirurg oftalmolog la Credit Valley Hospital din Mississauga, Canada, care a tratat câteva cazuri similare, avertizeaza asupra faptului ca aceste implanturi irita ochii, producând inflamatii, hemoragii oculare si aparitia glaucomului.

La ora actuala, afirma el, nu exista o metoda chirugicala sigura de a schimba culoarea ochilor unei persoane. Pentru cei care tin cu tot dinadinsul sa îsi modifice culoarea cu care i-a înzestrat natura, e mai sigura solutia simpla, temporara, a lentilelor de contact colorate.

Sursa: cbc - via


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