WorldWideScience

Sample records for vantaggi che si

  1. Emanuele Liaci, Il gatto che si mordeva la coda

    OpenAIRE

    Lucia Pascale

    2012-01-01

    Il gatto che si mordeva la coda (Le Chat qui se mordait la queue) est le premier livre du poloniste et professeur Emanuele Liaci (1976). Sur un arrière-fond autobiographique, ce roman à la première personne fait interagir Ferdy Durke, Gingio pour les intimes, une figure inspirée du roman de Witold Gombrowicz, avec Mattia Pascal, un célèbre personnage de la littérature italienne né sous la plume de Luigi Pirandello. L’histoire commence à Rome, le héros-narrateur doit entamer son premier jour d...

  2. Emanuele Liaci, Il gatto che si mordeva la coda

    Directory of Open Access Journals (Sweden)

    Lucia Pascale

    2012-07-01

    Full Text Available Il gatto che si mordeva la coda (Le Chat qui se mordait la queue est le premier livre du poloniste et professeur Emanuele Liaci (1976. Sur un arrière-fond autobiographique, ce roman à la première personne fait interagir Ferdy Durke, Gingio pour les intimes, une figure inspirée du roman de Witold Gombrowicz, avec Mattia Pascal, un célèbre personnage de la littérature italienne né sous la plume de Luigi Pirandello. L’histoire commence à Rome, le héros-narrateur doit entamer son premier jour d...

  3. La chiesa che si fa presepe: visita al Presepe della Chiesa del Rosario di Mottola

    Directory of Open Access Journals (Sweden)

    Susy Bigontina

    2012-01-01

    Full Text Available Abstract – IT In occasione del Natale, la vie della città di Mottola (Ta, Italia fioriscono di presepi, che i visitatori possono liberamente ammirare. Quella del presepe è una tradizione molto sentita dagli abitanti della cittadina pugliese, nella quale viene allestito un grande presepe che occupa e cela l’intera navata della Chiesa del Ss. Sacramento e Rosario. Gli allestitori, appartenenti ad una storica Confraternita locale dedicano settimane a costruire un presepe plastico della Betlemme nella notte di Natale, che mescola icone della tradizione italiana della Natività – alcuni pezzi, ad esempio, sono preziosi manufatti di scuola napoletana – ed elementi naturali tipici della terra delle gravine. Il presepe del Rosario, inoltre, mostra un’interessante ricerca dell’effetto prospettico e forse un ancor più interessante cornice di ciclicità, ottenuta tramite l’alternanza del giorno e della notte, musica ed effetti sonori, che proietta la scena verso un orizzonte atemporale. Questo articolo nasce dalla visita degli autori a Mottola, in occasione della presentazione del libro La Settimana Santa a Mottola, di cui essi sono stati co-autori, e quindi rappresenta il frutto di un nuovo capitolo di lavoro con la viva comunità mottolese ed i suoi riti. Abstract – FR Pour l'occasion de Noël, les rues de la villes de Mottola (Ta, Italie sont embellies de crèches que les visiteurs peuvent admirer en toute liberté. La tradition de la crèche est une tradition très ressentie par les habitants de la petite ville pugliaise, dans laquelle on prépare une grande crèche qui occupe et cache tout le nef de l'église du très Ss. Sacramento e Rosario. Les préparateurs qui appartiennent à une Confrérie historique locale dédient plusieurs semaines pour la construction d'une crèche comme celle de Betleemme de la nuit de Noël - certaines pièces, par exemple, sont de précieux produits manufacturés provenant de l'école napolitaine - et

  4. Che cos’è la filosofia

    Directory of Open Access Journals (Sweden)

    Maria Chiara Pievatolo

    2011-09-01

    Full Text Available Ecco una risposta che arriva dagli antipodi, tramite il blog di John Wilkins: filosofia è quello che si fa quando i fatti non assicurano una soluzione. Wilkins usa tutta la ricchezza di riferimenti che ci può aspettare da una disciplina con una bibliografia millenaria. Ma la finezza della definizione sta nel suo carattere elementare: se [...

  5. Sostenere le produzioni cinematografiche: vantaggi fiscali e di immagine per gli investitori / Sustaining cinematographic productions: fiscal and image opportunities for investors

    Directory of Open Access Journals (Sweden)

    Katia Giusepponi

    2016-05-01

    Full Text Available Questo contributo è focalizzato su organizzazioni non appartenenti al settore cinematografico, osservate nel loro ruolo di investitori esterni. L’importanza del valore collettivo di sostenere le produzioni cineaudiovisive è alla base del presente lavoro. Tuttavia la nostra attenzione è qui rivolta, da un lato, a studiare i vantaggi dell’investimento per l’azienda esterna, dall’altro, ad analizzarne i rischi nella prospettiva di una sempre più chiara consapevolezza di scelta. Dall’analisi di strumenti, dinamiche e dati emergono opportunità rilevanti per l’azienda, insieme a condizioni importanti per utilizzarle con successo. È essenziale che l’organizzazione proceda senza improvvisare, curando, da un lato, un approccio alla pianificazione e alla dettagliata valutazione del progetto, dall’altro, flessibilità e apertura nelle interazioni con gli altri interlocutori, interazioni che devono essere orientate al raggiungimento dell’equilibrio migliore a livello collettivo e individuale. Soprattutto, è necessario che l’azienda proceda nel contesto di un percorso strategico solido e coerente, perché un progetto di film può valorizzare l’identità aziendale ma non risolvere incertezze a questo riguardo.   This contribution focuses on organisations that are not in the cinema industry, studied in their role as external investors. The importance of the collective value of sustaining cine audio visual productions is at the basis of this work. Nonetheless, our attention is oriented, on one hand, to study the investment advantages for the external organization, on the other, to analyse the risks of this investment in the perspective of an increasingly clear choice. From the analysis of tools, dynamics and data, relevant opportunities for the organisation emerge, together with important conditions for their successful implementation. It is essential that the organization proceed without improvising, following, on one side, an

  6. El humanismo del Che Che's Humanism

    Directory of Open Access Journals (Sweden)

    Avelino Fernández Espert

    2004-08-01

    Full Text Available Los autores, estudiosos de la raigal influencia del pensamiento y la obra del Comandante Dr. Ernesto Guevara de la Serna (Che en Cuba y América, proyectan la estampa humanista de este revolucionario médico, con el empleo de las más trascendentes pinceladas históricas de un amplia hoja de vida en distintas latitudes del mundo. El Che, joven estudiante, médico graduado con prometedoras dotes que sabe ubicar al ser humano y sus valores por encima de un promisorio futuro como científico y profesional de la medicina. El artículo dedica atención especial a sus conceptos sobre el hombre, su vida e historia y a su proverbial apego a una ética revolucionaria de elevado calibre. El artículo contribuye al enriquecimiento de los conocimientos sobre el desarrollo histórico del humanismo médico cubano, al proyectarlo en la figura de uno de sus más míticos modelosThe authors, studious of the extraordinary influence of Commandant and Dr. Ernesto Guevara de la Serna 's thought in Cuba and America, unveil the humanist perspective of this revolutionary doctor, through the most transcendental historical events in this man's life in different latitudes of the world. Che, young student, medicine doctor with promising gifts that knew how to place the human being and his values above his promissory future as scientific and medicine professional. The article dedicates special attention to his concepts about men, as well as his life and history and to his proverbial attachment to valuable revolutionary ethics. The article contributes to the enrichment of knowledge on the historical development of Cuban medical humanism, by reflecting this in the figure of one of its most mythical models

  7. Il piu grande centro europeo di ricerca oggi festeggia l'anniversario del Nobel di Rubbia e Van der Meer. Cern, vent'anni guardando al futuro Ora la sfida si gioca sull'acceleratore di particelle pronto per il 2007, che provera a svelare i segreti della materia

    CERN Document Server

    Durante, E

    2003-01-01

    "CERN, vent'anni guardando al futuro Ora la sfida si gioca sull'acceleratore di particelle pronto per il 2007, che provera a svelare i segreti della materia" [CERN, twenty years of looking towards the future. The present challenge is the particle accelerator that will be ready in 2007, which will try to reveal the secrets of matter] (2 pages)

  8. Che cos’è l’antiziganismo?

    Directory of Open Access Journals (Sweden)

    Leonardo Piasere

    2012-01-01

    Full Text Available Abstract – IT Chi è zingaro? Colui che chiamo zingaro, che assegno a questa identità e che costituisco come "altro" dal resto della società. In questo senso, la storia degli zingari si confonde con quella dell'"antiziganismo", un neologismo che denota una pratica antica. Ma si può dire che la comparsa della nuova parola è legata agliodierni intrecci tra politiche multiculturali da un lato e politiche neoliberiste dall’altro?Abstract – FRQui est Tsigane? Celui que je nomme Tsigane, que j'assigne à cette identité et que je constitue en "autre" du reste de la société. Dans ce sens, l'histoire des Tsiganes se confond avec celle de l'"antitsiganisme", un néologisme qui recouvre une pratique ancienne. Mais peut-on dire que l'apparition de ce nouveau mot estliée aux croisements actuels entre les politiques multiculturelles d'une part, et les politiques néolibéralesde l'autre? Abstract – EN Who is Gypsy? The person I call Gypsy, to whom I assign this identity, is that I establish as "other" than the rest of society. In this sense, the history of Gypsies merges with that of "antigypsism", a neologism that denotes an ancient practice. But can it be said that the appearance ofthis new word is linked to the current entanglement between multi-cultural politics on one side and neo-liberalist politics on the other?

  9. Perché io credo in colui che ha fatto il mondo

    CERN Document Server

    Zichichi, Antonino

    1999-01-01

    Fin troppo spesso si sente dire che il mondo della scienza e quello della religione sono in completa opposizione e che non condividono alcuna esperienza o caratteristica in comune. Nulla potrebbe essere più falso di queste affermazioni secondo Antonino Zichichi, che in quest'opera afferma come la ricerca scientifica e l'esperienza religiosa abbiano in comune molto più di quanto si possa pensare.

  10. Altruisti, cooperativi e morali: Perché è più facile esserlo domani che oggi

    NARCIS (Netherlands)

    Giacomantonio, M.; de Dreu, C.K.W.

    2013-01-01

    Un portafogli smarrito e ritrovato. Una donazione ad un ente che si occupa di ricerca sulle malattie degenerative. Una tangente non accettata. Un divorzio che si conclude senza il ricorso al tribunale. Alla base di tutti questi eventi vi è la tendenza umana a cooperare, ad essere altruisti e ad

  11. Capitolo III. Che cos’è una società?

    OpenAIRE

    Tarde, Gabriel

    2016-01-01

    Il nostro concetto di società risulta molto chiaramente da quanto precede, ma è importante precisare ulteriormente questa nozione fondamentale. I Che cos’è una società? Si è risposto generalmente: un gruppo di individui diversi che si aiutano a vicenda. Da questa definizione, tanto falsa quanto chiara, sono sorte tutte le confusioni stabilitesi molto frequentemente tra le cosiddette società animali, o la maggior parte di esse, e le sole vere società, tra le quali ve ne sono, da un certo punto...

  12. Il diabete che migra

    Directory of Open Access Journals (Sweden)

    Angela Infante

    2009-04-01

    Full Text Available Nel gennaio 2007 ha avuto inizio il “Corso di Counseling e Terapie Interculturali”; nello stesso gennaio il Servizio di Diabetologia Pediatrica dell’Azienda Universitaria Ospedaliera Policlinico Tor Vergata di Roma ha richiesto la mia collaborazione per un progetto relativo all’alleanza e all’aderenza terapeutica del minore straniero affetto da diabete mellito. Ho avuto l’opportunità di partecipare a questo progetto, poiché avevo avuto precedenti esperienze nel Servizio di Medicina Solidale e delle Migrazioni, progetto del medesimo Policlinico. Questo progetto riguarda tutti i minori autoctoni e migranti affetti dalla suddetta patologia, in cura presso l’Unità Operativa di Diabetologia Pediatrica. Il mio ruolo principale all’interno del progetto è quello di apportare un doppio ascolto medico-counselor durante le visite di controllo, che possono variare a seconda dell’andamento della patologia, da una cadenza mensile ad una quindicinale. Durante questi colloqui il mio primo intento è quello di approcciarmi alla famiglia in un’ottica sistemica, in seguito di affrontare una ricostruzione autobiografica della storia familiare e del processo migratorio.

  13. Che-1 gene silencing induces osteosarcoma cell apoptosis by inhibiting mutant p53 expression

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ming; Wang, Dan, E-mail: danwangwdd@163.com; Li, Ning

    2016-04-22

    The transcriptional cofactor Che-1 is an RNA polymerase II (Pol II) which is involved in tumorigenesis, such as breast cancer and multiple myeloma. Che-1 can also regulate mutant p53 expression, which plays roles in many types of cancer. In this study, we aimed to investigate the effects and specific mechanism of Che-1 in the regulation of osteosarcoma (OS) cell growth. We found that Che-1 is highly expressed in several kinds of OS cells compared with osteoblast hFOB1.19 cells. MTT and flow cytometry assays showed that Che-1 depletion by siRNA markedly suppressed MG-63 and U2OS cell proliferation and promoted apoptosis. The chromatin immunoprecipitation (ChIP) assay verified the presence of Che-1 on the p53 promoter in MG-63 and U2OS cells carrying mutant p53. Further studies showed that Che-1 depletion inhibited mutant p53 expression. Notably, our study showed that the loss of Che-1 inhibits proliferation and promotes apoptosis in MG-63 cells by decreasing the level of mutant p53. Therefore, these findings open the possibility that silencing of Che-1 will have therapeutic benefit in OS. - Highlights: • Che-1 is highly expressed in several kinds of OS cells. • Che-1 depletion suppressed MG-63 and U2OS cell growth. • Che-1 is existed in the p53 promoter in MG-63 and U2OS cells. • Che-1 depletion inhibited mutant p53 expression. • Che-1 depletion inhibits cell growth by decreasing the level of mutant p53.

  14. Le portrait de Che Guevara

    OpenAIRE

    Maguet, Frédéric

    2013-01-01

    Frédéric Maguet, Le portrait de Che Guevara. Comment la parole vient à l’icône – Depuis plus de quarante ans, le portrait de Che Guevara au béret étoilé a été une image très largement reproduite dans les contextes les plus divers, du militantisme politique à l’industrie du design. La perspective retenue ici est celle de sa réception en France et en Europe. Dès la mort du Che en 1967, ce portrait est massivement diffusé dans l’espace public et devint un symbole de la rébellion en général, disp...

  15. Che: His Own Worst Enemy

    Science.gov (United States)

    2015-04-01

    failure to capitalize may be attributed to another tactical mistake. 18 Not long after the guerrilla band had been exposed, after several bouts with...Michael. The Marxism of Che Guevara: Philosophy, economics, and revolutionary warfare. New York: Monthly Review Press, 1973. LW-518. Leaders in Irregular

  16. Introduzione. Donne che portano la parrucca

    Directory of Open Access Journals (Sweden)

    Claudia Mattalucci-Yılmaz

    2013-07-01

    Full Text Available Peruk takan kadınlar è l’opera che nel 1999 l’artista e cineasta turco Kutlug Ataman ha presentato alla Biennale di Venezia curata da Harald Szeemann. Quattro schermi giustapposti proiettano le testimonianze di donne che, per un periodo della loro vita, hanno portato una parrucca: un’attivista politica di sinistra che nel 1971, dopo il colpo di stato militare, utilizzava un nome in codice, una divisa delle Turkish Airlines e una parrucca per sfuggire al controllo della polizia; una giornalista, colpita da un tumore al seno, che ha portato una parrucca per mascherare gli effetti della chemioterapia; una studentessa musulmana che indossa una parrucca per frequentare l’università, in un contesto – quello turco – che in nome della laicità dello Stato, interdice l’uso nel foulard nelle scuole, nelle università e nella pubblica amministrazione; e infine un transessuale.

  17. I sei numeri dell'universo le forze profonde che spiegano il cosmo

    CERN Document Server

    Rees, Martin

    2002-01-01

    È possibile che sei semplici numeri, sei costanti universali, diano conto dell'infinita varietà e della stupefacente complessità del cosmo? L'astrofisico Martin Rees ci mostra che non soltano ciò è possibile, ma in quei sei numeri sono scritti la storia, la struttura e il futuro dell'universo, e che perfino la comparsa della vita sulla terra, e dunque la nostra stessa esistenza, non sarebbe concepibile se uno solo di quei valori numerici, definiti nell'istante che segnò la nascita del mondo, fosse differente. I sei numeri dell'universo ci introducono così ad alcune delle questioni più profonde su cui si interroga oggi la scienza.

  18. Che cos’è il collettivo?

    OpenAIRE

    Nancy, Jean-Luc

    2016-01-01

    1. Che cos’è un “collettivo”, una collettività o una comunità? In cosa consiste l’essere insieme? Non consiste solamente nel trovarsi gli uni accanto agli altri. Bisogna che l’essere “accanto” sia esso stesso compreso come altra cosa rispetto alla pura e semplice simultaneità contingente in un medesimo spazio. Non è una questione di spazio-tempo e neppure di “uno” e “parecchi” secondo una qualche aritmetica. Vorrei mostrare che il collettivo comincia con e nel singolare, lo fonda nel momento ...

  19. Il marchio che gode di rinomanza

    OpenAIRE

    Caselli, Sara

    2014-01-01

    I marchi famosi sono quei marchi che, essendo riusciti ad affermarsi sul mercato, esprimono più di tutti i segni distintivi il significato attribuito al marchio inteso come strumento di comunicazione. Da ciò deriva la necessità di riconoscere loro una tutela adeguata contro usi che possano pregiudicare il loro selling power. La tutela dei marchi che godono di rinomanza ha conosciuto, dalla sua introduzione avvenuta nel '92 con l'attuazione della Direttiva 104/89/CEE ad oggi, per effetto sopra...

  20. Il fantasma dell'universo che cos'è il neutrino

    CERN Document Server

    Votano, Lucia

    2015-01-01

    Ben prima della luce, a un decimillesimo di secondo dal Big Bang, i neutrini sono apparsi nell'universo. Dopo un secondo il brodo primordiale si era raffreddato abbastanza da consentire loro di muoversi liberi e ancora oggi, dopo quasi quattordici miliardi di anni, sono numerosissimi. Ma che cosa sono i neutrini? Elusivi come fantasmi, camaleontici, viaggiano indenni attraverso la materia arrivando dritti sino a noi dagli angoli più remoti e nascosti dell'universo. Per saperne di più seguiremo i fisici che li studiano in laboratori sotterranei o in luoghi estremi come i ghiacciai polari o le profondità marine.

  1. Crèche and School

    CERN Multimedia

    EVE et École

    2018-01-01

    IMPORTANT DATES Enrolments 2018-2019 Enrolments to the Crèche and School for the school year 2018-2019 will take place on 5, 6 and 7 March 2018 from 10 am to 1 pm at the Crèche and School of the CERN Staff Association. Registration forms will be available from Thursday 1st March 2018. For more information, please visit the website: http://nurseryschool.web.cern.ch/. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Saturday 3 March 2018 Open Day at Crèche and School of the CERN Staff Association Are you considering enrolling your child to the Crèche and School of the CERN Staff Association? If you work at CERN, then this event is for you: come visit the school and meet the Management on Saturday 3 March 2018 from 10 to 12 am It will be our pleasure to present to you our structure, its projects and premises, and answer any questions you may have. Please sign up for one of the two sessions via Doodle before Wednesd...

  2. Che legend elab ka 40 aastat hiljem / Evelyn Kaldoja

    Index Scriptorium Estoniae

    Kaldoja, Evelyn, 1980-

    2007-01-01

    Ilmunud ka: Postimees : na russkom jazõke 9. okt. lk. 10. Argentinas sündinud ja 1967. aastal hukatud revolutsionääri Ernesto Che Guevara poliitikukarjäärist, tema panusest Kuuba revolutsiooni ja poliitikasse. Ernesto Che Guevara mälestamisest Ladina-Ameeerika riikides. Lisa: Kuuba revolutsioon; Che Guevara elu

  3. La macchina che cerca Dio. Nasce LHC forse scoprira' Higgs elusiva particella della creazione

    CERN Multimedia

    Bianucci, P

    2003-01-01

    "LEON Lederman, premio Nobel per la fisica, l'ha misticamente definita la particella di Dio perche' sarebbe il pilastro sul quale si appoggia tutta la materia dell'universo che conosciamo. Piu' tecnicamente, e' la "particella di Higgs", un bosone previsto dal Modello Standard del microcosmo la cui esistenza sarebbe necessaria per giustificare, anche quantitativamente, la massa di tutte le particelle" (1/2 page).

  4. «Oh che armonico fracasso»: un percorso didattico sul "Maestro di cappella" di Domenico Cimarosa

    Directory of Open Access Journals (Sweden)

    Nicola Badolato

    2011-04-01

    Full Text Available Si presume che Domenico Cimarosa (1749-1801 abbia composto Il maestro di cappella tra il 1786 e il 1791 a Pietroburgo, dov’era stato invitato dalla zarina Caterina II. Non si conosce un autografo della musica, né un libretto. Un’unica fonte tramanda il brano, uno spartito per canto e piano edito a Lipsia da Hofmeister intorno al 1813, che lo definisce "ein burleskes Intermezzo" (intermezzo burlesco.Il percorso didattico qui proposto si indirizza alle classi dell’ultimo biennio della Scuola primaria; si lascia eventualmente estendere al prim’anno della Secondaria di primo grado.

  5. La nascita imperfetta delle cose la grande corsa alla particella di Dio e la nuova fisica che cambierà il mondo

    CERN Document Server

    AUTHOR|(CDS)2068901

    2016-01-01

    In quel preciso momento, un centesimo di miliardesimo di secondo dopo il Big Bang, si è deciso il nostro destino. In un universo in cui materia e antimateria si equivalevano, e che quindi avrebbe potuto, in ogni istante, tornare a essere pura energia, può essere bastata una leggerissima preferenza del bosone di Higgs per la materia anziché per l'antimateria ed ecco che si è prodotto il mondo che abbiamo sotto gli occhi. "Ecco qua il minuscolo difetto, la sottile imperfezione da cui è nato tutto. Un'anomalia che dà origine a un universo che può evolvere per miliardi di anni." Se tutto nasce da lì, dobbiamo capire in ogni dettaglio quel momento cruciale, ricostruirlo fotogramma per fotogramma, al rallentatore e da diverse angolature. Per questo al Cern di Ginevra è stato realizzato Lhc, l'acceleratore di particelle più potente del mondo, il posto più simile al primo istante di vita dell'universo che l'uomo sia stato in grado di costruire. Per questo da anni i migliori fisici del mondo lavorano giorno...

  6. Inwentarz fary chełmińskiej i jej biblioteki z XV wieku

    Directory of Open Access Journals (Sweden)

    Mateusz Superczyński

    2017-07-01

    Full Text Available Artykuł niniejszy prezentuje edycję nieznanego szerzej dotychczas inwentarza fary chełmińskiej i wykazu księgozbioru biblioteki farnej z XV w., które znajdują się w księdze miejskiej Chełmna – kopiariuszu przywilejów i dokumentów, założonej przez pisarza Konrada Bitschina w 1431 r. Przekaz źródłowy daje obraz biblioteki fary chełmińskiej jako ośrodka kultury w XV-wiecznym Chełmnie. Pozwala także na porównanie trzech zachowanych spisów księgozbiorów średniowiecznego Chełmna, a więc z klasztoru Franciszkanów z XIII wieku, biblioteki farnej i zrekonstruowanego spisu biblioteki Braci Wspólnego Życia z końca XV stulecia, które pochodzą z różnych okresów i odzwierciedlają przemiany w duchowości, teologii i zainteresowaniach naukowych ówczesnych elit intelektualnych miasta. Podczas gdy księgozbiory biblioteki franciszkanów czy farnej oddają ducha średniowiecznej scholastyki czy nominalizmu, to wydania, które posiadali Bracia Wspólnego Życia, zwiastują nadejście humanizmu. Odnotowane przez pisarza miejskiego tytuły, mimo zniekształceń,pozwalają także na identyfikację i odnalezienie wśród nich fundamentalnych dla średniowiecznej teologii, liturgii, historii i filozofii dzieł.

  7. Sulle ipotesi che stanno alla base della geometria e altri scritti scientifici e filosofici

    CERN Document Server

    Riemann, Bernhard

    1994-01-01

    Il volume raccoglie, oltre al testo della lezione del 1854 che dà il titolo all'opera, alcuni scritti di carattere scientifico e filosofico di Riemann. A saggi di argomento scientifico si affiancano scritti di argomento più direttamente metodologico. La concezione della scienza che ci viene offerta da questi scritti è assai significativa del personaggio e della sua epoca. Per Riemann la matematica non è un mero strumento esteriore da applicare, appunto dall'esterno, ai fenomeni. Al contrario, essa consente di spingersi con il rigore necessario oltre alla superficie dei fenomeni e di penetrare sempre più a fondo nella realtà, nell'ottica di un sistema unitario e quasi metafisico del sapere scientifico.

  8. Dicty_cDB: CHE187 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available Homology vs CSM-cDNA Score E Sequences producing significant alignments: (bits) Value CHE187 (CHE187Q) /...4 Homology vs DNA Score E Sequences producing significant alignments: (bits) Value N AB121061 |AB121061...Homology vs Protein Score E Sequences producing significant alignments: (bits) Value U82513_1( U82513 |pid:none)

  9. Dicty_cDB: CHE389 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available CH (Link to library) CHE389 (Link to dictyBase) - - - Contig-U16368-1 - (Link to Original site) - - CHE389Z...CHE389Z 366 - - - - Show CHE389 Library CH (Link to library) Clone ID CHE389 (Link to dictyBase) Atlas...|CK260147.1 EST706225 potato abiotic stress cDNA library Solanum tuberosum cDNA clone POAB268 5' end, mRNA...|CK269700.1 EST715778 potato abiotic stress cDNA library Solanum tuberosum cDNA clone POACO48 3' end, mRNA...|CK261537.1 EST707615 potato abiotic stress cDNA library Solanum tuberosum cDNA clone POABA55 5' end, mRNA

  10. The structures of T87I phosphono-CheY and T87I/Y106W phosphono-CheY help to explain their binding affinities to the FliM and CheZ peptides

    Energy Technology Data Exchange (ETDEWEB)

    McAdams, Kenneth; Casper, Eric S.; Haas, R. Matthew; Santarsiero, Bernard D.; Eggler, Aimee L.; Mesecar, Andrew; Halkides, Christopher J. (UNC); (UIC)

    2008-12-01

    CheY is a response regulator in bacterial chemotaxis. Escherichia coli CheY mutants T87I and T87I/Y106W CheY are phosphorylatable on Asp57 but unable to generate clockwise rotation of the flagella. To understand this phenotype in terms of structure, stable analogs of the two CheY-P mutants were synthesized: T87I phosphono-CheY and T87I phosphono-CheY. Dissociation constants for peptides derived from flagellar motor protein FliM and phosphatase CheZ were determined for phosphono-CheY and the two mutants. The peptides bind phosphono-CheY almost as strongly as CheY-P; however, they do not bind T87I phosphono-CheY or T87I/Y106W phosphono-CheY, implying that the mutant proteins cannot bind FliM or CheZ tightly in vivo. The structures of T87I phosphono-CheY and T87I/Y106W phosphono-CheY were solved to resolutions of 1.8 and 2.4 {angstrom}, respectively. The increased bulk of I87 forces the side-chain of Y106 or W106, into a more solvent-accessible conformation, which occludes the peptide-binding site.

  11. Kui Che on reklaami(kunsti) ikooniks / Andres Laasik

    Index Scriptorium Estoniae

    Laasik, Andres, 1960-2016

    1999-01-01

    Eestis tehtud reklaamid on kahtlaselt sarnased välismaistega. Saksa ajakirjas "Spiegel" oleva ameerika fotoaparaadi Leica reklaam, millel on Che Guevara nägu, on sarnane internetikaubamaja "Osta" reklaamiga.

  12. An Insight into the Interaction Mode Between CheB and Chemoreceptor from Two Crystal Structures of CheB Methylesterase Catalytic Domain

    Energy Technology Data Exchange (ETDEWEB)

    K Cho; B Crane; S Park

    2011-12-31

    We have determined 2.2 {angstrom} resolution crystal structure of Thermotoga maritima CheB methylesterase domain to provide insight into the interaction mode between CheB and chemoreceptors. T. maritima CheB methylesterase domain has identical topology of a modified doubly-wound {alpha}/{beta} fold that was observed from the previously reported Salmonella typhimurium counterpart, but the analysis of the electrostatic potential surface near the catalytic triad indicated considerable charge distribution difference. As the CheB demethylation consensus sites of the chemoreceptors, the CheB substrate, are not uniquely conserved between T. maritima and S. typhimurium, such surfaces with differing electrostatic properties may reflect CheB regions that mediate protein-protein interaction. Via the computational docking of the two T. maritima and S. typhimurium CheB structures to the respective T. maritima and Escherichia coli chemoreceptors, we propose a CheB:chemoreceptor interaction mode.

  13. Conformational barrier of CheY3 and inability of CheY4 to bind FliM control the flagellar motor action in Vibrio cholerae.

    Science.gov (United States)

    Biswas, Maitree; Dey, Sanjay; Khamrui, Susmita; Sen, Udayaditya; Dasgupta, Jhimli

    2013-01-01

    Vibrio cholerae contains multiple copies of chemotaxis response regulator (VcCheY1-VcCheY4) whose functions are elusive yet. Although previous studies suggested that only VcCheY3 directly switches the flagellar rotation, the involvement of VcCheY4 in chemotaxis could not be ruled out. None of these studies, however, focused on the structure, mechanism of activation or molecular basis of FliM binding of the VcCheYs. From the crystal structures of Ca(2+) and Mg(2+) bound VcCheY3 we proposed the presence of a conformational barrier composed of the hydrophobic packing of W61, M88 and V106 and a unique hydrogen bond between T90 and Q97 in VcCheY3. Lesser fluorescence quenching and higher Km value of VcCheY3, compared to its mutants VcCheY3-Q97A and VcCheY3-Q97A/E100A supported our proposition. Furthermore, aforesaid biochemical data, in conjunction with the structure of VcCheY3-Q97A, indicated that the coupling of T90 and Q97 restricts the movement of T90 toward the active site reducing the stabilization of the bound phosphate and effectively promoting autodephosphorylation of VcCheY3. The structure of BeF3(-) activated VcCheY3 insisted us to argue that elevated temperature and/or adequacy of phosphate pool might break the barrier of the free-state VcCheY3 and the conformational changes, required for FliM binding, occur upon phosphorylation. Structure of VcCheY4 has been solved in the free and sulfated states. VcCheY4(sulf), containing a bound sulfate at the active site, appears to be more compact and stable with a longer α4 helix, shorter β4α4 loop and hydrogen bond between T82 and the sulfate compared to VcCheY4(free). While pull down assay of VcCheYs with VcFliMNM showed that only activated VcCheY3 can interact with VcFliMNM and VcCheY4 cannot, a knowledge based docking explained the molecular mechanism of the interactions between VcCheY3 and VcFliM and identified the limitations of VcCheY4 to interact with VcFliM even in its phosphorylated state.

  14. Conformational barrier of CheY3 and inability of CheY4 to bind FliM control the flagellar motor action in Vibrio cholerae.

    Directory of Open Access Journals (Sweden)

    Maitree Biswas

    Full Text Available Vibrio cholerae contains multiple copies of chemotaxis response regulator (VcCheY1-VcCheY4 whose functions are elusive yet. Although previous studies suggested that only VcCheY3 directly switches the flagellar rotation, the involvement of VcCheY4 in chemotaxis could not be ruled out. None of these studies, however, focused on the structure, mechanism of activation or molecular basis of FliM binding of the VcCheYs. From the crystal structures of Ca(2+ and Mg(2+ bound VcCheY3 we proposed the presence of a conformational barrier composed of the hydrophobic packing of W61, M88 and V106 and a unique hydrogen bond between T90 and Q97 in VcCheY3. Lesser fluorescence quenching and higher Km value of VcCheY3, compared to its mutants VcCheY3-Q97A and VcCheY3-Q97A/E100A supported our proposition. Furthermore, aforesaid biochemical data, in conjunction with the structure of VcCheY3-Q97A, indicated that the coupling of T90 and Q97 restricts the movement of T90 toward the active site reducing the stabilization of the bound phosphate and effectively promoting autodephosphorylation of VcCheY3. The structure of BeF3(- activated VcCheY3 insisted us to argue that elevated temperature and/or adequacy of phosphate pool might break the barrier of the free-state VcCheY3 and the conformational changes, required for FliM binding, occur upon phosphorylation. Structure of VcCheY4 has been solved in the free and sulfated states. VcCheY4(sulf, containing a bound sulfate at the active site, appears to be more compact and stable with a longer α4 helix, shorter β4α4 loop and hydrogen bond between T82 and the sulfate compared to VcCheY4(free. While pull down assay of VcCheYs with VcFliMNM showed that only activated VcCheY3 can interact with VcFliMNM and VcCheY4 cannot, a knowledge based docking explained the molecular mechanism of the interactions between VcCheY3 and VcFliM and identified the limitations of VcCheY4 to interact with VcFliM even in its phosphorylated state.

  15. CheMin Instrument Performance and Calibration on Mars

    Science.gov (United States)

    Vaniman, D. T.; Blake, D. F.; Morookian, J. M.; Yen, A. S.; Ming, D. W.; Morris, R. V.; Achilles, C. N.; Bish, D. L.; Chipera, S. J.; Morrison, S. M.; hide

    2013-01-01

    The CheMin (Chemistry and Mineralogy) instrument on the Mars Science Laboratory rover Curiosity uses a CCD detector and a Co-anode X-ray tube source to acquire both mineralogy (from the pattern of Co diffraction) and chemical information (from energies of fluoresced X-rays). A key component of the CheMin instrument is the ability to move grains within sample cells during analysis, providing multiple, random grain orientations that disperse diffracted X-ray photons along Debye rings rather than producing discrete Laue spots. This movement is accomplished by piezoelectric vibration of the sample cells. A cryocooler is used to maintain the CCD at a temperature at about -50 C in order to obtain energy resolution better than 250 eV, allowing discrimination of diffracted Co K X-rays from Fe K and other fluorescent X-rays. A detailed description of CheMin is provided in [1]. The CheMin flight model (FM) is mounted within the body of Curiosity and has been operating on Mars since August 6, 2012. An essentially identical sister instrument, the CheMin demonstration model (DM), is operated in a Mars environment chamber at JPL.

  16. Ragioni e vantaggi del classificare la musica

    Directory of Open Access Journals (Sweden)

    Filippo Focosi

    2012-05-01

    Full Text Available The contemporary music scene, imbued with stylistic contaminations, is dominated by the idea that the differentiation between musical genres no longer makes sense: the only legitimate distinction should be between good and bad music. Yet, the so mistreated labels that separate classical music from jazz and pop are still in use, both in critical discourse and in the organization of musical life, individual and collective. In the attempt to solve this apparent paradox, which closely resembles the paradox of taste that animated the philosophical debate in Britain in the eighteenth century, the essay points out the advantages (as well as the limitations inherent to the genre conventions, also relating them to postmodern musical culture.

  17. Data from the Mars Science Laboratory CheMin XRD/XRF instrument

    Science.gov (United States)

    Vaniman, David; Bristow, , David Blake, Tom; Des Marais, David; Achilles, Cherie; Spanovich, Ashwin Vasavada, , Robert Anderson, Joy Crisp, John Michael Morookian, Nicole; Yen, Albert; Bish, David; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Farmer, Jack; Grotzinger, John; Stolper, Edward; Morris, , Douglas Ming, Richard; Rampe, Elizabeth; Treiman, Allan; Sarrazin, Philippe; MSL Science Team

    2013-04-01

    The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity uses a Co tube source and a CCD detector to acquire mineralogy from diffracted primary X-rays and chemical information from fluoresced X-rays. CheMin has been operating at the MSL Gale Crater field site since August 5, 2012 and has provided the first X-ray diffraction (XRD) analyses in situ on a body beyond Earth. Data from the first sample collected, the Rocknest eolian soil, identify a basaltic mineral suite, predominantly plagioclase (~An50), forsteritic olivine (~Fo58), augite and pigeonite, consistent with expectation that detrital grains on Mars would reflect widespread basaltic sources. Minor phases (each allophane or hisingerite. Constraints from phase chemistry of the crystalline components, compared with a Rocknest bulk composition from the APXS instrument on Curiosity, indicate that in sum the amorphous or poorly crystalline components are relatively Si, Al, Mg-poor and enriched in Ti, Cr, Fe, K, P, S, and Cl. All of the identified crystalline phases are volatile-free; H2O, SO2 and CO2 volatile releases from a split of this sample analyzed by the SAM instrument on Curiosity are associated with the amorphous or poorly ordered materials. The Rocknest eolian soil may be a mixture of local detritus, mostly crystalline, with a regional or global set of dominantly amorphous or poorly ordered components. The Rocknest sample was targeted by MSL for "first time analysis" to demonstrate that a loose deposit could be scooped, sieved to <150 µm, and delivered to instruments in the body of the rover. A drilled sample of sediment in outcrop is anticipated. At the time of writing this abstract, promising outcrops are in range and this talk will provide an update on data collected with the CheMin instrument.

  18. Che cos'è la vita ?, Scienza e umanesimo

    CERN Document Server

    Schrödinger, Erwin

    1988-01-01

    A cento anni dalla nascita di Erwin Schrödinger (Viena 1887), il suo pensiero e il suo lavoro mantengono inalterati la loro attualità, come dimostra la nuova pubblicazione di molti dei suoi testi e i numerosi convegni che gli vengono dedicati.

  19. à l'encoche sèche

    African Journals Online (AJOL)

    encoche sèche chez Hevea brasiliensis. 3. Résultats. Les longueurs d'encoche malades (LEM) des. 13 clones soumis aux huit traitements pendant les cinq premières années d'exploitation sont présentées dans le tableau 2. L'analyse de variance ...

  20. Crèche and School - Important dates

    CERN Multimedia

    Staff Association

    2018-01-01

    Enrolments 2018-2019 Enrolments to the Crèche and School for the school year 2018-2019 will take place on 5, 6 and 7 March 2018 from 10 am to 1 pm at the Crèche and School of the CERN Staff Association. Registration forms will be available from Thursday 1st March 2018. For more information, please visit the website: http://nurseryschool.web.cern.ch/. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Saturday 3 March 2018 Open Day at Crèche and School of the CERN Staff Association Are you considering enrolling your child to the Crèche and School of the CERN Staff Association? If you work at CERN, then this event is for you: come visit the school and meet the Management on Saturday 3 March 2018 from 10 to 12 am It will be our pleasure to present to you our structure, its projects and premises, and answer any questions you may have. Please sign up for one of the two sessions via Doodle before Friday 2 March 2018: htt...

  1. A crèche on the Meyrin CERN site

    CERN Multimedia

    Association du personnel

    2013-01-01

    A few months ago (see Echo 175) we announced the opening, at the end of August, of a crèche at the CERN Staff Association’s nursery school. After a very active summer, where a new floor was added to the canteen building, the new school year started in excellent conditions and, as expected, the new crèche opened on Tuesday 27 August. This crèche, with 13 full-time equivalent places, can accept 18 children aged between three months and two years in a space fully refitted to care for the little ones. A specially designed space for breastfeeding helps mothers working on the site to respect their baby's rhythm. In compliance with the standards of supervision in the canton of Geneva six educators take care of the children in shifts. This new space is fully integrated in the nursery school so that now the crèche, Kindergarten and school of the CERN Staff Association can welcome children aged from three months to six years, from Monday to Friday, and...

  2. La cultura che verrà. La comunicazione visiva come strumento trasparente, per un libero accesso a risorse e saperi

    Directory of Open Access Journals (Sweden)

    Enrico Parisio

    2011-12-01

    Full Text Available Oggi gli apparati tecnologico/comunicativi si garantiscono l’autosufficienza: la diffusione dei messaggi utilizza come “nodi” di propagazione noi stessi, gli utenti. Sono gli apparati che ci impiegano, non siamo noi ad utilizzarli. La  funzione progettuale, deve essere inserita in un contesto totalmente capovolto rispetto al passato: come progettisti dobbiamo favorire fondamentalmente il flusso di informazioni, del tutto eterodiretto. Lasciar accadere è la parola d’ordine, senza alcuna intenzionalità “rappresentativa”. Il soggetto autoritario viene sostituito dalla terza persona, dall’impersonalità degli eventi che incedono, dalle molteplicità, dai soggetti collettivi. L’autore oggi di un progetto è un non autore, un non soggetto, un “egli”. Il progetto di comunicazione visiva deve confrontarsi oggi non solo con i nuovi linguaggi della tecnologia, ma soprattutto con quelli ben più complessi che i soggetti reali attivano sperimentando nuove forme di socialità, di aggregazione, di conflitto.

  3. Profili penali della disciplina dei gruppi di società

    OpenAIRE

    Fiorella, Michele

    2012-01-01

    Mediante l’inserimento, all’interno della fattispecie di infedeltà patrimoniale, della previsione normativa dei vantaggi compensativi la tematica dei gruppi di società ha ricevuto una dignità espressa anche nel settore del diritto penale dell’economia. La scelta di politica legislativa, che si inserisce più genericamente nell’obiettivo politico criminale del legislatore novellante di costruire un diritto penale societario minimo, permeato dal necessario rispetto dei canoni di concreta offe...

  4. Care and education in the Danish Créche

    DEFF Research Database (Denmark)

    Broström, Stig; Hansen, Ole Henrik

    2010-01-01

    This article seeks to identify the relation between policy and lived life, for the small child in the Danish crèche. To accomplish this, the article integrates demography, traditions, national curriculum and psychological, educational, and recent developments in research. It is an attempt to reveal...... research articles. It is used in the exploration of meanings of political, social, and cultural phenomena as experienced by the involved individuals themselves, in their natural context. It is a presumption that the child’s development is a consequence of emotional and cognitive stimulation. To outline...... that, it is vital to emphasize the influence that policy causes on educational practice in the crèche, e.g., the conceptualization of education and care....

  5. Le Saix – Barnèche 2

    OpenAIRE

    Morin, Alexandre

    2013-01-01

    Identifiant de l'opération archéologique : 8223 Date de l'opération : 2007 (SD) Le site de Barnèche 2 est implanté à 847 m d’altitude dans la petite vallée du torrent de Barnèche, affluent du torrent de la Maraize, sur la commune du Saix. Ce site, découvert par Henri Faure, a fourni lors des ramassages de surface plusieurs centaines de pièces, essentiellement des silex taillés, se rapportant à des ambiances chronoculturelles néolithiques. La cartographie des ramassages montre que le site s’ét...

  6. Pragmatic idealism: Ernesto "Che" Guevara's strategic choice for Bolivia

    OpenAIRE

    Wise, Philip E.

    2017-01-01

    Approved for public release; distribution is unlimited Throughout history there are political and military decisions that appear, on the surface, to have been made without a proper assessment of the situation they are meant to address. These decisions are sometimes discounted as wrongheaded or foolish. Ernesto Che Guevara's decision to fight a guerrilla war in Bolivia is one such event. Focus on the failure of Guevara's Bolivian mission and his subsequent death at the hands of the Bolivian...

  7. Capitolo IV. Che cos’è la storia? L’archeologia e la statistica

    OpenAIRE

    Tarde, Gabriel

    2016-01-01

    Che cos’è la storia? È questa la prima domanda alla quale dobbiamo rispondere? Siamo portati a farlo nel modo più naturale, e a formulare le leggi dell’imitazione occupandoci di due tipi di ricerche molto diverse che il nostro tempo ha posto in grande onore, gli studi archeologici e gli studi statistici. Mostrerò che essi tendono inconsciamente, man mano che progrediscono, a esaminare i fenomeni sociali da un punto di vista simile al nostro, e che, a questo proposito, i risultati generali, i ...

  8. Cloning and expression of Che a 1, the major allergen of Chenopodium album in Escherichia coli.

    Science.gov (United States)

    Vahedi, Fatemeh; Sankian, Mojtaba; Moghadam, Malihe; Mohaddesfar, Maryam; Ghobadi, Sirous; Varasteh, Abdol Reza

    2011-04-01

    Chenopodium album is a weedy annual plant in the genus Chenopodium. C. album pollen represents a predominant allergen source in Iran. The main C. album pollen allergens have been described as Che a 1, Che a 2, and Che a 3. The aim of this work was to clone the Che a 1 in Escherichia coli to establish a system for overproduction of the recombinant Che a 1 (rChe a 1). In order to clone this allergen, the pollens were subjected to RNA extraction. A full-length fragment encoding Che a 1 was prepared by polymerase chain reaction amplification of the first-strand cDNA synthesized from extracted RNA. Cloning was carried out by inserting the cDNA into the pET21b+ vector, thereafter the construct was transformed into E. coli Top10 cells and expression of the protein was induced by IPTG. The rChe a 1 was purified using histidine tag in recombinant protein by means of Ni-NTA affinity chromatography. IgE immunoblotting, ELISA, and inhibition ELISA were done to evaluate IgE binding of the purified protein. In conclusion, the cDNA for the major allergen of the C. album pollen, Che a 1, was successfully cloned and rChe a 1 was purified. Inhibition assays demonstrated allergic subjects sera reacted with rChe a 1 similar to natural Che a 1 in crude extract of C. album pollen. This study is the first report of using the E. coli as a prokaryotic system for Che a 1 cloning and production of rChe a 1.

  9. Data from the Mars Science Laboratory CheMin XRD/XRF Instrument

    Science.gov (United States)

    Vaniman, David; Blake, David; Bristow, Tom; DesMarais, David; Achilles, Cherie; Anderson, Robert; Crips, Joy; Morookian, John Michael; Spanovich, Nicole; Vasavada, Ashwin; hide

    2013-01-01

    The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity uses a Co tube source and a CCD detector to acquire mineralogy from diffracted primary X-rays and chemical information from fluoresced X-rays. CheMin has been operating at the MSL Gale Crater field site since August 5, 2012 and has provided the first X-ray diffraction (XRD) analyses in situ on a body beyond Earth. Data from the first sample collected, the Rocknest eolian soil, identify a basaltic mineral suite, predominantly plagioclase (approx.An50), forsteritic olivine (approx.Fo58), augite and pigeonite, consistent with expectation that detrital grains on Mars would reflect widespread basaltic sources. Minor phases (each <2 wt% of the crystalline component) include sanidine, magnetite, quartz, anhydrite, hematite and ilmenite. Significantly, about a third of the sample is amorphous or poorly ordered in XRD. This amorphous component is attested to by a broad rise in background centered at approx.27deg 2(theta) (Co K(alpha)) and may include volcanic glass, impact glass, and poorly crystalline phases including iron oxyhydroxides; a rise at lower 2(theta) may indicate allophane or hisingerite. Constraints from phase chemistry of the crystalline components, compared with a Rocknest bulk composition from the APXS instrument on Curiosity, indicate that in sum the amorphous or poorly crystalline components are relatively Si, Al, Mg-poor and enriched in Ti, Cr, Fe, K, P, S, and Cl. All of the identified crystalline phases are volatile-free; H2O, SO2 and CO2 volatile releases from a split of this sample analyzed by the SAM instrument on Curiosity are associated with the amorphous or poorly ordered materials. The Rocknest eolian soil may be a mixture of local detritus, mostly crystalline, with a regional or global set of dominantly amorphous or poorly ordered components. The Rocknest sample was targeted by MSL for "first time analysis" to demonstrate that a loose deposit could be scooped, sieved to

  10. Il mondo secondo la fisica quantistica segreti e meraviglie della scienza che sta cambiando la nostra vita

    CERN Document Server

    Fracas, Fabio

    2017-01-01

    Questo libro è un'avventura esclusiva e affascinante. Un viaggio, anche nel tempo, alla scoperta di qualcosa di nuovo e di straordinario: la Fisica Quantistica, nelle sue logiche, nelle sue potenzialità, nelle sue applicazioni e nei suoi possibili sviluppi. All'interno del volume vengono ricostruiti passo dopo passo i momenti fondamentali del pensiero quantistico, le questioni su cui si sono interrogati i più grandi scienziati degli ultimi decenni, e i diversi contesti nei quali si sono evoluti i principali modelli della Meccanica Quantistica. Sullo sfondo delle ricerche più attuali - come per esempio quella sulle onde gravitazionali che ha portato al Nobel per la Fisica 2017 -, vengono indagati anche i rapporti esistenti fra Fisica Quantistica, Relatività Einsteiniana e Teoria delle Stringhe. Inoltre, fra i tanti temi trattati nelle sue pagine, trovano spazio persino le incredibili ricadute che gli studi sulla Fisica Quantistica stanno avendo negli ambiti della medicina e delle ricerche sul cervello e s...

  11. Finally, a crèche at CERN!

    CERN Multimedia

    Anaïs Schaeffer

    2013-01-01

    After many years of discussion, the CERN Staff Association’s first crèche will open its doors in September to welcome up to 20 babies and toddlers.   A delicate operation: the installation of 11 modules above the Nursery's School canteen. Image: Sigrid Knoops. The CERN Staff Association’s Nursery School, which will soon turn 50, is pleased to announce the establishment of CERN’s first crèche. This project, which has come to fruition over the past academic year with the support of the CERN Management, meets an established and growing need among the Laboratory’s personnel and users. As a modular construction, the Nursery School’s new second floor was assembled above the existing canteen in a matter of days. Its 11 modules are ultra-modern – they’re even equipped with underfloor heating. “Thanks to this extension, we will be able to accept around twenty babies at the start of the academ...

  12. Action at a distance: amino acid substitutions that affect binding of the phosphorylated CheY response regulator and catalysis of dephosphorylation can be far from the CheZ phosphatase active site.

    Science.gov (United States)

    Freeman, Ashalla M; Mole, Beth M; Silversmith, Ruth E; Bourret, Robert B

    2011-09-01

    Two-component regulatory systems, in which phosphorylation controls the activity of a response regulator protein, provide signal transduction in bacteria. For example, the phosphorylated CheY response regulator (CheYp) controls swimming behavior. In Escherichia coli, the chemotaxis phosphatase CheZ stimulates the dephosphorylation of CheYp. CheYp apparently binds first to the C terminus of CheZ and then binds to the active site where dephosphorylation occurs. The phosphatase activity of the CheZ(2) dimer exhibits a positively cooperative dependence on CheYp concentration, apparently because the binding of the first CheYp to CheZ(2) is inhibited compared to the binding of the second CheYp. Thus, CheZ phosphatase activity is reduced at low CheYp concentrations. The CheZ21IT gain-of-function substitution, located far from either the CheZ active site or C-terminal CheY binding site, enhances CheYp binding and abolishes cooperativity. To further explore mechanisms regulating CheZ activity, we isolated 10 intragenic suppressor mutations of cheZ21IT that restored chemotaxis. The suppressor substitutions were located along the central portion of CheZ and were not allele specific. Five suppressor mutants tested biochemically diminished the binding of CheYp and/or the catalysis of dephosphorylation, even when the suppressor substitutions were distant from the active site. One suppressor mutant also restored cooperativity to CheZ21IT. Consideration of results from this and previous studies suggests that the binding of CheYp to the CheZ active site (not to the C terminus) is rate limiting and leads to cooperative phosphatase activity. Furthermore, amino acid substitutions distant from the active site can affect CheZ catalytic activity and CheYp binding, perhaps via the propagation of structural or dynamic perturbations through a helical bundle. Copyright © 2011, American Society for Microbiology. All Rights Reserved.

  13. Solu che fera: New and Old Silences in the Work Experience of the Sardinian Shepherds

    Directory of Open Access Journals (Sweden)

    Claudia Guendalina Sias

    2015-07-01

    Full Text Available L’articolo prende le mosse da una ricerca etnografica conclusa nel 2012 che ha avuto per oggetto l’immigrazione albanese nel contesto agropastorale della Sardegna. Obiettivo dell’articolo è analizzare il nesso che lega solitudine e pastorizia, topos mitico e poetico della condizioni del pastore in generale, che trova una specifica declinazione nella condizione degli immigrati albanesi impiegati nelle aziende sarde come dipendenti o “servi-pastori”.

  14. Che in Santiago de Cuba. His Universidad de Oriente visit

    Directory of Open Access Journals (Sweden)

    Yolanda Corujo-Vallejo

    2016-09-01

    Full Text Available Ernesto Che Guevara begins his activity in the process of the Cuban Revolution since 1955, stamped by the meeting with Fidel Castro in Mexico. After the triumph, transformed in one of the Revolution´s Commandants for his distinguished attitude, develops a multifaceted and creative activity, in the process of the construction of the new society. For that reason, between 1959 and 1964, in some opportunities he visits the city of Santiago of Cuba. His presence is also felt in the University of Oriente, where he comes on his first visit to the city, checks the construction of the university city, interchanges with students and teachers about the relevance of the application of the scientific knowledge in the development of the new society.

  15. Rachunek dochodów i wydatków budżetu jednostki samorządu terytorialnego na przykładzie gminy Chełmiec w latach 2011-2013

    OpenAIRE

    Rodak, Anna

    2015-01-01

    Przedłożona praca ma na celu wskazanie źródeł i struktury dochodów budżetowych oraz charakteru wydatkowania środków budżetowych gminy Chełmiec, a także dokonanie rzetelnej oceny sytuacji finansowej wymienionej powyżej jednostki. Analiza budżetu obejmuje zakres czasowy od 2011 do 2013 roku. Szczegółowe pytania, na które starano się w niniejszej pracy odpowiedzieć są następujące: Czy gmina Chełmiec jest gospodarna w wykorzystywaniu środków budżetowych? oraz jak gmina Chełmiec mając do dyspozycj...

  16. Le avventure della canzone italiana tra lingua che si consuma e ...

    African Journals Online (AJOL)

    This article analyses the Italian popular song between the 30s and the 90s of the past century, with special attention to its most significant developments, very insightful in this case, in order to understand the country's social and cultural changes and to see how the language of popular songs played an educational role in ...

  17. Discovering Che-1/AATF: a new attractive target for cancer therapy

    Directory of Open Access Journals (Sweden)

    Simona eIezzi

    2015-04-01

    Full Text Available The transcriptional cofactor Che-1/AATF is currently emerging as an important component of the DNA damage response machinery, the complex signaling network that maintains genome integrity and prevents tumorigenesis. Moreover this protein is involved in a wide range of cellular pathways, regulating proliferation and survival in both physiological and pathological conditions. Notably, some evidence indicates that dysregulation of Che-1/AATF levels are associated with the transformation process and elevated levels of Che-1/AATF are required for tumor cell survival. It is for these reasons that Che-1/AATF has been regarded as an attractive, still theoretical, therapeutic target for cancer treatments. In this review, we will provide an updated overview of Che-1/AATF activities, from transcriptional regulation to DNA damage response.

  18. Che cosa (non è rimasto della francesità?: addomesticamento e straniamento nelle traduzioni italiana e slovena di Les fleurs bleues di Raymond Queneau

    Directory of Open Access Journals (Sweden)

    Martina Ožbot

    2013-12-01

    Full Text Available Nel presente contributo vengono offerte alcune riflessioni sulla traduzione di aspetti culturalmente specifici nel testo letterario, e in particolare sulle versioni italiana e slovena del romanzo Les Fleurs bleues di Raymond Queneau, che sono opera rispettivamente di Italo Calvino e di Ana Barič Moder. Al centro dellʼattenzione è soprattutto la dicotomia traduttiva tra lʼapproccio straniante e quello domesticante. Un esame del testo originale e delle due traduzioni ha dimostrato che ambedue i traduttori si sono sforzati di preservare i caratteri della cultura di partenza iscritti nel romanzo queneauiano. Allo stesso tempo, però, hanno cercato di integrare le proprie versioni negli ambienti dʼarrivo quando ciò pareva necessario per rendere possibile il pieno funzionamento delle due traduzioni come opere letterarie che, nei specifici contesti italiano e sloveno, sono destinate ad avere la funzione di entità letterarie a sé stanti, cioè indipendenti dal loro primario legame con il testo di partenza francese. Fatte queste premesse, lʼapproccio generale dei due traduttori può essere caratterizzato come relativamente addomesticante, anche se in entrambe le versioni, e in particolare in quella italiana, viene concesso ampio spazio anche allo straniamento, purché esso non incrini la funzionalità della traduzione.

  19. Che cos'è la conoscenza? un universo in espansione

    CERN Document Server

    Franceschini, Guiliano

    2017-01-01

    Il testo propone un viaggio nell'universo della conoscenza, tra le galassie di conoscenza (religione, scienza, arte), nel cervello (percezione, apprendimento, memoria) e nell'etica (dalla conoscenza all'educazione). Le argomentazioni si espandono attraverso un registro comunicativo intuitivo, tra divulgazione e speculazione, attraverso esempi e riferimenti concreti, rivolgendosi in alcuni casi direttamente al lettore.

  20. MSL Chemistry and Mineralogy X-Ray Diffraction X-Ray Fluorescence (CheMin) Instrument

    Science.gov (United States)

    Zimmerman, Wayne; Blake, Dave; Harris, William; Morookian, John Michael; Randall, Dave; Reder, Leonard J.; Sarrazin, Phillipe

    2013-01-01

    This paper provides an overview of the Mars Science Laboratory (MSL) Chemistry and Mineralogy Xray Diffraction (XRD), X-ray Fluorescence (XRF) (CheMin) Instrument, an element of the landed Curiosity rover payload, which landed on Mars in August of 2012. The scientific goal of the MSL mission is to explore and quantitatively assess regions in Gale Crater as a potential habitat for life - past or present. The CheMin instrument will receive Martian rock and soil samples from the MSL Sample Acquisition/Sample Processing and Handling (SA/SPaH) system, and process it utilizing X-Ray spectroscopy methods to determine mineral composition. The Chemin instrument will analyze Martian soil and rocks to enable scientists to investigate geophysical processes occurring on Mars. The CheMin science objectives and proposed surface operations are described along with the CheMin hardware with an emphasis on the system engineering challenges associated with developing such a complex instrument.

  1. Stealing or Steeling the Image? The Failed Branding of the Guerrillero Heroico image of Che Guevara

    National Research Council Canada - National Science Library

    Maria-Carolina Cambre

    2012-01-01

    ... Korda’s famous image of Che Guevara, The Guerrillero Heroico, as a brand, trademark or logo, and those who insist it is a political/cultural icon and non-commercial and that these categories are mutually exclusive...

  2. Rumors: A un tale je arisurta che a Roma, all'unnici de maggio...

    OpenAIRE

    Crescimebene, Massimo; La Longa, Federica

    2011-01-01

    Il presente lavoro parla, con taglio scientifico leggero, di dicerie, chiacchiere, bufale e leggende metropolitane. La psicologia sociale, più elegantemente, le definisce rumor (rumour in inglese britannico), utilizzando la parola latina che significa appunto rumore, voce, diceria, pettegolezzo. I rumors, nella comunicazione pubblica, economica, politica, scientifica e culturale, indicano una notizia, presumibilmente vera, che circola senza però essere stata confermata o resa evidente. ...

  3. Rumors: A un tale j’arisurta che a Roma, all'unnici de maggio...

    OpenAIRE

    Crescimbene, Massimo

    2011-01-01

    Il presente lavoro parla, con taglio scientifico leggero, di dicerie, chiacchiere, bufale e leggende metropolitane. La psicologia sociale, più elegantemente, le definisce rumor (rumour in inglese britannico), utilizzando la parola latina che significa appunto rumore, voce, diceria, pettegolezzo. I rumors, nella comunicazione pubblica, economica, politica, scientifica e culturale, indicano una notizia, presumibilmente vera, che circola senza però essere stata confermata o resa evidente. ...

  4. L'immagine visibile di un Dio che può essere: Michel Henry e Richard Kearney in dialogo

    Directory of Open Access Journals (Sweden)

    Jonah M. Ford

    2015-07-01

    Full Text Available   This article attempts an exploration of Michel Henry’s I Am the Truth and Richard Kearney’s The God Who May Be, as each appropriate the Husserlian critique of Kantian epistemology. Although Henry and Kearney both develop a Christian theology rooted in this Husserlian inheritance, their explication of the truths Christianity asserts is strikingly different. It is the assertion of this essay that this difference is primarily a textual one; or, to put it another way, it is conditioned first by their scriptural gaze.Cet article se propose de reprendre le contenu de Michel Henry, C’est moi, la vérité et Richard Kearney The God Who May Be, dans lesquels les auteurs analysent la critique husserlienne de l’épistémologie kantienne. Bien que Henry et Kearney tous les deux développent une théologie chrétienne enracinée dans cet héritage husserlien, leur explication des vérités affirmées du Christianisme est très différente. Pour nous, la différence entre eux est de type textuel, c’est à dire qu’elle dépend de l’analyse qu’ils font de la Sainte Écriture.Questo articolo si propone di riprendere il contenuto dei testi Io sono la verità di Michel Henry e The God Who May Be di Richard Kearney, nei quali i rispettivi autori analizzano la critica husserliana dell'epistemologia di Kant. Sebbene entrambi sviluppano una "teologia" cristiana radicata in questa eredità husserliana, la loro spiegazione delle verità cristiane è alquanto differente. Per noi, la differenza tra essi è di tipo testuale, vale a dire che dipende dall'analisi che essi fanno del testo biblico.

  5. Nascita e destino della soggettività. Dai ruoli professionali ai processi di cura, attraverso una lettura di "Quel che resta del giorno" di Kazuo Ishiguro

    Directory of Open Access Journals (Sweden)

    Gabriele Profita

    2017-07-01

    Full Text Available Questa riflessione affronta un tema assai rilevante per le professioni di cura, con uno sguardo particolare alla psicoterapia. Per chiarire il ruolo della soggettività e della nascita e maturazione di un ruolo professionale riporterò un’analisi di un testo letterario attraverso il quale sarà più agevole scoprire come si forma l’identità di un ruolo professionale e come si avvia alla sua maturazione e alla sua codificazione. In particolare quali sono i rischi legati ad una sua rigida codificazione rivolta alla sua normatività tecnica? Mi propongo di tracciare un confronto con alcune forme di costruzione della soggettività che nel corso dei secoli hanno fondato il modello dell’uomo occidentale nelle sue articolazioni professionali.

  6. The new Meyrin crèche takes its first steps

    CERN Multimedia

    2008-01-01

    The new Meyrin crèche was inaugurated on 10 October and already caters for 16 children of CERN personnel. Copyright: Laurent Barlier. Copyright: Robert Tillmann. At the end of August, the new Meyrin crèche in Champs-Fréchets, the Espace de Vie Enfantine (EVE), welcomed its first intake of infants. They included 16 children of members of the CERN personnel who are benefiting from the agreement signed in 2007 with the commune of Meyrin (see Bulletin n°43&44/2007). The crèche was officially inaugurated on 10 October with several CERN representatives in attendance, including HR Department Head, Enrico Chiaveri, and Head of the Relations with the Host States Service, Friedmann Eder. The following day, EVE held an open day for the inhabitants of Meyrin and interested members of the CERN personnel. The new 1516 m2 building ‘s spaces have very clean and ...

  7. Il lungo freddo storia di Bruno Pontecorvo, lo scienziato che scelse l'URSS

    CERN Document Server

    Mafai, Miriam

    2012-01-01

    Nelle parole della grande giornalista recentemente scomparsa, la documentata narrazione della storia di Bruno Pontecorvo, fisico nucleare di fama mondiale che, nel pieno della Guerra fredda, scelse di abbandonare l'Occidente e di lavorare e vivere nell'Unione Sovietica. Grazie alla capacità della Mafai nel ricostruire gli eventi cruciali della vita di Pontecorvo in un nuovo quadro rivelatore, "Il lungo freddo" non offre solo un'inedita prospettiva sulla drammatica corsa alla bomba atomica - dalle decisive scoperte del Progetto Manhattan alla tragica esplosione di Hiroshima, dalla prima atomica sovietica alla bomba all'idrogeno - ma rappresenta soprattutto la memoria collettiva di una generazione che ha posto la politica al centro delle proprie scelte di vita. E svela i drammi umani di un conflitto che per più di quarant'anni ha diviso il mondo.

  8. Il rischio tecnologico vantaggi e svantaggi del progresso scientifico

    CERN Document Server

    Lewis, H W

    1995-01-01

    I rischi della vita ; misurare il rischio ; la percezione del rischio ; la politica del rischio ; la valutazione del rischio ; la gestione del rischio ; il valore della vita ; qual è il livello "sufficiente" di sicurezza? ; incertezza, causalità, rilevabilità ; le delusioni della cautela ; sostanze chimiche tossiche ; sostanze chimiche cancerogene ; sicurezza sulle autostrade ; trasporto aereo ; radiazioni ionizzanti ; conbustibili fossili ; l'inverno nucleare ; radiazioni non ionizzanti ; quanto basta di statistica e di teoria delle probabilità ; epilogo : cosa significa tutto questo?.

  9. Crèche and School: Open Day on Saturday, 3 March

    CERN Multimedia

    EVE et École

    2018-01-01

    Open Day at Crèche and School of the CERN Staff Association Are you considering enrolling your child to the Crèche and School of the CERN Staff Association? If you work at CERN, then this event is for you: come visit the school and meet the Management on Saturday 3 March 2018 from 10 to 12 am It will be our pleasure to present to you our structure, its projects and premises, and answer any questions you may have. Please sign up for one of the two sessions via Doodle before Wednesday 28 February 2018: https://doodle.com/poll/3qvrb6m73pktqbft

  10. Abbrüche bei Online-Befragungen : Ergebnisse einer Befragung von Medizinern

    OpenAIRE

    El-Menouar, Yasemin; Blasius, Jörg

    2005-01-01

    Der Beitrag befasst sich mit dem hohen Anteil von Abbrüchen bei Online-Befragungen am Beispiel einer Befragung von Medizinern. Die Abbrüche erfolgen zum einen direkt bei der Kontaktierung, d.h. die zu Befragenden reagieren nicht auf ein zuvor verschicktes Anschreiben bzw. auf eine Aufforderung via Banner oder via Pop-up Fenster. Zum anderen wird häufig die Startseite der Untersuchung aufgerufen, nicht aber der Fragebogen. Die hier interessierenden Abbrüche sind jene, die während der Bearbeitu...

  11. A crèche for CERN staff The Staff Association project

    CERN Multimedia

    Association du personnel

    2006-01-01

    For many years, the Staff Association has supported the demand for the creation of a crèche for the children of CERN staff. Several studies have been carried out without leading to a concrete plan. The fact that the CERN population is getting younger and the shortage of local facilities have led to a more urgent demand for this type of social service over the past few years. Furthermore, the Equal Opportunities Panel had already recommended that crèche places be made available.

  12. Che Guevara: a mídia como potencializadora do mito

    OpenAIRE

    Domingues, Juan de Moraes

    2008-01-01

    Este trabalho analisa a força de permanência do mito de Che Guevara 40 anos depois de sua morte. Desde que foi morto na Bolívia, em outubro de 1967, Che se transformou em mito, a despeito de suas distintas versões e releituras ao longo do tempo. A famosa foto de Alberto Korda, reproduzida aos milhares nessas quatro décadas, se tornou uma espécie de totem ideológico, mas também uma imagem consumida por milhares de pessoas das mais diferentes maneiras. Esta dissertação, portanto, se ocupa em ve...

  13. Dissoziation von Sauerstoffmolekülen auf der Al(111) Oberfläche

    OpenAIRE

    Behler, J.

    2004-01-01

    Die Dissoziation von Sauerstoffmolekülen auf der Al(111) Oberfläche ist eine wichtige Modellreaktion für die Adsorption einfacher Moleküle auf Metalloberflächen. Zahlreiche Experimente haben gezeigt, dass die anfängliche Haftwahrscheinlichkeit thermischer Sauerstoffmoleküle beim Auftreffen auf die Al(111) Oberfläche nur etwa ein Prozent beträgt. Eine einfache Erklärung wäre die Existenz von Energiebarrieren auf dem Dissoziationsweg, die nur von Molekülen höherer kinetischer Energie überwunden...

  14. Switched or not?: the structure of unphosphorylated CheY bound to the N terminus of FliM.

    Science.gov (United States)

    Dyer, Collin M; Dahlquist, Frederick W

    2006-11-01

    Phosphorylation of Escherichia coli CheY increases its affinity for its target, FliM, 20-fold. The interaction between BeF(3)(-)-CheY, a phosphorylated CheY (CheY approximately P) analog, and the FliM sequence that it binds has been described previously in molecular detail. Although the conformation that unphosphorylated CheY adopts in complex with FliM was unknown, some evidence suggested that it is similar to that of CheY approximately P. To resolve the issue, we have solved the crystallographic structure of unphosphorylated, magnesium(II)-bound CheY in complex with a synthetic peptide corresponding to the target region of FliM (the 16 N-terminal residues of FliM [FliM(16)]). While the peptide conformation and binding site are similar to those of the BeF(3)(-)-CheY-FliM(16) complex, the inactive CheY conformation is largely retained in the unphosphorylated Mg(2+)-CheY-FliM(16) complex. Communication between the target binding site and the phosphorylation site, observed previously in biochemical experiments, is enabled by a network of conserved side chain interactions that partially mimic those observed in BeF(3)(-)-activated CheY. This structure makes clear the active role that the beta4-alpha4 loop plays in the Tyr(87)-Tyr(106) coupling mechanism that enables allosteric communication between the phosphorylation site and the target binding surface. Additionally, this structure provides a high-resolution view of an intermediate conformation of a response regulator protein, which had been generally assumed to be two state.

  15. Trent'anni che sconvolsero la fisica la storia della teoria dei quanti

    CERN Document Server

    Gamow, George

    1993-01-01

    Gli anni dal 1900 al 1930 hanno portato un profondo mutamento nella visione che l'uomo aveva dell'universo: tra la prima idea di Max Planck dei quanti di luce nel 1900, e la previsione dell'esistenza delle antiparticelle formulata da P. A. M. Dirac nel 1929, corre un periodo di emozionanti progressi nel campo della fisica teorica.

  16. Writing "Che" Writing: Apocryphal Diaries and the Deconstruction of Guevara's Myth

    Science.gov (United States)

    Weiser, Frans

    2013-01-01

    Ernesto "Che" Guevara's iconic photograph has taken on mythical proportions since his death. Though his image has ironically been exploited by the apparatus of capitalism against which he fought, his translation into a symbol has assured that his foothold within popular culture remains largely unassailable. While recent films and…

  17. The crystal structure of an activated Thermotoga maritima CheY with N-terminal region of FliM.

    Science.gov (United States)

    Ahn, Dae-Ro; Song, HyoJin; Kim, Jowon; Lee, Soyoung; Park, SangYoun

    2013-03-01

    In bacterial chemotaxis, the levels of phosphorylated CheY in association with FliM determine the sense of the flagella rotation, which in turn controls the bacterial swimming behavior. We report the 1.7Å resolution crystallographic structure of the Thermotoga maritima BeF(3)(-)-activated CheY in complex with the CheY-binding N-terminal region of FliM. Analysis of the structure in comparison to the previously reported Escherichia coli counterpart reveals that similar regions of H4-β5-H5 in CheY and the helix in FliM are used for the complex interfaces. Our structure also indicates that the correlated movement of Phe101 and Ser82 (F-S coupling) in T. maritima CheY upon phosphorylation and FliM binding, parallels that of Tyr106 and Thr87 (Y-T coupling) demonstrated in E. coli CheY. Furthermore, significant displacements of the β4-H4 loop in both CheYs impose a crucial role of this loop, which can be related to flagellar switch component binding or to propagating changes that is necessary during the CheY-mediated reversal of the motor. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Book Review, 50 Animali che hanno cambiato il corso della Storia, Eric Chaline

    Directory of Open Access Journals (Sweden)

    Manuel Graziani

    2013-06-01

    Full Text Available Copertina rigida "anticata", brossura cucita, carta di pregio, grafica curata nei minimi dettagli. Rientra senza dubbio nel novero della pubblicistica divulgativa di qualità questo volume uscito in Italia per i tipi di Ricca Editore. Un volume, elegante e classico, che racconta l'evoluzione dell'uomo da cacciatore ad agricoltore/pastore e, più in generale, di come ha preso piede nella storia il nuovo approccio nei confronti del regno animale. "Oltre al ruolo nel commercio e nell'agricoltura" scrive l'autore, "gli animali hanno contribuito in diversi altri modi alla cultura e alla storia dell'uomo. Alcuni come il leone, lo scarabeo sacro, il cobra e l'aquila di mare testa bianca hanno una lunga storia come simboli politici e religiosi. Nel campo della scienza e della medicina, lo studio di animali come il moscerino della frutta, il fringuello e l'iguanodonte è stato determinante per lo sviluppo della nostra conoscenza dell'evoluzione del mondo naturale."Ad ognuno dei 50 animali "che hanno cambiato il corso della Storia" viene dedicato un paragrafo sintetico, ma comunque esaustivo, corredato da foto, illustrazioni, immagini d'epoca e brevi notizie storiche, curiose e al contempo istruttive. Cosa unisce la zanzara al gin tonic? E l'ape alla mandorla? Lo sapevate che Buffalo Bill dove aver cacciato 4.000 bisonti nella sola stagione 1867-1868 divenne uno strenuo difensore della creatura vivente più grande dell'America del Nord? E che il lombrico, oltre alla sua incessante azione di riciclo biologico e minerale, è considerato una vera prelibatezza dai Maori della Nuova Zelanda? E ancora, che durante la seconda guerra mondiale un piccione chiamato G.I. Joe ricevette una medaglia dall'esercito degli Stati Uniti per aver salvato oltre mille persone? Oppure che, in contrasto con le superstizioni occidentali secondo le quali il gatto è di cattivo auspicio, in Giappone i gatti sono considerati dei veri portafortuna e che lo sport del polo ebbe origine

  19. Noi siamo quello che ricordiamo - Le frazze di Crucoli: il teatro, il rito, il riscatto sociale

    Directory of Open Access Journals (Sweden)

    Tonia Mingrone

    2012-01-01

    Full Text Available Abstract - IT Questo lavoro nasce da una ricerca di campo sulle frazze, termine dialettale che indica le farse di Carnevale che si rappresentavano fino a cinquant’anni fa in molti paesi calabresi, tra cui il mio, Crucoli, in provincia di Crotone. Lo scopo di questo lavoro non è fare un resoconto esaustivo di tutto ciò che accadeva a Crucoli durante la celebrazione del Carnevale, impresa assai difficile dal momento che non ci sono documenti scritti e quindi bisogna affidarsi ai racconti orali delle persone intervistate, spesso non fedeli alla realtà, perché modificati dal tempo e dalla memoria. L’approccio con cui ho intrapreso questa ricerca è sicuramente legato all’aspetto teatrale e performativo dell’evento, senza trascurarne la rilevanza antropologica. Il materiale raccolto è frutto di interviste e colloqui con la gente del posto unito ad un grande lavoro di ricerca bibliografica di autori che avevano trattato di questo argomento in relazione ai loro paesi di origine.Lo scopo è quello di delineare l’organizzazione e lo svolgimento delle frazze, cercando di ricostruire la sua durata e le ripercussioni sulla comunità, nonché dimostrare ancora una volta come il teatro, messo a disposizione di alcuni eventi, diventi un mezzo forte di liberazione e di contestazione. Abstract - FR Cet article prend sa naissance par une recherche sur champ concernant les frazze, terme dialectal qui dénote les farces du Carnaval mises en scène jusqu'à il y a cinquante ans dans plusieurs villages en Calabria, entre eux le mien, Crucoli, dans la province de Crotone. La raison de ce travail n'est pas d'accomplir un compte rendu exhaustif de tout ce qui avait lieu à Crucoli pendant la célébration du Carnaval, l'exploit étant très difficile, du moment qu'aucun document écrit a été parvenu et par conséquence il est nécessaire de se remettre aux contes des témoins interviewés, souvent pas fidèles au réel, parce-que détournés par les

  20. The Role of SwrA, DegU and PD3 in fla/che Expression in B. subtilis

    Science.gov (United States)

    Mordini, Serena; Osera, Cecilia; Marini, Simone; Scavone, Francesco; Bellazzi, Riccardo; Galizzi, Alessandro; Calvio, Cinzia

    2013-01-01

    In B. subtilis swarming and robust swimming motility require the positive trigger of SwrA on fla/che operon expression. Despite having an essential and specific activity, how SwrA executes this task has remained elusive thus far. We demonstrate here that SwrA acts at the main σA-dependent fla/che promoter PA(fla/che) through DegU. Electrophoretic mobility shift assays (EMSA) reveal that SwrA forms a complex with the phosphorylated form of DegU (DegU~P) at PA(fla/che) while it is unable to do so with either unphosphorylated DegU or the DegU32(Hy) mutant protein. Motility assays show that a highly phosphorylated DegU is not detrimental for flagellar motility provided that SwrA is present; however, DegU~P represses PA(fla/che) in the absence of SwrA. Overall, our data support a model in which DegU~P is a dual regulator, acting either as a repressor when alone or as a positive regulator of PA(fla/che) when combined with SwrA. Finally, we demonstrate that the σD-dependent PD3(fla/che) promoter plays an important role in motility, representing a contingent feedback loop necessary to maintain basal motility when swrA is switched to the non-functional swrA- status. PMID:24386445

  1. Site-specific and synergistic stimulation of methylation on the bacterial chemotaxis receptor Tsr by serine and CheW

    Directory of Open Access Journals (Sweden)

    Weis Robert M

    2005-03-01

    Full Text Available Abstract Background Specific glutamates in the methyl-accepting chemotaxis proteins (MCPs of Escherichia coli are modified during sensory adaptation. Attractants that bind to MCPs are known to increase the rate of receptor modification, as with serine and the serine receptor (Tsr, which contributes to an increase in the steady-state (adapted methylation level. However, MCPs form ternary complexes with two cytoplasmic signaling proteins, the kinase (CheA and an adaptor protein (CheW, but their influences on receptor methylation are unknown. Here, the influence of CheW on the rate of Tsr methylation has been studied to identify contributions to the process of adaptation. Results Methyl group incorporation was measured in a series of membrane samples in which the Tsr molecules were engineered to have one available methyl-accepting glutamate residue (297, 304, 311 or 493. The relative rates at these sites (0.14, 0.05, 0.05 and 1, respectively differed from those found previously for the aspartate receptor (Tar, which was in part due to sequence differences between Tar and Tsr near site four. The addition of CheW generated unexpectedly large and site-specific rate increases, equal to or larger than the increases produced by serine. The increases produced by serine and CheW (added separately were the largest at site one, ~3 and 6-fold, respectively, and the least at site four, no change and ~2-fold, respectively. The rate increases were even larger when serine and CheW were added together, larger than the sums of the increases produced by serine and CheW added separately (except site four. This resulted in substantially larger serine-stimulated increases when CheW was present. Also, CheW enhanced methylation rates when either two or all four sites were available. Conclusion The increase in the rate of receptor methylation upon CheW binding contributes significantly to the ligand specificity and kinetics of sensory adaptation. The synergistic effect of

  2. The Pseudomonas aeruginosa chemotaxis methyltransferase CheR1 impacts on bacterial surface sampling.

    Directory of Open Access Journals (Sweden)

    Juliane Schmidt

    Full Text Available The characterization of factors contributing to the formation and development of surface-associated bacterial communities known as biofilms has become an area of intense interest since biofilms have a major impact on human health, the environment and industry. Various studies have demonstrated that motility, including swimming, swarming and twitching, seems to play an important role in the surface colonization and establishment of structured biofilms. Thereby, the impact of chemotaxis on biofilm formation has been less intensively studied. Pseudomonas aeruginosa has a very complex chemosensory system with two Che systems implicated in flagella-mediated motility. In this study, we demonstrate that the chemotaxis protein CheR1 is a methyltransferase that binds S-adenosylmethionine and transfers a methyl group from this methyl donor to the chemoreceptor PctA, an activity which can be stimulated by the attractant serine but not by glutamine. We furthermore demonstrate that CheR1 does not only play a role in flagella-mediated chemotaxis but that its activity is essential for the formation and maintenance of bacterial biofilm structures. We propose a model in which motility and chemotaxis impact on initial attachment processes, dispersion and reattachment and increase the efficiency and frequency of surface sampling in P. aeruginosa.

  3. The 3.2 Å resolution structure of a receptor: CheA:CheW signaling complex defines overlapping binding sites and key residue interactions within bacterial chemosensory arrays.

    Science.gov (United States)

    Li, Xiaoxiao; Fleetwood, Aaron D; Bayas, Camille; Bilwes, Alexandrine M; Ortega, Davi R; Falke, Joseph J; Zhulin, Igor B; Crane, Brian R

    2013-06-04

    Bacterial chemosensory arrays are composed of extended networks of chemoreceptors (also known as methyl-accepting chemotaxis proteins, MCPs), the histidine kinase CheA, and the adaptor protein CheW. Models of these arrays have been developed from cryoelectron microscopy, crystal structures of binary and ternary complexes, NMR spectroscopy, mutational, data and biochemical studies. A new 3.2 Å resolution crystal structure of a Thermotoga maritima MCP protein interaction region in complex with the CheA kinase-regulatory module (P4-P5) and adaptor protein CheW provides sufficient detail to define residue contacts at the interfaces formed among the three proteins. As in a previous 4.5 Å resolution structure, CheA-P5 and CheW interact through conserved hydrophobic surfaces at the ends of their β-barrels to form pseudo 6-fold symmetric rings in which the two proteins alternate around the circumference. The interface between P5 subdomain 1 and CheW subdomain 2 was anticipated from previous studies, whereas the related interface between CheW subdomain 1 and P5 subdomain 2 has only been observed in these ring assemblies. The receptor forms an unexpected structure in that the helical hairpin tip of each subunit has "unzipped" into a continuous α-helix; four such helices associate into a bundle, and the tetramers bridge adjacent P5-CheW rings in the lattice through interactions with both P5 and CheW. P5 and CheW each bind a receptor helix with a groove of conserved hydrophobic residues between subdomains 1 and 2. P5 binds the receptor helix N-terminal to the tip region (lower site), whereas CheW binds the same helix with inverted polarity near the bundle end (upper site). Sequence comparisons among different evolutionary classes of chemotaxis proteins show that the binding partners undergo correlated changes at key residue positions that involve the lower site. Such evolutionary analyses argue that both CheW and P5 bind to the receptor tip at overlapping positions

  4. Che Guevara

    DEFF Research Database (Denmark)

    Cristoffanini, Pablo Rolando

    2014-01-01

    with the achievements and connotations of the Cuban Revolution in the context of the Cold War. The current meanings of the image must be read in the context of the global consumer culture. The article analyzes and explains how a conjunction of factors such as communication strategies and the connotations of his image...

  5. Buchbesprechung: Waldforschung im Nationalpark Harz – Waldforschungsfläche Bruchberg: Methodik und Aufnahme 2008/09

    OpenAIRE

    Hetsch, Wolfgang

    2013-01-01

    Besprochen wird das folgende Werk: Nationalparkverwaltung Harz (2012): Waldforschung im Nationalpark Harz – Waldforschungsfläche Bruchberg: Methodik und Aufnahme 2008/09. – Schriftenreihe aus dem Nationalpark Harz, Bd.9, 120 S.

  6. Performing Mineral Hydration Experiments in the CheMin Diffractometer on Mars

    Science.gov (United States)

    Vaniman, D. T.; Yen, A. S.; Rampe, E. B.; Blake, D. F.; Chipera, S. J.; Morookian, J. M.; Ming, D. W.; Bristow, T. F.; Morris, R. V.; Geller, R.; hide

    2016-01-01

    Laboratory work is the cornerstone of experimental planetary geochemistry, mineralogy, and petrology, but much is to be gained by "experiments" while on a planet surface. Earth-bound experiments are often limited in ability to control multiple conditions relevant to planetary bodies (e.g. cycles in temperature and vapor pressure of water), but observations on-planet provide a unique opportunity where conditions are native to the planet and those affected by sampling and analysis can be constrained. The CheMin XRD instrument on Mars Science Laboratory has been able to test mineral hydration in samples held for up to 300 Mars days (sols). Clay minerals sampled at Yellowknife Bay early in the mission had both collapsed (10 Å) and expanded (13.2 Å) basal spacing. Collapsed interlayers were expected, but larger spacing was not; it was uncertain whether larger basal spacing would collapse on prolonged exposure to warmer conditions inside CheMin. Observation over several hundred sols showed no collapse, with the conclusion that expanded interlayer spacing was due to partial intercalation by metal-hydroxyl groups that resist dehydration. More recently, a sample of the Murray Formation, Oudam, provided the first XRD detection of gypsum and a chance to observe gypsum stability. Laboratory work suggests gypsum should be stable at Mars surface conditions, and indeed gypsum has been observed from orbit at higher latitudes and in thick veins at Yellowknife Bay by Mastcam reflectance spectra. Laboratory experiments have shown that on dehydration the gypsum would not become X-ray amorphous but would rather transform to a water-deficient bassanite structure. Over a period of 37 sols, it was observed that the Oudam sample in CheMin transformed from an assemblage of gypsum+anhydrite, to gypsum+bassanite+anhydrite, and finally to bassanite+anhydrite. Mg-sulfates were also anticipated but have not been observed in CheMin despite chemical evidence for their presence. Unlike gypsum

  7. L’immaginazione al lavoro. Che cosa e come conosciamo dal romanzo

    Directory of Open Access Journals (Sweden)

    Gianluca Consoli

    2011-12-01

    Full Text Available L’articolo delinea i fondamenti di un’epistemologia del romanzo, rispondendo alle domande di base: che cosa e come possiamo conoscere attraverso il romanzo. A partire dalla definizione del romanzo come racconto di finzione, viene sviluppata  una posizione di cognitivismo radicale, per la quale il romanzo (a produce conoscenza modale; (b giustifica questa conoscenza in base al principio della verosimiglianza; (c favorisce l’apprendimento per esperienza in virtù dell’esemplificazione immaginativa. Le tesi proposte vengono corroborate in riferimento ai recenti dati sperimentali ottenuti dalle scienze cognitive, in particolare dalla psicologia cognitiva, sull’immaginazione, la finzione, la simulazione.

  8. Stealing or Steeling the Image? The Failed Branding of the Guerrillero Heroico image of Che Guevara

    OpenAIRE

    Maria-Carolina Cambre

    2012-01-01

    This article traces the ongoing tension between those who would characterize Alberto Korda’s famous image of Che Guevara, The Guerrillero Heroico, as a brand, trademark or logo, and those who insist it is a political/cultural icon and non-commercial and that these categories are mutually exclusive. The question of whether the image has been emptied of political content, and the debate around the copyrighting of an image considered by many to be in the public domain and a cultural icon are exp...

  9. Indirect cannibalism by crèche-aged American White Pelican (Pelecanus erythrorhynchos) chicks

    Science.gov (United States)

    Bartos, Alisa J.; Sovada, Marsha A.; Igl, Lawrence D.; Pietz, Pamela J.

    2013-01-01

    At nesting colonies of American White Pelicans (Pelecanus erythrorhynchos), many chicks die from siblicide, severe weather, and disease; this results in carcasses available for scavenging by conspecifics (i.e., indirect cannibalism). Indirect cannibalism has not been reported previously for this species. We describe five cases of crèche-aged American White Pelican chicks consuming or attempting to consume dead younger chicks at two nesting colonies in the northern plains of North America. Cannibalism in the American White Pelican appears to be rare and likely plays no role in the species’ population ecology or dynamics; however, it might be an important survival strategy of individual chicks when food resources are limited.

  10. Tassi di cambio fluttuanti, deprezzamento valutario e domanda effettiva

    Directory of Open Access Journals (Sweden)

    Julio López

    2006-09-01

    Full Text Available Il presente articolo esamina i vantaggi relativi dei tassi di cambio fluttuanti nei confronti di un regime di tassi di cambio a parità rigidamente ancorate (hard peg, ponendo particolare enfasi sulle implicazioni per la domanda effettiva. In particolare, esso valuta se un deprezzamento della valuta abbia un effetto benefico sulla domanda aggregata e dunque sull’occupazione. Si sostiene che tale questione è centrale per il principio della domanda effettiva, e che l’idea che un deprezzamento valutario sia in grado di stabilizzare la domanda effettiva equivale in larga misura a sostenere che la flessibilità (verso il basso dei salari nominali (e reali possa assicurare la piena occupazione. Coerentemente con ciò, viene analizzata la relazione tra la flessibilità verso il basso dei salari e la domanda effettiva, e viene valutata criticamente (dal punto di vista sia teorico sia empirico l’ipotesi che la flessibilità del tasso di cambio possa avere proprietà stabilizzanti quando si tenga conto di shock esogeni di varia natura. L’articolo si chiude con brevi deduzioni di teoria e di politica economiche.

  11. Finally a crèche at CERN, thanks to the Staff Association

    CERN Multimedia

    Staff Association

    2013-01-01

    Setting up at CERN a collective structure to mind children younger than two years, a so-called “crèche”, has been discussed at least since the early 1990s. Then, in February 2001, the Equal Opportunities Advisory Panel produced a memo to the Director of Administration in which it “invites the CERN Management to re-consider the possibility of creating a crèche at CERN”. As a result an ad hoc task force (“Bethléem”) was set up, which based its work on an informal questionnaire sent to CERN families with small children. Its study came up with some relevant parameters for “should CERN Management intend to undertake a minimal effort toward solving the crèche problem for its staff members”. Nothing was undertaken at that time. In the framework of the 2005 five yearly review “Working Group 6: Crèche” made another study of public and private  cr&a...

  12. CheS-Mapper - Chemical Space Mapping and Visualization in 3D

    Directory of Open Access Journals (Sweden)

    Gütlein Martin

    2012-03-01

    Full Text Available Abstract Analyzing chemical datasets is a challenging task for scientific researchers in the field of chemoinformatics. It is important, yet difficult to understand the relationship between the structure of chemical compounds, their physico-chemical properties, and biological or toxic effects. To that respect, visualization tools can help to better comprehend the underlying correlations. Our recently developed 3D molecular viewer CheS-Mapper (Chemical Space Mapper divides large datasets into clusters of similar compounds and consequently arranges them in 3D space, such that their spatial proximity reflects their similarity. The user can indirectly determine similarity, by selecting which features to employ in the process. The tool can use and calculate different kind of features, like structural fragments as well as quantitative chemical descriptors. These features can be highlighted within CheS-Mapper, which aids the chemist to better understand patterns and regularities and relate the observations to established scientific knowledge. As a final function, the tool can also be used to select and export specific subsets of a given dataset for further analysis.

  13. Stealing or Steeling the Image? The Failed Branding of the Guerrillero Heroico image of Che Guevara

    Directory of Open Access Journals (Sweden)

    Maria-Carolina Cambre

    2012-05-01

    Full Text Available This article traces the ongoing tension between those who would characterize Alberto Korda’s famous image of Che Guevara, The Guerrillero Heroico, as a brand, trademark or logo, and those who insist it is a political/cultural icon and non-commercial and that these categories are mutually exclusive. The question of whether the image has been emptied of political content, and the debate around the copyrighting of an image considered by many to be in the public domain and a cultural icon are explored. The long-lasting struggle over the meanings and collective memories associated with this image indicate the possibility that both processes of commodification and radicalization of the image of Che Guevara can coexist. Using the literature on consumer research to engage definitions of branding as a commercially geared venture, this article teases out the problematics of different uses of the photograph and its derivatives, and highlights ambiguities around the notions of creation and authorship. After examining this image’s role within Cuba, Cuban use outside of Cuba, and its commercial and non-commercial uses by non-Cubans, I conclude that attempts at branding products with this particular image fail, and therefore its copyrighting is irrelevant.

  14. Crew Health Care System (CHeCS) Design Research, Documentations, and Evaluations

    Science.gov (United States)

    CLement, Bethany M.

    2011-01-01

    The Crew Health Care System (CHeCS) is a group within the Space Life Science Directorate (SLSD) that focuses on the overall health of astronauts by reinforcing the three divisions - the Environmental Maintenance System (EMS), the Countermeasures System (CMS), and the Health Maintenance System (HMS). This internship provided opportunity to gain knowledge, experience, and skills in CHeCS engineering and operations tasks. Various and differing tasks allowed for occasions to work independently, network to get things done, and show leadership abilities. Specific exercises included reviewing hardware certification, operations, and documentation within the ongoing Med Kit Redesign (MKR) project, and learning, writing, and working various common pieces of paperwork used in the engineering and design process. Another project focused on the distribution of various pieces of hardware to off-site research facilities with an interest in space flight health care. The main focus of this internship, though, was on a broad and encompassing understanding of the engineering process as time was spent looking at each individual step in a variety of settings and tasks.

  15. The new "Jardin de Capucine" crèche brings a breath of fresh air for young CERN parents

    CERN Multimedia

    HR Department

    2011-01-01

    On 19 January 2011, CERN's Director-General, Rolf Heuer, signed an agreement with the company "Le Jardin de Zébulon" for the provision of 40 places at the "Jardin de Capucine", a new private crèche due to open this autumn.   In 2008, the "Jardin de Zébulon", a private bilingual crèche for children aged 1 to 4, was opened by Ariane Boucheron at the Technoparc industrial estate in Saint-Genis Pouilly (France). The following year, the number of places was increased from 20 to 37 to meet demand. The "Jardin de Zébulon" has taken in a number of children of CERN personnel ever since it was created. With no let-up in the demand for new crèche places, Ariane Boucher is currently engaged in the construction of a new centre, the "Jardin de Capucine", next-door to the existing crèche. Forty places at the new crèche will...

  16. Structure of the Constitutively Active Double Mutant CheY[superscript D13K Y106W] Alone and in Complex with a FliM Peptide

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, Collin M.; Quillin, Michael L.; Campos, Andres; Lu, Justine; McEvoy, Megan M.; Hausrath, Andrew C.; Westbrook, Edwin M.; Matsumura, Philip; Matthews, Brian W.; Dahlquist, Frederick W. (MBC); (Oregon)

    2010-11-16

    CheY is a member of the response regulator protein superfamily that controls the chemotactic swimming response of motile bacteria. The CheY double mutant D13K Y106W (CheY**) is resistant to phosphorylation, yet is a highly effective mimic of phosphorylated CheY in vivo and in vitro. The conformational attributes of this protein that enable it to signal in a phosphorylation-independent manner are unknown. We have solved the crystal structure of selenomethionine-substituted CheY** in the presence of its target, a peptide (FliM{sub 16}) derived from the flagellar motor switch, FliM, to 1.5 {angstrom} resolution with an R-factor of 19.6%. The asymmetric unit contains four CheY** molecules, two with FliM{sub 16} bound, and two without. The two CheY** molecules in the asymmetric unit that are bound to FliM{sub 16} adopt a conformation similar to BeF{sub 3}{sup -}-activated wild-type CheY, and also bind FliM{sub 16} in a nearly identical manner. The CheY** molecules that do not bind FliM{sub 16} are found in a conformation similar to unphosphorylated wild-type CheY, suggesting that the active phenotype of this mutant is enabled by a facile interconversion between the active and inactive conformations. Finally, we propose a ligand-binding model for CheY and CheY**, in which Ile95 changes conformation in a Tyr/Trp106-dependent manner to accommodate FliM.

  17. Astrobiological Significance of Definitive Mineralogical Analysis of Martian Surface Samples Using the CheMin XRD/XRF Instrument

    Science.gov (United States)

    Feldman, S. M.; Blake, D. F.; Sarrazin, P.; Bish, D. L.; Chipera, S. J.; Vaniman, D. T.; Collins, S.

    2004-01-01

    The search for evidence of habitability, or of extant or extinct life on Mars, will initially be a search for evidence of past or present conditions supportive of life. The three key requirements for the emergence of life are thought to be liquid water; a suitable energy source; and chemical building blocks. CheMin is a miniaturized XRD/XRF (X-Ray diffraction / X-ray fluorescence) instrument which has been developed for definitive mineralogic analysis of soils and rocks on the Martian surface. The CheMin instrument can provide information that is highly relevant to each of these habitability requirements as summarized below.

  18. Sequence of the flaA (cheC) locus of Escherichia coli and discovery of a new gene.

    OpenAIRE

    Kuo, S C; Koshland, D E

    1986-01-01

    The flaA (cheC) locus from Escherichia coli is important in controlling the rotational direction of flagella during chemotaxis. The locus was sequenced, and a site of transcriptional initiation was determined. Two reading frames, flaAI and flaAII, span the locus. flaAII corresponds to certain flaA and cheC mutations, and has some unusual features in the predicted secondary structure. flaAI, however, has not been identified previously, but a flaAI deletion, which produced a truncated FlaAI pep...

  19. Indagine sull’utilizzo delle tecniche di visualizzazione 2D e 3D che rappresentano il cambiamento del paesaggio urbano storico

    Directory of Open Access Journals (Sweden)

    Turgay Kerem Koramaz

    2011-06-01

    Full Text Available Al fine di descrivere il cambiamento del paesaggio urbano di siti riferiti alla città, gli strumenti moderni di visualizzazione possono essere utilizzati per aumentare le possibilità di rappresentazione, in misura maggiore rispetto ai metodi tradizionali. Studi recenti di conservazione ed interventi effettuati hanno indicato un cambiamento significativo nel paesaggio urbano storico di Zeyrek: questo articolo presenta le possibilità di rappresentazione insite nella tecnica di mappatura bidimensionale e nella realizzazione di un modello tridimensionale del comparto, utilizzati nella definizione del cambiamento del paesaggio urbano. Per valutare l’effettiva capacità di rappresentazione per mezzo di risposte da parte degli utenti dei modelli, è stato sottoposto un questionario agli studenti di laurea specialistica della Facoltà di Architettura, ai professionisti in enti di pianificazione e di conservazione ed agli studenti delle scuole superiori. A conclusione principale dello studio, si è compreso come il cambiamento del paesaggio urbano sia definito meglio nel modello urbano tridimensionale che nella tecnica di mappatura bidimensionale, in termini di rappresentazione dei dettagli architettonici e delle caratteristiche strutturali del luogo.

  20. CHeCS (Crew Health Care Systems): International Space Station (ISS) Medical Hardware Catalog. Version 10.0

    Science.gov (United States)

    2011-01-01

    The purpose of this catalog is to provide a detailed description of each piece of hardware in the Crew Health Care System (CHeCS), including subpacks associated with the hardware, and to briefly describe the interfaces between the hardware and the ISS. The primary user of this document is the Space Medicine/Medical Operations ISS Biomedical Flight Controllers (ISS BMEs).

  1. Relative Roles of the fla/che PA, PD-3, and PsigD Promoters in Regulating Motility and sigD Expression in Bacillus subtilis

    Science.gov (United States)

    West, Joyce T.; Estacio, William; Márquez-Magaña, Leticia

    2000-01-01

    Three promoters have been identified as having potentially important regulatory roles in governing expression of the fla/che operon and of sigD, a gene that lies near the 3′ end of the operon. Two of these promoters, fla/che PA and PD-3, lie upstream of the >26-kb fla/che operon. The third promoter, PsigD, lies within the operon, immediately upstream of sigD. fla/che PA, transcribed by EςA, lies ≥24 kb upstream of sigD and appears to be largely responsible for sigD expression. PD-3, transcribed by EςD, has been proposed to participate in an autoregulatory positive feedback loop. PsigD, a minor ςA-dependent promoter, has been implicated as essential for normal expression of the fla/che operon. We tested the proposed functions of these promoters in experiments that utilized strains that bear chromosomal deletions of fla/che PA, PD-3, or PsigD. Our analysis of these strains indicates that fla/che PA is absolutely essential for motility, that PD-3 does not function in positive feedback regulation of sigD expression, and that PsigD is not essential for normal fla/che expression. Further, our results suggest that an additional promoter(s) contributes to sigD expression. PMID:10940026

  2. Molecular interaction and cellular location of RecA and CheW proteins in Salmonella enterica during SOS response and their implication in swarming

    Directory of Open Access Journals (Sweden)

    Oihane Irazoki

    2016-10-01

    Full Text Available In addition to its role in DNA damage repair and recombination, the RecA protein, through its interaction with CheW, is involved in swarming motility, a form of flagella-dependent movement across surfaces. In order to better understand how SOS response modulates swarming, in this work the location of RecA and CheW proteins within the swarming cells has been studied by using super-resolution microscopy. Further, and after in silico docking studies, the specific RecA and CheW regions associated with the RecA-CheW interaction have also been confirmed by site-directed mutagenesis and immunoprecipitation techniques. Our results point out that the CheW distribution changes, from the cell poles to foci distributed in a helical pattern along the cell axis when SOS response is activated or RecA protein is overexpressed. In this situation, the CheW presents the same subcellular location as that of RecA, pointing out that the previously described RecA storage structures may be modulators of swarming motility. Data reported herein not only confirmed that the RecA-CheW pair is essential for swarming motility but it is directly involved in the CheW distribution change associated to SOS response activation. A model explaining not only the mechanism by which DNA damage modulates swarming but also how both the lack and the excess of RecA protein impair this motility is proposed.

  3. European analytical column No. 36 from the Division of Analytical Chemistry (DAC) of the European Association for Chemical and Molecular Sciences (EuCheMS)

    DEFF Research Database (Denmark)

    Karlberg, Bo; Emons, Hendrik; Andersen, Jens Enevold Thaulov

    2008-01-01

    European analytical column no. 36 from the division of analytical chemistry (DAC) of the European association for chemical and molecular sciences (EuCheMS)......European analytical column no. 36 from the division of analytical chemistry (DAC) of the European association for chemical and molecular sciences (EuCheMS)...

  4. El Che - más que médico

    Directory of Open Access Journals (Sweden)

    Natalia I. Osorio Curbelo

    2015-12-01

    Full Text Available Revolucionario, dirigente político, comandante guerrillero, intelectual y médico.  Uno de los íconos del siglo XX.  Nació en Rosario, Argentina, el 14 de junio de 1928. En 1938, con apenas 10 años, el padre le enseñó a jugar Ajedrez en el transcurso del año, deporte que no dejaría de practicar nunca más y lo estudiaría por siempre. En 1939 supo de la existencia de Cuba, pues teniendo 11 años, cuando vivía en Alta Gracia, en Buenos Aires se desarrollaba la VII Olimpiada de Ajedrez y el más conocido de los ajedrecistas cubanos José Raúl Capablanca, obtuvo la medalla de Oro en el primer tablero, convirtiéndose en noticia mundial. La gran pasión por el juego ciencia  se puso de manifiesto durante toda su vida, jugó Ajedrez cuando estaba viajando en un avión, cuando  estuvo detenido en alguna estación policial o, simplemente, a las tres de la madrugada recibía una delegación mexicana para jugar una partida después de conversar sobre los temas generales comunes. Ernesto Guevara, eternamente Che, revolucionario integral y multifacético, sintió gran afición por los deportes y aunque por lo general se le cita como amante del ajedrez y el fútbol, también, desde niño, practicó con derroche de coraje y voluntad otros no tan divulgados. A sus prácticas deportivas también se entregó con la voluntad, coraje y pasión que lo caracterizaron a lo largo de su vida. Luego del triunfo de la Revolución cubana, en la que ganó  los grados de Comandante, hubo  un deporte priorizado  en la vida del Che: el Ajedrez.  Dos veces ganó en los campeonatos patrocinados por el Ministerio de Industria, que él presidía,  y participó, además, en los Torneos del INDER donde ascendió, por los resultados alcanzados, a la primera categoría. Se enfrentó en partidas simultáneas a varios de los mejores jugadores de esos días, entre ellos los grandes maestros soviéticos Victor Korchnoi y Mijail Tal y el argentino Miguel Najdorf, d

  5. RELÉ ELECTRÓNICO PARA LA DETECCIÓN DEL MOVIMIENTO EN LOS TANQUES DE SEDIMENTACIÓN DE LA EMPRESA COMANDANTE ¨ERNESTO CHE GUEVARA¨

    Directory of Open Access Journals (Sweden)

    Orlys Ernesto Torres Breffe

    2011-02-01

    Full Text Available En este trabajo se muestran los resultados del diseño de un dispositivo electrónico para detectar el movimiento del tanquede sedimentación de la planta de lixiviación de la Empresa Ernesto Che Guevara.Estos tanque actualmente se encuentran sin esta protección y su parada por avería solo es detectada de forma visual por eloperario o cuando la densidad de la pulpa aumente a valores tan altos que sea reflejado en el sistema de monitoreo instalado(EROS. La parada inadvertida de estos tanque casi siempre sucede por razones fácilmente corregibles, pero si no se detectaa tiempo la sedimentación del minerales es casi inevitable y las pérdidas de recursos y materiales son cuantiosas.La propuesta electrónica en sustitución a las desechas electromagnéticas, es muy barata y su reproducción es fácilmenterealizable en la propia empresa, dado que los elementos que se utiliza son clásicos, sin exigencias de fabricación, tolerancias,etc.  The main goal of this research paper is to show the electronic device design results while dealing with the location of thesedimentation tank on the leaching plant located on Ernesto Che Guevara factory.Nowadays there is no protection for this tank, thus, if it stops working it can only be noticed by the engine sunner on avisual way or when the extremely high figures of the pulp density are reflected on the available monitor system (EROS.The unnoticed misfunctioning of this device is caused mainly to easily solved reasons. Nevertheless, when not detected ontime, the mineral sedimentation is almost unavoidable which results on the losses of resources.The electronic proposal to substitute the electromagnetic scraps is very cheap and easily to reproduce on the factory itself forthe needed elements are classic with no resistance and manufacture demands.

  6. Start of enrolment for the Champs-Fréchets crèche (EVE)

    CERN Document Server

    HR Department

    2008-01-01

    As announced in Bulletin 43/2007, CERN signed an agreement with the commune of Meyrin on 17 October 2007 under which 20 places will be reserved for the children of CERN personnel in the Champs-Fréchets day care centre (EVE), which will open on Monday, 25 August, and CERN will contribute to the funding. This agreement allows members of the CERN personnel (employees and associates) access to the crèche, for children aged between 4 months and 4 years, irrespective of where they are living. Applications for the school year starting autumn 2008 will be accepted from Monday 17 March until Monday 30 June 2008. Members of the personnel must complete the enrolment formalities with the Meyrin infant education service themselves: Mairie de Meyrin Service de la Petite Enfance 2 rue des Boudines Case postale 367 - 1217 Meyrin 1 - Tel. + 41 (0)22 782 21 21 mailto:meyrin@meyrin.ch http://www.meyrin.ch/petiteenfance Application forms (in PDF) can be downloaded from the website of the com...

  7. Neanderthal hand and foot remains from Moula-Guercy, Ardèche, France.

    Science.gov (United States)

    Mersey, Ben; Jabbour, Rebecca S; Brudvik, Kyle; Defleur, Alban

    2013-12-01

    The hand and foot remains from Moula-Guercy cave (Ardèche, France) comprise 24 specimens of Eemian age (ca. 120 ka). The specimens include primarily complete elements, which are rare among the Moula-Guercy postcrania. The hand remains have several characteristic Neanderthal traits including a laterally facing (parasagittally oriented) second metacarpal-capitate articulation, a short styloid process, a wide proximal articular surface on the third metacarpal, and absolutely expanded apical tuberosities on the distal hand phalanges relative to modern humans. The foot remains include several incomplete elements along with an antimeric pair of naviculars, a medial cuneiform and cuboid, and a single complete element from each of the distal segments (one each: metatarsal, proximal foot phalanx, intermediate foot phalanx, distal foot phalanx). Consistent among the specimens are relatively wide diaphyses for length in the metatarsals and phalanges and large and prominent muscle attachments, both consistent with previously published Neanderthal morphology. The hand and foot collection from Moula-Guercy is an important dataset for future studies of Neanderthal functional morphology, dexterity, and behavior as it represents a previously undersampled time period for European Neanderthals. Copyright © 2013 Wiley Periodicals, Inc.

  8. Neanderthal axial and appendicular remains from Moula-Guercy, Ardèche, France.

    Science.gov (United States)

    Mersey, Ben; Brudvik, Kyle; Black, Michael T; Defleur, Alban

    2013-12-01

    Excavations carried out during the 1990s at Moula-Guercy cave Ardèche, France, yielded 108 hominid specimens dating to 100-120 Ka. In this paper, we describe and compare the 39 axial and appendicular specimens not including hand and foot bones. Among these remains are a large adult femur, several clavicles, a likely antimeric pair of radial heads, and a nearly complete superior pubic ramus. Analyses of this material indicate a clear affinity with Neanderthals by the presence of large and robust muscle attachments, thick long bone cortices, a long pubic ramus, and a superoinferiorly flattened clavicle shaft. The recovered remains reveal the presence of a mature male, a smaller mature individual, possibly a reproductive age female, an immature individual of age 10-12, and a second immature individual of age 4. Future analyses on the Moula-Guercy remains will illuminate ties to other known Neanderthal populations and contribute to the ongoing debate over the relative rate of Neanderthal metric growth. Copyright © 2013 Wiley Periodicals, Inc.

  9. Role for cheR of Vibrio fischeri in the Vibrio-squid symbiosis.

    Science.gov (United States)

    Deloney-Marino, Cindy R; Visick, Karen L

    2012-01-01

    Upon hatching, the Hawaiian squid Euprymna scolopes is rapidly colonized by its symbiotic partner, the bioluminescent marine bacterium Vibrio fischeri . Vibrio fischeri cells present in the seawater enter the light organ of juvenile squid in a process that requires bacterial motility. In this study, we investigated the role chemotaxis may play in establishing this symbiotic colonization. Previously, we reported that V. fischeri migrates toward numerous attractants, including N-acetylneuraminic acid (NANA), a component of squid mucus. However, whether or not migration toward an attractant such as squid-derived NANA helps the bacterium to localize toward the light organ is unknown. When tested for the ability to colonize juvenile squid, a V. fischeri chemotaxis mutant defective for the methyltransferase CheR was outcompeted by the wild-type strain in co-inoculation experiments, even when the mutant was present in fourfold excess. Our results suggest that the ability to perform chemotaxis is an advantage during colonization, but not essential.

  10. Nutritional status of orang asli (che wong tribe) adults in krau wildlife reserve, pahang.

    Science.gov (United States)

    Haemamalar, K; Zalilah, M S; Neng Azhanie, A

    2010-04-01

    This is a descriptive study on nutritional status of Orang Asli (Che Wong tribe) adults in Krau Wildlife Reserve. Twenty-six households, comprising 29 men and 28 women,participated in the study. Dietary diversity was assessed using food frequency questionnaire with 37 food groups. Weight, height and waist circumference were measured using standard instruments. The mean age for men and women was 39.9 ± 17.1 years and 33.7 ± 16.1 years, respectively. Most (89.5%) of the adults had no formal education and about 89.5% of households were categorised as poor. There were 13.8% underweight, 72.4% normal, 10.3% overweight and 3.3% obese men. For women, 25.0%, 46.4%, and 28.6% were underweight, normal and overweight, respectively. While none of the men had at-risk waist circumference (men >90 cm), about 21.4% of women had waist circumference of >80 cm. The mean dietary diversity score was 9.47 ± 4.15 with men (9.48 ± 3.70) and women (9.46 ± 4.63) having similar scores. There was a significant correlation between waist circumference and household income (r=0.36, pOrang Asli community undergoing nutrition transition especially among the females.

  11. The role of SwrA, DegU and P(D3) in fla/che expression in B. subtilis.

    Science.gov (United States)

    Mordini, Serena; Osera, Cecilia; Marini, Simone; Scavone, Francesco; Bellazzi, Riccardo; Galizzi, Alessandro; Calvio, Cinzia

    2013-01-01

    In B. subtilis swarming and robust swimming motility require the positive trigger of SwrA on fla/che operon expression. Despite having an essential and specific activity, how SwrA executes this task has remained elusive thus far. We demonstrate here that SwrA acts at the main σ(A)-dependent fla/che promoter PA(fla/che) through DegU. Electrophoretic mobility shift assays (EMSA) reveal that SwrA forms a complex with the phosphorylated form of DegU (DegU~P) at PA(fla/che) while it is unable to do so with either unphosphorylated DegU or the DegU32(Hy) mutant protein. Motility assays show that a highly phosphorylated DegU is not detrimental for flagellar motility provided that SwrA is present; however, DegU~P represses PA(fla/che) in the absence of SwrA. Overall, our data support a model in which DegU~P is a dual regulator, acting either as a repressor when alone or as a positive regulator of PA(fla/che) when combined with SwrA. Finally, we demonstrate that the σ(D)-dependent PD3(fla/che) promoter plays an important role in motility, representing a contingent feedback loop necessary to maintain basal motility when swrA is switched to the non-functional swrA(-) status.

  12. LE SOLUTRÉEN ANCIEN EN ARDÈCHE (FRANCE: UNE RÉVISION CRITIQUE DES INDUSTRIES LITHIQUES

    Directory of Open Access Journals (Sweden)

    Sophie Guegan

    2013-11-01

    Full Text Available S’inscrivant dans un travail de Doctorat sur les peuplements des deux rives de la vallée du Rhône au Maximum Glaciaire, cet article propose un état des connaissances sur la phase ancienne du Solutréen en Ardèche (rive droite du Rhône, donnant lieu à une révision critique des industries lithiques s’y rapportant. En effet, depuis les travaux de P.E.L. Smith et J. Combier, et plus récemment le travail d’A. Barbiero consacré aux pointes à face plance et pointes à cran d’une collection ancienne à la Baume d’Oullins (Gard-Ardèche, France, aucun réexamen global n’avait été entrepris. Trois gisements de référence pour cette phase ancienne, ont ainsi été sélectionnés: les grottes d’Oullins (Gard-Ardèche, France, de Chabot (Gard, France et de Granouly (Ardèche, France. Nous présentons ici les réslutats préliminaires à cette étude. En premier lieu, une approche typologique a été menée principalement autour de la pointe à face plane, objet emblématique de cette phase, permettant d’en préciser les principaux caractères. Dans un deuxième temps, une approche technologique a permis de confirmer l’homogénéité dans les choix techniques des Solutréens entre l’Ardèche et les régions du Sud-Ouest et du Bassin Parisien. Enfin, une étude des matières premières, a révélé pour l’heure des choix économiques étonnants pour le contexte paléo-climatique, avec des déplacements vers le nords et un franchissement du Rhône.In the frame of a doctoral dissertation on the Late Glacial Maximum occupations of both sides of the Rhône valley, this paper presents a state of the art and a critical reappraisal of the lithic assemblages from the early phases of the Solutrean in Ardeche (right bank of the Rhône river. Indeed, since the works of P.E.L. Smith and J. Combier, except the work of A. Barbiero, on the unifacial leaf-points and shouldered points from Baume d'Oullins, no complete study of these

  13. Binding of the Escherichia coli response regulator CheY to its target measured in vivo by fluorescence resonance energy transfer

    OpenAIRE

    Sourjik, Victor; Berg, Howard C.

    2002-01-01

    In Escherichia coli chemotaxis, signaling depends on modulation of the level of phosphorylation of CheY, a small protein that couples receptors and flagellar motors. Working in vivo, we used fluorescence resonance energy transfer (FRET) to measure the interaction of CheY∼P with its target, FliM. Binding of CheY∼P to FliM was found to be much less cooperative than motor switching; however, under the conditions of our experiment, most of the FliM appeared to be in the cytoplasm. We studied sign...

  14. Caractérisation de la Biomasse sèche des mosaïques forêt-savane ...

    African Journals Online (AJOL)

    SARAH

    2 sept. 2013 ... Mots clés: Carbone, Biomasse sèche, Gabon, savanes, forêt, changement climatique. ABSTRACT. Objective: Quantify the dry ... Ce réchauffement semble être lié en grande partie à la production des gaz à effet de ... La région minière de Moanda, comme les plateaux Batéké, est caractérisé par un climat.

  15. The Huguenot identity in 19th century music: The "Sechs Sprüche zum Kirchenjahr" by Felix Mendelssohn

    OpenAIRE

    Robert Weeda

    2012-01-01

    Hierdie artikel gaan oor die komponiste Felix Mendelssohn en Giacomo Meyerbeer. Meyerbeer die komponis van die opera Les Huguenots, en Mendelssohn, 'n Jood wat 'n "Calvinis" geword het. Meyerbeer vertel in die opera (1836), geanker aan die Lutherse melodie "'n Vaste Burg is onse God" die verhaal van die Bartolomeusnagmoorde. Mendelssohn, 'n bekeerling tot die sg Hugenote-religie, verwoord sy opregte geloof gedurende die jare 1843-1846 in die voortreflike musikaleuitdrukkings Sechs Sprüche zum...

  16. Apprendimento in digitale e processi cognitivi: problemi aperti e riflessioni da ri-avviare

    Directory of Open Access Journals (Sweden)

    Antonio Marzano

    2015-09-01

    Full Text Available Il contributo intende esaminare gli apporti di ricerche empiriche, nazionali e internazionali, realizzate nell’ambito della Media Education, con particolare riferimento al rapporto tra tecnologie, supporti digitali e processo di apprendimento. Nella prima parte del contributo è delineata la cornice teorica di riferimento per ricostruire il passaggio da una società monosensoriale ad una multisensoriale sempre più dominata dagli artefatti digitali. La seconda parte si concentra sui supporti digitali di lettura, in particolare sull’e-book. Dopo aver analizzato le tecnologie usate per la fruizione dei testi digitali e descritto i vantaggi e gli svantaggi del supporto digitale, ci si chiede se e quanto sia promettente l’utilizzo dell’e-book nei contesti di formazione. Ci sono numerosi problemi aperti e potenziali direttrici di indagine: le evidenze empirico-sperimentali, che su questo punto sono contrastanti, meritano ulteriori e futuri approfondimenti anche di natura epistemologica.

  17. INVESTIGACIÓN DIALÓGICA-KISHU KIMKELAY TA CHE EN EDUCACIÓN

    Directory of Open Access Journals (Sweden)

    Donatila Ferrada

    2014-01-01

    Full Text Available La investigación Dialógica-Kishu Kimkelay Ta Che -es producto de un trabajo de largo aliento desarrollado en comunidades educativas en la zona centro-sur de Chile-, focalizada en construir conocimiento científico incorporando la diversidad de culturas, territorios y lenguas presentes, específicamente en sectores sociales escasamente visibilizados por la comunidad científica. El eje central de esta investigación es la construcción colectiva del conocimiento, al interior de una comunidad de investigación, en la cual participan una diversidad de agentes, indistintamente de su posición social o escolarización, desde una comprensión de nivelación epistémica/metodológica en que cada uno es experto en el saber que porta, el cual se pone a disposición de los participantes, a fin de ir acordando los nuevos significados que pueden conducir a conseguir una mejor comprensión de los fenómenos abordados, y a generar procesos de transformación de las prácticas de quienes forman parte de la construcción colectiva. De la misma forma se reportan insumos de orden metodológico ya desarrollados en numerosos trabajos previos. Este tipo de investigación pretende ofrecer una posibilidad concreta desde la cual se reoriente la investigación educativa que se construye desde el “sur” a fin de ofrecer un conocimiento que se acerque alo que como colectivo con identidad propia, somos.

  18. Russian Orthodoxy influence on the policy of Chełm Land russification in the 19th and early 20th centuries

    Directory of Open Access Journals (Sweden)

    Melkov Andrey Sergeevich

    2016-04-01

    Full Text Available The problem of Russian Church influence on the Imperial policy of Chełm Land russification is researched in this article. Chełm, the historical region of Polish-Ukrainian borderland, used to be a part of Russia in the 19th and early 20th centuries. The russification of Chełm Land was accompanied by total abolition of the Uniate Church and forcible believers transfer into Orthodoxy. At the beginning of the 20th century there was created a draft law about Chełm Land separation from the Kingdom of Poland. Bishop of Russian Orthodox Church Eulogius (Georgievsky was responsible for solving that problem. In fact, the Imperial power used Orthodoxy for reaching the stated goals, which were the eradication of the national language and culture in Poland as well as resolving of the so-called “Ukrainian question”.

  19. Quality of the Fosso della Casaccia: analysis of the macroinvertebrates colonizing artificial substrates; Stato di qualita` del fosso della Casaccia: analisi dei macroinvertebrati che colonizzano substrati artificiali

    Energy Technology Data Exchange (ETDEWEB)

    Prato, S.; Morgana, J.G.; Antonelli, D.; Folletto, A. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Ambiente

    1999-01-01

    Aim of this work is to analyse the environmental quality of a small stream, the Fosso della Casaccia, flowing near Research Centre of ENEA (Rome, Central Italy). The study was carried out comparing zoo benthic communities of two sampling sites, chosen upstream and downstream the sewage of the Research Centre. Macro invertebrates were sampled using artificial substrates and standard hand net. Taxa number and distribution along along the watercourse were compared. Moreover, biotic index values (I.B.E.=Indice Biotico Esteso) were calculated using data on macro invertebrates collected with both sampling methodologies. Artificial substrates were also useful in establishing colonization patterns at each sampling site, and bio masses of individuals belonging to different trophic groups. The results show the greater sampling effectiveness of artificial substrates, confirming their usefulness for establishing the environmental quality. [Italiano] Il presente lavoro prende in considerazione la qualita` ambientale del Fosso della Casaccia, un piccolo corso d`acqua che scorre in prossimita` del Centro di Ricerche ENEA Casaccia (Italia Centrale). Lo studio e` stato realizzato in base al confronto fra le comunita` zoobentoniche di due stazioni sperimentali situate a monte e a valle dello scarico di acque reflue del centro. Il campionamento dei macroinvertebrati e` stato effettuato utilizzando due diversi metodi di raccolta: i substrati artificiali e il retino immanicato standard. Gli organismi sono stati classificati in unita` sistematiche, e si e` analizzata la loro distribuzione lungo il corso d`acqua. Inoltre sono stati calcolati i valori degli indici biotici I.B.E. (Indice Biotico Esteso) utilizzando i dati ottenuti con le due metodologie di campionamento. L`uso di substrati artificiali in ogni stazione di campionamento e` stato utile anche per stabilire il tipo di colonizzazione, l`abbondanza e le biomasse degli individui appartenenti ai vari gruppi trofici. I nostri

  20. The structure and dynamic properties of the complete histidine phosphotransfer domain of the chemotaxis specific histidine autokinase CheA from Thermotoga maritima

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Anh; Hamel, Damon J.; Zhou Hongjun; Dahlquist, Frederick W., E-mail: dahlquist@chem.ucsb.edu [University of California Santa Barbara, Department of Chemistry and Biochemistry (United States)

    2011-09-15

    The bacterial histidine autokinase CheA contains a histidine phosphotransfer (Hpt) domain that accepts a phosphate from the catalytic domain and donates the phosphate to either target response regulator protein, CheY or CheB. The Hpt domain forms a helix-bundle structure with a conserved four-helix bundle motif and a variable fifth helix. Observation of two nearly equally populated conformations in the crystal structure of a Hpt domain fragment of CheA from Thermotoga maritima containing only the first four helices suggests more mobility in a tightly packed helix bundle structure than previously thought. In order to examine how the structures of Hpt domain homologs may differ from each other particularly in the conformation of the last helix, and whether an alternative conformation exists in the intact Hpt domain in solution, we have solved a high-resolution, solution structure of the CheA Hpt from T. maritima and characterized the backbone dynamics of this protein. The structure contains a four-helix bundle characteristic of histidine phosphotransfer domains. The position and orientation of the fifth helix resembles those in known Hpt domain crystal and solution structures in other histidine kinases. The alternative conformation that was reported in the crystal structure of the CheA Hpt from T. maritima missing the fifth helix is not detected in the solution structure, suggesting a role for the fifth helix in providing stabilizing forces to the overall structure.

  1. Studio di metaboliti secondari provenienti da specie vegetali che agiscono sul SNC

    OpenAIRE

    Bracci, Antonio

    2011-01-01

    2008 - 2009 L’utilizzo delle piante medicinali nasce con l’uomo. Lo studio delle basi scientifiche a supporto del loro utilizzo si è sviluppato e continua a svilupparsi da poco più di un secolo. Lo scopo di questo lavoro di dottorato è di dare supporto all’utilizzo di specie vegetali applicabili in ambito farmacologico per curare determinate affezioni del Sistema Nervoso Centrale derivanti da patologie o dall’uso di sostanze stupefacenti. Molto spesso le sostanze vegetali...

  2. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  3. La competitività delle imprse manufatturiere statunitensi. (The competitive position of U.S. manufacturing firms

    Directory of Open Access Journals (Sweden)

    R.E. LIPSEY

    2013-12-01

    Full Text Available Con l'alto valore costante del dollaro recentemente siè verificata la  preoccupazione per l' impatto a lungo termine sulla competitività dei produttori statunitensi. Questo studio distingue tra la competitività delle imprese statunitensi ed i vantaggi degli Stati Uniti come una base di produzione . Si è constatato che , anche se la quota statunitense del commercio mondiale è diminuita a partire dai primi anni 1970, la quota detenuta da imprese americane, al contrario di imprese che producono negli Stati Uniti, è aumentato. Si sostiene che le multinazionali statunitensi hanno superato il calo del vantaggio comparativo degli Stati Uniti come base di produzione spostando all'estero.With the continuing high value of the dollar there has recently been concern over the long-term impact on the competitiveness of US manufacturers. This study distinguishes between the competitiveness of US firms and the advantages of the United States as a production base. It is found that, although the US share of world trade has declined since the early 1970s, the share held by US firms, as opposed to firms producing in the United States, has increased. It is argued that US multinationals have overcome the decline in the comparative advantage of the United States as a production base by moving abroad.JEL: F23, L60

  4. The Crèche and School structure of the CERN Staff Association is looking for a new name

    CERN Multimedia

    Staff Association

    2018-01-01

    The CERN Staff Association is launching a competition to find a new name to replace the current acronym EVEE (Espace de Vie Enfantine et École). The competition is open to everyone from Thursday, 1 February 2018 to Thursday, 15 March. All participants can send their name suggestions via the form available on the websites of the Staff Association and the Crèche and School. Good luck to all – may the best one win! P.S. The Rules of the Competition are available on both websites

  5. Retóricas del Che muerto: entre la información y significación

    OpenAIRE

    Cossia, Lautaro

    2012-01-01

    [es] Este trabajo propone comparar el uso de una misma imagen como estrategias de cierre organizadas sobre diferentes materias significantes: el rostro congelado de Ernesto Che Guevara con que culmina la película “La hora de los hornos”, obra de Octavio Getino y Fernando Solanas estrenada en Italia en 1968, y la imagen del guerrillero asesinado en la viñeta final de la historieta “La vida del Che”, biografía dibujada de Héctor ...

  6. Ordering at Si(111)/o-Si and Si(111)/SiO2 Interfaces

    DEFF Research Database (Denmark)

    Robinson, I. K.; Waskiewicz, W. K.; Tung, R. T.

    1986-01-01

    X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(111)/a-Si and Si(111)/SiO2 examples there are features in the perpendicular-momentum-transfer dependence which are not expec......X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(111)/a-Si and Si(111)/SiO2 examples there are features in the perpendicular-momentum-transfer dependence which...... are not expected from an ideal sharp interface. The diffraction profiles are explained by models with partially ordered layers extending into the amorphous region. In the Si(111)/a-Si case there is clear evidence of stacking faults which are attributed to residual 7×7 reconstruction....

  7. Caenorhabditis elegans semi-automated liquid screen reveals a specialized role for the chemotaxis gene cheB2 in Pseudomonas aeruginosa virulence.

    Directory of Open Access Journals (Sweden)

    Steven Garvis

    2009-08-01

    Full Text Available Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections in a variety of animal and plant hosts. Caenorhabditis elegans is a simple model with which one can identify bacterial virulence genes. Previous studies with C. elegans have shown that depending on the growth medium, P. aeruginosa provokes different pathologies: slow or fast killing, lethal paralysis and red death. In this study, we developed a high-throughput semi-automated liquid-based assay such that an entire genome can readily be scanned for virulence genes in a short time period. We screened a 2,200-member STM mutant library generated in a cystic fibrosis airway P. aeruginosa isolate, TBCF10839. Twelve mutants were isolated each showing at least 70% attenuation in C. elegans killing. The selected mutants had insertions in regulatory genes, such as a histidine kinase sensor of two-component systems and a member of the AraC family, or in genes involved in adherence or chemotaxis. One mutant had an insertion in a cheB gene homologue, encoding a methylesterase involved in chemotaxis (CheB2. The cheB2 mutant was tested in a murine lung infection model and found to have a highly attenuated virulence. The cheB2 gene is part of the chemotactic gene cluster II, which was shown to be required for an optimal mobility in vitro. In P. aeruginosa, the main player in chemotaxis and mobility is the chemotactic gene cluster I, including cheB1. We show that, in contrast to the cheB2 mutant, a cheB1 mutant is not attenuated for virulence in C. elegans whereas in vitro motility and chemotaxis are severely impaired. We conclude that the virulence defect of the cheB2 mutant is not linked with a global motility defect but that instead the cheB2 gene is involved in a specific chemotactic response, which takes place during infection and is required for P. aeruginosa pathogenicity.

  8. “Altrove che nella verità?”. Filosofia, scienza e vita nel pensiero di Georges Canguilhem

    Directory of Open Access Journals (Sweden)

    Daniele Poccia

    2011-10-01

    Full Text Available Secondo Georges Canguilhem non c’è verità se non quella prodotta e non scoperta dalla scienza. È il valore stesso della filosofia ad essere “altrove che nella verità”. Questo valore non veritativo risiede forse, per il pensatore francese, in qualcosa che egli definisce come un senso o un concetto iscritto materialmente nella vita. È il vivente stesso, quel vivente di cui la scienza in quanto ricerca della verità è a sua volta una semplice espressione, a contenere il concetto, o meglio, ad essere il movimento stesso della concettualizzazione. “Elsewherethan in the truth?” Philosophy, science and life in Georges Canguilhem'sthought. Accordingto Georges Canguilhem thereis no truththan the oneyieldedbutnotdiscoveredby science. Being “Elsewherethan in the truth” is the valueitselfofphilosophy”. For the Frenchthinker, this no truthfulvaluemaylie in somethinghedefines a sense or conceptmateriallywritten in the life. It's the living phenomenaitself, ofwhich science assearchfor the truthis at sametime a simpleexpression, thatcontains the concept or evenbetter, thatis the movementofconceptualization.

  9. La aventura de los bustos de Eva by Carlos Gamerro: Initiatory trip without initiation or Che lives (in a country

    Directory of Open Access Journals (Sweden)

    Juan Ezequiel Rogna

    2017-03-01

    Full Text Available Our study proposes a critical approach to La aventura de los bustos de Eva (The Adventure of the Busts of Eva, 2004, the fourth novel by Argentinian writer Carlos Gamerro, in light of the othernesses born to the Justicialist Nationalist Movement around the mid-1970s. As we understand it, the historical-literary revision put forward by this author may be spotlighted not only through his unique use of a humorous register, but also through an analysis focusing on the configuration of the Revolutionary Tendency centered around the taxonomy of an “us” and a “them” outlined by Eva Perón in Mi mensaje (My Message, 1952. Starting from that point, we will follow the “initiation journey with no initiation” made by Ernesto Marroné, the protagonist of the novel diptych made up of La aventura... and Un yuppie en la columna del Che Guevara (A Yuppie at the Column of Che Guevara, 2011. We will particularly stop by the character’s subjective universe and his patent tension between two legacies, a biological one and an adoptive one, so as to look at possible convergences and/or divergences of literate vs illiterate, or high-brow vs low-brow, cultural paradigms (which in our country have come to be matched to different racial modalities and political projects, on this journey that will go through epiphany, revelation, deception, and treason.

  10. «Che si riduca al modo di procedere di Castiglia». El debate sobre el procedimiento inquisitorial portugués en tiempos de los Austrias

    Directory of Open Access Journals (Sweden)

    López-Salazar Codes, Ana Isabel

    2007-06-01

    Full Text Available At the time of the Dynastic Union the Portuguese cristãos-novos and his supporter send constant petitions to the Catholics Monarchs and at the Holy Father to obtain the reformation of the behaviour of the Portuguese Inquisition. Beyond of the concrete aspects, the cristãos-novos search to obtaining the introduction in Portugal the proceedings of the Spanish Inquisition. A great deal of the controversy remains balanced at the validity of the singular witness for the crime of heresy. For is part, the Portuguese Holy Office fight, for the sixty years, to maintain his autonomy and jurisdiction to the intromissions of the Crown and the Holy Siege.Durante la Unión Dinástica los cristãos-novos portugueses y sus valedores elevaron constantes súplicas los monarcas católicos y a los sumos pontífices para que reformasen el modo de proceder de la Inquisición portuguesa. Por encima de los aspectos concretos, los cristãos-novos trataron de conseguir que se introdujese en Portugal el procedimiento de la Inquisición española. La controversia quedó, en gran medida, centrada en la validez de los testigos singulares para probar el crimen de herejía. Por su parte, el Santo Oficio luso pugnó, durante los sesenta años, para mantener su autonomía y jurisdicción frente a las intromisiones de la Corona o de la Santa Sede.

  11. The Huguenot identity in 19th century music: The "Sechs Sprüche zum Kirchenjahr" by Felix Mendelssohn

    Directory of Open Access Journals (Sweden)

    Robert Weeda

    2012-01-01

    Full Text Available Hierdie artikel gaan oor die komponiste Felix Mendelssohn en Giacomo Meyerbeer. Meyerbeer die komponis van die opera Les Huguenots, en Mendelssohn, 'n Jood wat 'n "Calvinis" geword het. Meyerbeer vertel in die opera (1836, geanker aan die Lutherse melodie "'n Vaste Burg is onse God" die verhaal van die Bartolomeusnagmoorde. Mendelssohn, 'n bekeerling tot die sg Hugenote-religie, verwoord sy opregte geloof gedurende die jare 1843-1846 in die voortreflike musikaleuitdrukkings Sechs Sprüche zum Kirchenjahr (Ses Spreuke vir die Kerkjaar wat opgeneem is in die gereformeerde liturgie vir die Brandenburg gemeente. Op 'n bepaalde manier vertel albei komponiste ons iets van die Hugenote-identiteit in die negentiende-eeuse musiek.

  12. Forensic identification of skeletal remains from members of Ernesto Che Guevara's guerrillas in Bolivia based on DNA typing.

    Science.gov (United States)

    Lleonart, R; Riego, E; Saínz de la Peña, M V; Bacallao, K; Amaro, F; Santiesteban, M; Blanco, M; Currenti, H; Puentes, A; Rolo, F; Herrera, L; de la Fuente, J

    2000-01-01

    We report the positive identification of several members of the guerrillas led by Ernesto "Che" Guevara on the 1960 s in Bolivia by means of DNA fingerprinting. Successful DNA typing of both short tandem repeat loci and the hypervariable region of the human mitochondrial DNA was achieved after extracting total DNA from bones obtained from two burial sites. Given the size of the Cuban database for the STR allele frequencies, a conservative approach was followed to estimate the statistical significance of the genetic evidence. The estimated probabilities of paternity for the two cases in which the paternity logic was applied were higher than 99%. One case was analyzed using mitochondrial DNA and could not be excluded from the identity proposed by the forensic anthropology team. A fourth case was identified by exclusion, on the basis of the positive identification of the other remains, the historical and other anthropological evidence.

  13. [Textual research on Han-Chinese formulae collected in Tubo medical manuscript unearthed in 'Bum-pa-Che Tower].

    Science.gov (United States)

    Liu, Y H; Nong, H C

    2016-11-28

    A Tibetan manuscript with title of Sman-dpyad gces-pa grub-pa kun-'dus-pa in the Collection of Practiced Medical Quintessence, was found in the basement of a Buddhist tower named 'Bum-pa-che in Lhokha (Shannan), Tibet. It contains a purgative recipe of TCM with its title "Powder of Han Region" and several ingredients in Chinese transliteration. Based upon the rule of medieval Chinese system of pronunciation with reference of related texts and studies, a textual research identifies it as a kind of Maren (seed of Cannabis sativa L. ) wan in TCM. Although no identical formulae of its kind has been found in extant literature of TCM prior to the Song Dynasty(960 AD), yet its ingredients, pharmaceutical preparation and efficacy are very similar to the Modified maren wan, the variant formulae of Maren wan in Wai tai mi yao (Arcane Essentials from the Imperial Library) of the Tang Dynasty.

  14. Retóricas del Che muerto: entre la información y significación

    Directory of Open Access Journals (Sweden)

    Cossia, Lautaro

    2012-01-01

    Full Text Available [es] Este trabajo propone comparar el uso de una misma imagen como estrategias de cierre organizadas sobre diferentes materias significantes: el rostro congelado de Ernesto Che Guevara con que culmina la película “La hora de los hornos”, obra de Octavio Getino y Fernando Solanas estrenada en Italia en 1968, y la imagen del guerrillero asesinado en la viñeta final de la historieta “La vida del Che”, biografía dibujada de Héctor Oesterheld y Alberto Breccia publicada ese mismo año. Dicho recorte analítico tiene el propósito de observar las gramáticas visuales puestas en juego en el marco de un proceso histórico que reconoce nuevos modos de socialización del arte y un contorno político que carga de significados la resolución de ambas obras. [en] This paper proposes to compare the use of the same image as strategies of closure organized on different “significant materials”: the frozen face of Ernesto Che Guevara with which the film “The Hour of the Furnaces” ends, movie of Fernando Solanas and Octavio Getino that was released in Italy in 1968, and the image of the murdered “guerrillero” in the final vignette of the comic “The life of Che”, biography drawn by Hector Oesterheld and Alberto Breccia and published the same year. This selection in the analysis proposes to observe the “visual grammars” that have played in the framework of one historical process which recognizes new manners of socialization of art and a political outline that charge of meanings the resolution of both works.

  15. Louis Blajan, Dottore in Medicina Veterinaria: Il dinamico veterinario che seppe traghettare l’Organizzazione Mondiale per la Sanità Animale (Office International des Épizooties: OIE nel mondo moderno

    Directory of Open Access Journals (Sweden)

    Anon.

    2010-03-01

    Full Text Available Nato il 10 aprile 1924 a Lahage (nell’Alta Garonna, in Francia, Louis Blajan si è spento lo scorso 10 febbraio 2010 a Mont-de-Marsan.Dopo aver frequentato il Lycée Pierre de Fermat di Tolosa, nel 1948 Louis completa gli studi presso la Scuola di Veterinaria di Tolosa. Nel 1949, si diploma all’Institut d’élevage et de médecine vétérinaire des pays tropicaux (IEMVT e dal 1949 al 1952 è nel territorio d’oltremare francese del Mali. Tornato in Francia, dal 1953 al 1968 Louis esercita come veterinario di Stato presso il Ministero dell’Agricoltura, responsabile per l’afta epizootica, la peste suina e la malattia di Newcastle, nonché come Presidente del Comitato consultivo per le malattie infettive. In seguito, viene nominato Ispettore capo veterinario e Responsabile per la politica di controllo delle frontiere.Nel 1952, Louis sposa Janine, moglie affezionata che lo appoggia con ardore in ogni fase della sua carriera e perde la vita in un incidente un mese prima che il marito vada in pensione nel 1990.Dal 1968 al 1977, Louis è Direttore tecnico di Cofranimex (Compagnie Française pour l’importation et l’exportation des animaux reproducteurs et leur semence e dal 1977 al 1978 riveste il ruolo di Direttore dell’Association pour le développement des techniques de l’élevage français (ADETEF.Louis entra a lavorare nell’Office International des Épizooties (oggi noto come Organizzazione Mondiale per la Sanità Animale o ‘OIE’ dove, dal 1978 al 1980, occupa la posizione di Direttore del Dipartimento tecnico. Due anni più tardi, nel 1980, viene eletto Direttore Generale, coronando il sogno di ogni professionista della medicina veterinaria e raggiungendo l’apice della propria carriera. Rieletto nel 1985, si ritira dalla vita lavorativa nel 1990.Durante gli anni in cui fu a capo dell’OIE, Louis seppe trasformare quella che all’epoca era una struttura antiquata in un’organizzazione internazionale moderna ed

  16. TIME COURSE AND DOSE RESPONSE ASSESSMENT OF CHOLINESTERASE (CHE) INHIBITION IN ADULT RATS TREATED ACUTELY WITH CARBARYL, METHOMYL, METHIOCARB, OXAMYL, OR PROPOXUR.

    Science.gov (United States)

    To compare the toxicity of 5 N-methyl carbamates, the time course and dose response profiles for ChE inhibition were established for each. For the time course comparison, adult male Long Evans rats (n=5 dose group) were dosed orally with either carbaryl (CB; 30 mg/kg in corn oi...

  17. Negotiating and Appropriating the "One Person, One Language" Policy within the Complex Reality of a Multilingual Crèche in Strasbourg

    Science.gov (United States)

    Caporal-Ebersold, Eloise; Young, Andrea

    2016-01-01

    The aim of this article is to analyse the early childhood education and care (ECEC) language policy in the city of Strasbourg, focusing on an ethnographic case study of a newly established bilingual English-French crèche in the city. In France, establishing an early childhood education structure--more specifically, a day care centre catering to…

  18. Relative roles of the fla/che P(A), P(D-3), and P(sigD) promoters in regulating motility and sigD expression in Bacillus subtilis.

    Science.gov (United States)

    West, J T; Estacio, W; Márquez-Magaña, L

    2000-09-01

    Three promoters have been identified as having potentially important regulatory roles in governing expression of the fla/che operon and of sigD, a gene that lies near the 3' end of the operon. Two of these promoters, fla/che P(A) and P(D-3), lie upstream of the >26-kb fla/che operon. The third promoter, P(sigD), lies within the operon, immediately upstream of sigD. fla/che P(A), transcribed by E sigma(A), lies >/=24 kb upstream of sigD and appears to be largely responsible for sigD expression. P(D-3), transcribed by E sigma(D), has been proposed to participate in an autoregulatory positive feedback loop. P(sigD), a minor sigma(A)-dependent promoter, has been implicated as essential for normal expression of the fla/che operon. We tested the proposed functions of these promoters in experiments that utilized strains that bear chromosomal deletions of fla/che P(A), P(D-3), or P(sigD). Our analysis of these strains indicates that fla/che P(A) is absolutely essential for motility, that P(D-3) does not function in positive feedback regulation of sigD expression, and that P(sigD) is not essential for normal fla/che expression. Further, our results suggest that an additional promoter(s) contributes to sigD expression.

  19. RESISTENCIA MICROBIANA EN EL CARDIOCENTRO ERNESTO CHE GUEVARA. ESTUDIO DE 5 AÑOS / Microbial resistance at the “Ernesto Che Guevara” Cardiology Hospital. A five year study

    Directory of Open Access Journals (Sweden)

    Nérida Rodríguez Oliva

    2009-06-01

    Full Text Available Introduction and Objectives: The appearance of nosocomial bacterial resistance represents a problem of growing concern because it largely affects the evolution of patients and the health resources devoted to it. The objective of this work was to determine the most common germs and their microbial resistance. Methods: A descriptive retrospective study was carried out analyzing the result of the isolation of germs from all type of secretions and from the blood cultures of a group ofpatients hospitalized at the Ernesto Che Guevara Cardiology Hospital in a five year period. Results: A total of 397 strains were isolated, 77 Staphylococcus aureus and 320 Enterobacteriaceae. The former presented 100% resistance to penicillin. The Staphylococcus sensitive to methicillin presented 4.9 % resistance to cotrimoxazole and gentamicin. The strains resistant to methicillin or oxacillin had a high resistance to gentamicin (87.5 % and ciprofloxacin (81.2 %, a medium resistance to cefazolin and oxacilline (20.5 %, and just 12.5 percent resistance to cotrimoxazole. Conclusions: the Staphylococcus aureus and the Enterobacteriaceae were the most common germs. The preoperative prophylaxis in these patients must not be done with cefazolin as a routine because the staphylococci resistant to methicillin or oxacillin have influence on other antimicrobials.

  20. How to organize a maths e-book for vocational training schools

    Directory of Open Access Journals (Sweden)

    Damiano Trombini

    2016-04-01

    Full Text Available This paper aims to examine the educational planning in order to realize a maths e-book which might be used by teachers in vocational training schools. Along with the analysis of the advantages and the efficiency that a teacher could obtain adopting this type of multimedia technology, this paper will also analyze how to organize and insert into an e-book resources which allow to implement instructional strategies such as flipped classroom, cooperative learning, peer tutoring and all the aspects relating to the learning evaluation. Come organizzare un e-book per l’insegnamento della matematica nelle classi prime di istituti ad indirizzo professionaleLo scopo di questo saggio è quello di esaminare la progettazione didattica per la realizzazione di un e-book per l’insegnamento della matematica nelle classi prime di istituti secondari di secondo grado ad indirizzo professionale. Unitamente all’analisi dei vantaggi e dell’efficacia che un docente potrebbe ottenere nell’avvalersi di questo tipo di tecnologia multimediale, si analizzeranno le modalità di organizzazione e inserimento nell’e-book di risorse che permettano di implementare strategie didattiche come la flipped classroom, cooperative learning e il peer tutoring, nonché gli aspetti che riguardano la valutazione dell’apprendimento.

  1. E-learning e Università. Riflessioni tratte dalle interviste a quattro esperti italiani: Antonio Calvani, Luigi Guerra, Roberto Maragliano, Pier Cesare Rivoltella.

    OpenAIRE

    Laura Corazza

    2006-01-01

    Quattro esperti italiani di e-learning in ambito universitario hanno accettato di rispondere ad alcune domande su vantaggi e svantaggi, caratteristiche attuali e prospettive future di una nuova forma di didattica, l’e-learning, che richiede un ripensamento complessivo del modo di intendere l’apprendimento, lo sviluppo del sapere e la formazione della conoscenza.

  2. SI - Small Scale Advantages

    OpenAIRE

    Nordström, Marie; Kallin Westin, Lena

    2006-01-01

    Not being part of a larger SI-organisation has both advantages and disadvantages. In this paper we try to illustrate the advantages of doing SI small scale. In a large scale SI-organisation the supervisors are often not teachers themselves and/or not familiar with the practices of a specific course. To have teaching staff supervising a SIproject completely focused on one course is favourable in many ways. The decision to introduce SI was taken by the department of Computing Science to support...

  3. Advantages of the WRAIR whole blood cholinesterase assay: comparative analysis to the micro-Ellman, Test-mate ChE, and Michel (DeltapH) assays.

    Science.gov (United States)

    Haigh, Julian R; Lefkowitz, Lee J; Capacio, Benedict R; Doctor, Bhupendra P; Gordon, Richard K

    2008-09-25

    Red blood cell AChE (RBC-AChE) and plasma BChE can be used as sensitive biomarkers to detect exposure to OP nerve agents, pesticides, and cholinergic drugs. In a comparative study, RBC-AChE and serum BChE activities in whole blood was obtained from forty seven healthy male and female human volunteers, and then exposed separately ex vivo to three OP nerve agents (soman (GD), sarin (GB) and VX) to generate a wide range of inhibition of AChE and BChE activity (up to 90% of control). These samples were measured using four different ChE assays: (i) colorimetric microEllman (using DTNB at 412 nm), (ii) Test-mate ChE field kit (also based on the Ellman assay), (iii) Michel (delta pH), and (iv) the Walter Reed Army Institute of Research Whole Blood (WRAIR WB) cholinesterase assay. The WRAIR assay is a modified Ellman method using DTP at 324 nm (which minimizes hemoglobin interference and improves sensitivity), and determines AChE and BChE in a small whole blood sample simultaneously. Scatter plots of RBC-AChE activities were determined using the WRAIR ChE assay versus the micro-Ellman, Test-mate and Michel after exposure to varying concentrations of soman, sarin and VX. Regression analyses yielded mostly linear relationships with high correlations (r2 = 0.83-0.93) for RBC-AChE values in the WRAIR assay compared to the alternate methods. For the plasma BChE measurements, individual human values were significantly more variable (as expected), resulting in lower correlations using WRAIR ChE versus the alternate assays (r2 values 0.5 - 0.6). To circumvent the limitations of simple correlation analysis, Bland and Altman analysis for comparing two independent measurement techniques was performed. For example, a Bland and Altman plot of the ratio of the WRAIR whole blood AChE and Michel AChE (plotted on the y-axis) vs. the average of the two methods (x-axis) shows that the majority of the individual AChE values are within +/- 1.96 S.D. of the mean difference, indicating that the

  4. AATF/Che-1 acts as a phosphorylation-dependent molecular modulator to repress p53-driven apoptosis.

    Science.gov (United States)

    Höpker, Katja; Hagmann, Henning; Khurshid, Safiya; Chen, Shuhua; Hasskamp, Pia; Seeger-Nukpezah, Tamina; Schilberg, Katharina; Heukamp, Lukas; Lamkemeyer, Tobias; Sos, Martin L; Thomas, Roman K; Lowery, Drew; Roels, Frederik; Fischer, Matthias; Liebau, Max C; Resch, Ulrike; Kisner, Tülay; Röther, Fabian; Bartram, Malte P; Müller, Roman Ulrich; Fabretti, Francesca; Kurschat, Peter; Schumacher, Björn; Gaestel, Matthias; Medema, René H; Yaffe, Michael B; Schermer, Bernhard; Reinhardt, H Christian; Benzing, Thomas

    2012-10-17

    Following genotoxic stress, cells activate a complex signalling network to arrest the cell cycle and initiate DNA repair or apoptosis. The tumour suppressor p53 lies at the heart of this DNA damage response. However, it remains incompletely understood, which signalling molecules dictate the choice between these different cellular outcomes. Here, we identify the transcriptional regulator apoptosis-antagonizing transcription factor (AATF)/Che-1 as a critical regulator of the cellular outcome of the p53 response. Upon genotoxic stress, AATF is phosphorylated by the checkpoint kinase MK2. Phosphorylation results in the release of AATF from cytoplasmic MRLC3 and subsequent nuclear translocation where AATF binds to the PUMA, BAX and BAK promoter regions to repress p53-driven expression of these pro-apoptotic genes. In xenograft experiments, mice exhibit a dramatically enhanced response of AATF-depleted tumours following genotoxic chemotherapy with adriamycin. The exogenous expression of a phospho-mimicking AATF point mutant results in marked adriamycin resistance in vivo. Nuclear AATF enrichment appears to be selected for in p53-proficient endometrial cancers. Furthermore, focal copy number gains at the AATF locus in neuroblastoma, which is known to be almost exclusively p53-proficient, correlate with an adverse prognosis and reduced overall survival. These data identify the p38/MK2/AATF signalling module as a critical repressor of p53-driven apoptosis and commend this pathway as a target for DNA damage-sensitizing therapeutic regimens.

  5. Atomistic structural ensemble refinement reveals non-native structure stabilizes a sub-millisecond folding intermediate of CheY

    Science.gov (United States)

    Shi, Jade; Nobrega, R. Paul; Schwantes, Christian; Kathuria, Sagar V.; Bilsel, Osman; Matthews, C. Robert; Lane, T. J.; Pande, Vijay S.

    2017-03-01

    The dynamics of globular proteins can be described in terms of transitions between a folded native state and less-populated intermediates, or excited states, which can play critical roles in both protein folding and function. Excited states are by definition transient species, and therefore are difficult to characterize using current experimental techniques. Here, we report an atomistic model of the excited state ensemble of a stabilized mutant of an extensively studied flavodoxin fold protein CheY. We employed a hybrid simulation and experimental approach in which an aggregate 42 milliseconds of all-atom molecular dynamics were used as an informative prior for the structure of the excited state ensemble. This prior was then refined against small-angle X-ray scattering (SAXS) data employing an established method (EROS). The most striking feature of the resulting excited state ensemble was an unstructured N-terminus stabilized by non-native contacts in a conformation that is topologically simpler than the native state. Using these results, we then predict incisive single molecule FRET experiments as a means of model validation. This study demonstrates the paradigm of uniting simulation and experiment in a statistical model to study the structure of protein excited states and rationally design validating experiments.

  6. Si deve amare la mamma anche se povera’. The Dante Alighieri Society, Italian emigration and the safeguarding of italianità, 1870-1925

    Directory of Open Access Journals (Sweden)

    Tamara van Kessel

    2012-05-01

    Full Text Available Si deve amare la mamma anche se povera’.  La Società Dante Alighieri, l’emigrazione italiana e la protezione dell’italianità all’estero, 1870-1925L’attività della Società Dante Alighieri per la tutela degli emigrati italiani agli inizi del Novecento dimostra quanto erano intrecciati la costruzione dell’identità nazionale ed il desiderio di mantenere i legami con gli italiani all’estero. Benché nell’Italia unita ci fossero state diverse opinioni sul fenomeno dell’emigrazione di massa, il governo cominciò a vedere questi concittadini sparsi per il mondo non come segno di povertà, ma come un veicolo per comprovare all’estero le doti attribuite al proprio paese. In un simile spirito nazionalista, la Dante si occupò di fare dell’emigrato un degno rappresentate della cultura e società italiane. Un esempio di come cercarono di guidare l’emigrato è ‘Il Decalogo degli Emigranti’: un documento divulgato tramite il bollettino della Dante nel 1925. Si direbbe che le raccomandazioni di questo ‘Decalogo’si inseriscono armoniosamente nella propaganda fascista di quell’epoca. Un documento simile del 1913 fa vedere invece come già allora era invocata una forte lealtà alla nazione. Ciò che colpisce nelle due fonti è che l’italiano all’estero veniva incoraggiato a consumare prodotti esclusivamente italiani. Questo motivo economico era parte integrante di molta della politica culturale internazionale di quel periodo. Infine, la forma scelta – quella del decalogo – è emblematica per il modo in cui si dovette ricorrere ai modelli religiosi per consolidare l’identità italiana laica.

  7. Effects of Kapton Sample Cell Windows on the Detection Limit of Smectite: Implications for CheMin on the Mars Science Laboratory Mission

    Science.gov (United States)

    Achilles, C. N.; Ming, Douglas W.; Morris, R. V.; Blake, D. F.

    2012-01-01

    The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity is an X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of providing the mineralogical and chemical compositions of rocks and soils on the surface of Mars. CheMin uses a microfocus X-ray tube with a Co target, transmission geometry, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. CheMin has two different window materials used for sample cells -- Mylar and Kapton. Instrument details are provided elsewhere. Fe/Mg-smectite (e.g., nontronite) has been identified in Gale Crater, the MSL future landing site, by CRISM spectra. While large quantities of phyllosilicate minerals will be easily detected by CheMin, it is important to establish detection limits of such phases to understand capabilities and limitations of the instrument. A previous study indicated that the (001) peak of smectite at 15 Ang was detectable in a mixture of 1 wt.% smectite with olivine when Mylar is the window material for the sample cell. Complications arise when Kapton is the window material because Kapton itself also has a diffraction peak near 15 Ang (6.8 deg 2 Theta). This study presents results of mineral mixtures of smectite and olivine to determine smectite detection limits for Kapton sample cells. Because the intensity and position of the smectite (001) peak depends on the hydration state, we also analyzed mixtures with "hydrated" and "dehydrated"h smectite to examine the effects of hydration state on detection limits.

  8. Department of Che

    African Journals Online (AJOL)

    USER

    2015-03-26

    Mar 26, 2015 ... breathe in air and out, enhance respiration in living ... Soil serves as the main sources of trace and toxic elements for plant as a micronutrients and as well as pollutants. (Rind et al., 2013). Sediment particles are made up of materials derived from rock, soil and anthropogenic sources (Okoro et al., 2014).

  9. Department of Che

    African Journals Online (AJOL)

    USER

    2015-03-26

    Mar 26, 2015 ... The ma or parameters investigated on analysis include heavy metals ... copper are the predominant metals in the samples while chromium was not detected at some of the sampled .... after collection in the laboratory. The.

  10. Manufacture and properties of Si-SiC-MoSi sub 2 composites. Herstellung und Eigenschaften von Si-SiC-MoSi sub 2 -Verbundwerkstoffe

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, W.; Wruss, W.; Stroh, R.; Lux, B. (Technische Univ., Vienna (Austria). Inst. fuer Chemische Technologie Anorganischer Stoffe); Ekstroem, T. (SANDVIK Hard Materials AB, Stockholm (Sweden))

    1990-06-01

    This report deals with the manufacture of SiC-Si-MoSi{sub 2} composites, i.e. with modified SiSiC composites. The scope of application of SiSiC is limited by the melting temperature of silicon ({approx equal} 1420deg C) and by the chemical resistance of the silicon binder phase with respect to the surrounding medium. The application temperature can be raised and the corrosion resistance improved by replacing the silicon matrix with refractory silicides, e.g. molybdenum disilicide. The free silicon composite was partially replaced with molybdenum disilicide by infiltrating an SiC-C green compact with the Si-Mo melt. The insertion of the new phase reduces the room-temparture strength from 323 MPa for the unalloyed SiSiC (density: 2.83 g/cm{sup 3}, 42.7 vol.% silicon) to 171 MPa (density: 3.05 g/cm{sup 3}, 5.8 vol.% MoSi{sub 2}, referred to the silicon binder). However, the high-temperature properties of the altered material are expected to be improved via ductilization of MoSi{sub 2} at {approx equal} 1000deg C. (orig.).

  11. La sostenibilità finanziaria della cultura. Il caso delle istituzioni teatrali italiane / The financial sustainability of culture. The case of Italian theatres

    Directory of Open Access Journals (Sweden)

    Pier Luigi Sacco

    2011-12-01

    Full Text Available Il dibattito tra sostenitori del finanziamento pubblico all’arte e alla cultura e suoi oppositori ha origini lontane, ma mai come in questi mesi ha assunto un interesse così profondo, in funzione di un fondamentale trade-off che si acuisce sempre più: la restrizione dei budget di spesa a disposizione degli Stati occidentali da un lato, e i benefici sempre più marcati, anche di natura economica, che nuovi studi sembrano attribuire agli investimenti in arte e cultura dall’altro. Tramite un’analisi effettuata sui principali teatri italiani in termini di ricavi generati, il paper comprova l’impossibilità per le istituzioni culturali di potere conciliare in modo autonomo la propria mission di fondo con principi di sostenibilità finanziaria. Gli autori sostengono che il supporto al settore cultura rappresenta attualmente un’attività imprescindibile per uno Stato, non solo in funzione del carattere di meritorietà del bene culturale, ma soprattutto alla luce anche dei vantaggi di tipo economico, fino a pochi anni fa trascurati o meglio, difficilmente quantificabili, che la cultura è in grado di apportare per l’economia del «Sistema Paese»; vantaggi la cui quantificazione sarà possibile grazie al rapido sviluppo di metodologie valutative di prossima utilizzabilità.   Debates between advocates of public financing to arts and culture and its opponents have far-off roots, but they never gained such an importance like in these months, because of a crucial trade-off that has been exacerbating more and more: from the one hand, budget allowance restrictions available to Western States; on the other hand, the even more marked benefits – also in economic terms – that new studies attribute to investments in arts and culture. Through an analysis conducted on the main Italian theatres as for ticket sales, the paper proves the impossibility for the cultural institutions to mesh autonomously their main mission with financial sustainability

  12. Structural studies of conformational changes of proteins upon phosphorylation: Structures of activated CheY, CheY-N16-FliM complex, and AAA + ATPase domain of NtrC1 in both inactive and active states

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seok-Yong [Univ. of California, Berkeley, CA (United States)

    2003-04-10

    Protein phosphorylation is a general mechanism for signal transduction as well as regulation of cellular function. Unlike phosphorylation in eukaryotic systems that uses Ser/Thr for the sites of modification, two-component signal transduction systems, which are prevalent in bacteria, archea, and lower eukaryotes, use an aspartate as the site of phosphorylation. Two-component systems comprise a histidine kinase and a receiver domain. The conformational change of the receiver domain upon phosphorylation leads to signal transfer to the downstream target, a process that had not been understood well at the molecular level. The transient nature of the phospho-Asp bond had made structural studies difficult. The discovery of an excellent analogue for acylphosphate, BeF3-, enabled structural study of activated receiver domains. The structure of activated Chemotaxis protein Y (CheY) was determined both by NMR spectroscopy and X-ray crystallography. These structures revealed the molecular basis of the conformational change that is coupled to phosphorylation. Phosphorylation of the conserved Asp residue in the active site allows hydrogen bonding of the T87 Oγ to phospho-aspartate, which in turn leads to the rotation of Y106 into the ''in'' position (termed Y-T coupling). The structure of activated CheY complexed with the 16 N-terminal residues of FliM (N16-FliM), its target, was also determined by X-ray crystallography and confirmed the proposed mechanism of activation (Y-T coupling). First, N16-FliM binds to the region on CheY that undergoes a significant conformational change. Second, the ''in'' position of Y106 presents a better binding surface for FliM because the sidechain of Y106 in the inactive form of CheY (''out'' position) sterically interferes with binding of N16-FliM. In addition to confirmation of Y-T coupling, the structure of the activated CheY-N16-FliM complex suggested that the

  13. Scarless deletion of up to seven methyl-accepting chemotaxis genes with an optimized method highlights key function of CheM in Salmonella Typhimurium.

    Directory of Open Access Journals (Sweden)

    Stefanie Hoffmann

    Full Text Available Site-directed scarless mutagenesis is an essential tool of modern pathogenesis research. We describe an optimized two-step protocol for genome editing in Salmonella enterica serovar Typhimurium to enable multiple sequential mutagenesis steps in a single strain. The system is based on the λ Red recombinase-catalyzed integration of a selectable antibiotics resistance marker followed by replacement of this cassette. Markerless mutants are selected by expressing the meganuclease I-SceI which induces double-strand breaks in bacteria still harboring the resistance locus. Our new dual-functional plasmid pWRG730 allows for heat-inducible expression of the λ Red recombinase and tet-inducible production of I-SceI. Methyl-accepting chemotaxis proteins (MCP are transmembrane chemoreceptors for a vast set of environmental signals including amino acids, sugars, ions and oxygen. Based on the sensory input of MCPs, chemotaxis is a key component for Salmonella virulence. To determine the contribution of individual MCPs we sequentially deleted seven MCP genes. The individual mutations were validated by PCR and genetic integrity of the final seven MCP mutant WRG279 was confirmed by whole genome sequencing. The successive MCP mutants were functionally tested in a HeLa cell infection model which revealed increased invasion rates for non-chemotactic mutants and strains lacking the MCP CheM (Tar. The phenotype of WRG279 was reversed with plasmid-based expression of CheM. The complemented WRG279 mutant showed also partially restored chemotaxis in swarming assays on semi-solid agar. Our optimized scarless deletion protocol enables efficient and precise manipulation of the Salmonella genome. As demonstrated with whole genome sequencing, multiple subsequent mutagenesis steps can be realized without the introduction of unwanted mutations. The sequential deletion of seven MCP genes revealed a significant role of CheM for the interaction of S. Typhimurium with host cells

  14. Automatización del control del cálculo de extracciones en la mina de la empresa niquelera Ernesto Che Guevara

    Directory of Open Access Journals (Sweden)

    Arístides A. Legrá-Lobaina

    2010-03-01

    Full Text Available En el artículo se muestran los elementos fundamentales de un algoritmo cuyo objetivo es establecer el contenido y el orden de los procedimientos necesarios para realizar el control del cálculo de extracciones en la mina de la empresa Ernesto Che Guevara que explota, a cielo abierto, yacimientos lateríticos ferroniquelíferos en la región de Moa, Cuba. Asimismo se presenta el diseño de los diálogos informáticos que han automatizado el algoritmo en la aplicación informática Tierra.

  15. La maîtrise des risques microbiologiques liés à la viande fraîche en Belgique

    OpenAIRE

    Daube, Georges

    2000-01-01

    Nous connaissons de mieux en mieux les risques liés à la consommation de viande fraîche. Certains risques biologiques diminuent comme la yersiniose ou la brucellose ; certains semblent augmenter, telles la salmonellose ou la campylobactériose ; enfin, certains émergent, comme les syndromes hémolytiques et urémiques dus à E. coli, ou ont été récemment identifiés comme transmissibles par les aliments, comme la cryptosporidiose et la listériose. Ce tableau un peu sombre et les solutions qui se...

  16. L’emergenza dei tre lustri, la salma contesa e il gioco dell’Ultimatum. Alcune riflessioni sui problemi che caratterizzano le decisioni pubbliche in Italia

    OpenAIRE

    Villani, Salvatore

    2008-01-01

    Negli ultimi tempi, fra gli studiosi dei processi di formazione delle scelte pubbliche è in corso un interessante dibattito volto ad individuare le tecniche più appropriate per gestire in maniera efficace (ovvero in tempi rapidi e garantendo la stabilità e la durevolezza delle decisioni o degli accordi a-dottati) ed equa (il fatto che le controparti siano soddisfatte della decisione adottata o dell’accordo raggiunto costituisce una garanzia per la stabilità e la durevolezza degli stessi) i co...

  17. Promoter selectivity of the Bacillus subtilis response regulator DegU, a positive regulator of the fla/che operon and sacB.

    Science.gov (United States)

    Tsukahara, Kensuke; Ogura, Mitsuo

    2008-01-15

    The response regulator DegU and its cognate histidine kinase DegS constitute a two-component system in the Gram-positive soil bacterium Bacillus subtilis. Unphosphorylated and phosphorylated forms of DegU are known to activate target gene transcription in B. subtilis. Although phosphorylated DegU (DegU-P) regulates more than one hundred and twenty genes, the targets of unphosphorylated DegU are unknown, except for comK. We found that the fla/che (flagella and chemotaxis) operon is positively regulated by unphosphorylated DegU. The effect was most prominent in a strain bearing the functional swrAA gene, a positive regulator of fla/che. Unphosphorylated DegU bound to two regions in the fla/che regulatory region containing an inverted repeat-like sequence that resembles the inverted repeat (IR) in the comK promoter. Mutational analysis revealed that positive regulation of fla/che by SwrAA requires DegU-binding. An analysis of the DegU-P-regulated gene sacB (levansucrase gene) by footprint and mutational analyses revealed that DegU-P bound to a direct repeat (DR) of the DegU-recognition motifs, which has been shown to be functional in vivo, while unphosphorylated DegU did not. These results strongly suggest that the arrangement of the DegU-binding motifs determines whether unphosphorylated DegU or DegU-P binds to the sacB promoter. The hypothesis was confirmed by observing degS-independent expression when the DR in the sacB-lacZ fusion was changed to an IR, suggesting that unphosphorylated DegU regulates the sacB promoter through the newly created IR. This was confirmed by binding of unphosphorylated DegU to the IR in the sacB promoter. This study demonstrated that DegU positively regulates flgB and sacB through its binding to the promoter regions. We demonstrated that DegU-P prefers binding to DR but not to IR in the sacB promoter.

  18. CodY Regulates SigD Levels and Activity by Binding to Three Sites in the fla/che Operon.

    Science.gov (United States)

    Ababneh, Qutaiba O; Herman, Jennifer K

    2015-09-01

    Exponentially growing cultures of Bacillus subtilis (PY79) are composed primarily of nonmotile, chained cells. The alternative sigma factor, SigD, promotes the phenotypic switch from nonmotile, chained cells to unchained, motile cells. In the present work, we investigated the role of the GTP-sensing protein CodY in the regulation of SigD. Deletion of codY resulted in a significant increase in SigD accumulation and activity and shifted the proportion of unchained cells up from ∼15% to ∼75%, suggesting that CodY is an important regulator of SigD. CodY was previously shown to bind to the PD3 and Pfla/che promoters located upstream of the first gene in the sigD-containing fla/che operon. Using electrophoretic mobility shift assays, we found that CodY also binds to two other previously uncharacterized sites within the fla/che operon. Mutations in any one of the three binding sites resulted in SigD levels similar to those seen with the ΔcodY mutant, suggesting that each site is sufficient to tip cells toward a maximal level of CodY-dependent SigD accumulation. However, mutations in all three sites were required to phenocopy the ΔcodY mutant's reduced level of cell chaining, consistent with the idea that CodY binding in the fla/che operon is also important for posttranslational control of SigD activity. One way that bacteria adapt quickly and efficiently to changes in environmental quality is to employ global transcriptional regulators capable of responding allosterically to key cellular metabolites. In this study, we found that the conserved GTP-sensing protein CodY directly regulates cell motility and chaining in B. subtilis by controlling expression and activity of SigD. Our results suggest that B. subtilis becomes poised for cell dispersal as intracellular GTP levels are depleted. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  19. Analisi della qualità in biblioteca: la soluzione SiMonLib™@CASPUR

    Directory of Open Access Journals (Sweden)

    Ugo Contino

    2011-12-01

    Full Text Available ItLa raccolta periodica di dati e l’analisi delle performance, in un’ottica di valutazione della Qualità del Servizio, sono sicuramente elementi rilevanti per coloro che s’interessino della gestione di una biblioteca o di un sistema bibliotecario. Modi sempre più efficienti e ottimizzati per gestire specifiche campagne di raccolta dati non possono prescindere dall’uso di strumenti in ambito ICT, soprattutto per far fronte ai non banali problemi logistico organizzativi che simili attività di raccolta dati possono comportare. In quest’ambito merita sicuramente menzione SimonLib™, un software prodotto dalla XSystems di Cagliari e pensato per gestire i processi di raccolta dati e misura della qualità in biblioteca, sia essa singola o appartenente ad un sistema. Conscio delle potenzialità offerte da questa piattaforma, il CASPUR ha sottoscritto recentemente un accordo con XSystems per offrire SimonLib alla comunità delle biblioteche italiane, sia pubbliche che private. Il servizio offerto, SiMonLib@CASPUR, installato all’interno di un’infrastruttura di server virtuali (Service Cloud presso il CED del CASPUR, prevede l’accesso in piattaforma in modalità SaaS (Software as a Service, che garantisce le piene funzionalità del servizio ad un costo notevolmente contenuto.EnLibrarians and managers of a library system have to face with relevant problems when service quality measurement in libraries is concerned. The usage of ICT based solutions for measurement campaign, data assessment and analysis, seems to be an efficient way to cope with those issues. In the past few years a software company from Cagliari (XSystems has introduced a complete, web based software solution for quality measurement in a library or a library system, called SimonLib™, that can easily address the typical technical and logistic obstacles of complex service quality measurement process. In order to offer a reliable service based on SimonLib software for

  20. Growth of Amorphous and Epitaxial ZnSiP2-Si Alloys on Si

    Energy Technology Data Exchange (ETDEWEB)

    Tamboli, Adele C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinez, Aaron [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Link, Elisa M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Norman, Andrew [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Schnepf, Rekha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Perkins, Craig [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Stradins, Paul [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Toberer, Eric [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Leick, Noemi [Formerly NREL

    2018-01-03

    ZnSiP2 is a wide band gap material that is lattice matched with Si, offering the potential for Si-based optoelectronic materials and devices, including multijunction photovoltaics. We present a carbon-free chemical vapor deposition process for the growth of both epitaxial and amorphous thin films of ZnSiP2-Si alloys with tunable Si content on Si substrates. Si alloy content is widely tunable across the full composition space in amorphous films. Optical absorption of these films reveals relatively little variation with Si content, despite the fact that ZnSiP2 has a much wider band gap of 2.1 eV. Post-growth crystallization of Si-rich films resulted in epitaxial alignment, as measured by X-ray diffraction and transmission electron microscopy. These films have an optical absorption onset near 1.1 eV, suggesting the possibility of band gap tuning with Si content in crystalline films. The optical absorption is comparably strong to pure ZnSiP2, suggesting a more direct transition than in pure Si.

  1. A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d’Arc Cave (Ardèche, France)?

    Science.gov (United States)

    Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean–François; Geneste, Jean-Michel

    2016-01-01

    Among the paintings and engravings found in the Chauvet-Pont d’Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d’Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey. PMID:26745626

  2. A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d'Arc Cave (Ardèche, France)?

    Science.gov (United States)

    Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean-François; Geneste, Jean-Michel

    2016-01-01

    Among the paintings and engravings found in the Chauvet-Pont d'Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d'Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey.

  3. Si-to-Si wafer bonding using evaporated glass

    DEFF Research Database (Denmark)

    Reus, Roger De; Lindahl, M.

    1997-01-01

    Anodic bonding of Si to Si four inch wafers using evaporated glass was performed in air at temperatures ranging from 300°C to 450°C. Although annealing of Si/glass structures around 340°C for 15 minutes eliminates stress, the bonded wafer pairs exhibit compressive stress. Pull testing revealed...

  4. Admittance of a-Si:H/c-Si Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Gall, S.; Hirschauer, R.; Braeunig, D. [Hahn-Meitner-Inst., Berlin (Germany). Dept. AT; Kolter, M. [Forschungszentrum Juelich (Germany)

    1996-12-31

    Heterojunction devices, based on hydrogenated amorphous silicon (a-Si:H) and single crystalline silicon (c-Si), are likely candidates for high efficiency solar cells. The authors have measured the admittance (conductance and capacitance) of a-Si:H/c-Si heterostructure Schottky diodes as a function of frequency, temperature and voltage in the dark and under spectral illumination (in the wavelength range between {lambda} = 500nm and {lambda} = 1,200nm). Thus, it is possible to observe the activation/deactivation of trapping-detrapping effects within the a-Si:H layer (near the a-SiH/c-Si interface). They have determined the conduction band offset of the a-Si:H/c-Si heterostructure. The spectral behavior of the admittance is dominated by the absorption of light in the c-Si and the valence band offset of the heterojunction. The authors have also developed an equivalent circuit of the a-Si:H/c-Si heterostructure Schottky diode in the dark, which is capable of describing the measured behavior.

  5. Helimagnetic order in bulk MnSi and CoSi/MnSi superlattices

    Science.gov (United States)

    Loh, G. C.; Khoo, K. H.; Gan, C. K.

    2017-01-01

    Skyrmions are nanoscopic whirls of spins that reside in chiral magnets. It is only fairly recent that a plethora of applications for these quasiparticles emerges, especially in data storage. On the other hand, spin spirals are the periodic analogs of skyrmions, and are equally imperative in the course of exploration to enhance our understanding of helimagnetism. In this study, a new infrastructure based on the B20 compound, MnSi is propounded as a hosting material for spin spirals; alternating thin layers of CoSi and MnSi in the superlattice form provides a facile way of varying the properties of the spin spirals across a continuum. Using first-principles calculations based on full-potential linearized augmented plane-wave (FLAPW)-based density functional theory (DFT), the spin order of bulk MnSi, MnSi film, and the CoSi/MnSi superlattice is investigated. Spin dispersion plots as a function of propagation vectors show that the spiral size changes in the presence of CoSi - we find that the size of the spiral is reduced in the superlattice with thin CoSi layers (CoSi:MnSi=1:1 thickness ratio), whilst at a larger CoSi:MnSi=2:1 thickness ratio, the material behaves as a ferromagnet. In a similar fashion, the spin moment and orbital occupancy depend significantly on the thickness of the CoSi layers. However, the exchange interaction between Mn atoms appears to be generally impervious to the presence of CoSi. Succinctly, the CoSi/MnSi superlattice could be an excellent functional material in data storage applications.

  6. Reliability implications of defects in high temperature annealed Si/SiO{sub 2}/Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Warren, W.L.; Fleetwood, D.M.; Shaneyfelt, M.R.; Winokur, P.S. [Sandia National Labs., Albuquerque, NM (United States); Devine, R.A.B.; Mathiot, D. [France Telecom/CNET, Meylan (France); Wilson, I.H.; Xu, J.B. [Chinese Univ. of Hong Kong (Hong Kong)

    1994-08-01

    High-temperature post-oxidation annealing of poly-Si/SiO{sub 2}/Si structures such as metal-oxide-semiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. The authors have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO{sub 2} interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases, the origin of the defects may be attributed to out-diffusion of O from the SiO{sub 2} network into the Si substrate with associated reduction of the oxide. The authors present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO{sub 2} and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO{sub 2}/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.

  7. Strained Si/SiGe MOS transistor model

    Directory of Open Access Journals (Sweden)

    Tatjana Pešić-Brđanin

    2009-06-01

    Full Text Available In this paper we describe a new model of surfacechannel strained-Si/SiGe MOSFET based on the extension of non-quasi-static (NQS circuit model previously derived for bulk-Si devices. Basic equations of the NQS model have been modified to account for the new physical parameters of strained-Si and relaxed-SiGe layers. From the comparisons with measurements, it is shown that a modified NQS MOS including steady-state self heating can accurately predict DC characteristics of Strained Silicon MOSFETs.

  8. Brazing SiC/SiC Composites to Metals

    Science.gov (United States)

    Steffier, Wayne S.

    2004-01-01

    Experiments have shown that active brazing alloys (ABAs) can be used to join SiC/SiC composite materials to metals, with bond strengths sufficient for some structural applications. The SiC/SiC composite coupons used in the experiments were made from polymerbased SiC fiber preforms that were chemical-vapor-infiltrated with SiC to form SiC matrices. Some of the metal coupons used in the experiments were made from 304 stainless steel; others were made from oxygen-free, high-conductivity copper. Three ABAs were chosen for the experiments: two were chosen randomly from among a number of ABAs that were on hand at the time; the third ABA was chosen because its titanium content (1.25 percent) is less than those of the other two ABAs (1.75 and 4.5 percent, respectively) and it was desired to evaluate the effect of reducing the titanium content, as described below. The characteristics of ABAs that are considered to be beneficial for the purpose of joining SiC/SiC to metal include wettability, reactivity, and adhesion to SiC-based ceramics. Prior to further development, it was verified that the three chosen ABAs have these characteristics. For each ABA, suitable vacuum brazing process conditions were established empirically by producing a series of (SiC/SiC)/ABA wetting samples. These samples were then sectioned and subjected to scanning electron microscopy (SEM) and energy-dispersive x-ray spectrometry (EDS) for analysis of their microstructures and compositions. Specimens for destructive mechanical tests were fabricated by brazing of lap joints between SiC/SiC coupons 1/8-in. (.3.2- mm) thick and, variously, stainless steel or copper tabs. The results of destructive mechanical tests and the SEM/EDS analysis were used to guide the development of a viable method of brazing the affected materials.

  9. Highly sensitive NIR PtSi/Si-nanostructure detectors

    Science.gov (United States)

    Li, Hua-gao; Guo, Pei; Yuan, An-bo; Long, Fei; Li, Rui-zhi; Li, Ping; Li, Yi

    2016-10-01

    We report a high external quantum efficiency (EQE) photodiode detector with PtSi/Si-nanostructures. Black silicon nanostructures were fabricated by metal-assist chemical etching (MCE), a 2 nm Pt layer was subsequently deposited on black silicon surface by DC magnetron sputtering system, and PtSi/Si-nanostructures were formed in vacuum annealing at 450 oC for 5 min. As the PtSi/Si-nanostructures presented a spiky shape, the absorption of incident light was remarkably enhanced for the repeat reflection and absorption. The breakdown voltage, dark current, threshold voltage and responsivity of the device were investigated to evaluate the performance of the PtSi/Si-nanostructures detector. The threshold voltage and dark currents of the PtSi/Si-nanostructure photodiode tends to be slightly higher than those of the standard diodes. The breakdown voltage remarkably was reduced because of existing avalanche breakdown in PtSi/Si-nanostructures. However, the photodiodes had high response at room temperature in near infrared region. At -5 V reverse bias voltage, the responsivity was 0.72 A/W in 1064 nm wavelength, and the EQE was 83.9%. By increasing the reverse bias voltage, the responsivity increased. At -60 V reverse bias voltage, the responsivity was 3.5 A/W, and the EQE was 407.5%, which means the quantum efficiency of PtSi/Si-nanostructure photodiodes was about 10 times higher than that of a standard diode. Future research includes how to apply this technology to enhance the NIR sensitivity of image sensors, such as Charge Coupled Devices (CCD).

  10. Deformation effects in the 28 Si+ 12 C and 28 Si+ 28 Si reactions

    Indian Academy of Sciences (India)

    Deformation effects in the 28Si + 12C and 28Si + 28Si reactions. C Bhattacharya M Rousseau C Beck V Rauch R M Freeman R Nouicer F Haas O Dorvaux K Eddahbi P Papka O Stezwski S Szilner D Mahboub A Szanto De Toledo A Hachem E Martin S J Sanders. Contributed Papers : Nuclear reactions Volume 57 Issue 1 ...

  11. «Possino tante belle curiosità vedersi, prima che in Torino, in Firenze»: relazioni tra Medici e Savoia nel secondo Seicento attraverso Donato Rossetti / «Possino tante belle curiosità vedersi, prima che in Torino, in Firenze» (Could such a lot of beautiful curiosities be seen in Turin earlier than in Florence : relationships between the Medici and the Savoia during the second half of the 17th Century through Donato Rossetti

    Directory of Open Access Journals (Sweden)

    Roberta Piccinelli

    2014-06-01

    Full Text Available Il saggio presenta alcuni risultati dell’indagine archivistica condotta sulle filze Savoia del fondo Mediceo del Principato dell’Archivio di Stato di Firenze. I documenti, letti criticamente e selezionati attraverso una prospettiva storico artistica, permettono di mettere in luce nuovi aspetti della figura dell’ingegnere livornese Donato Rossetti, il quale svolge il ruolo di intermediario informativo artistico tra Torino e Firenze. Attraverso suoi dispacci da Torino e missive inviate da Francesco Bondicchi da Milano a Firenze emergono sia alcuni aspetti inediti delle relazioni tra le due corti, sia il rapporto biunivoco tra centri e periferie che si precisa nel corso del Seicento. A metà secolo il ruolo di modello svolto da Firenze fa sentire ancora la propria influenza al di fuori dei confini del granducato e contemporaneamente Firenze guarda con vivo interesse alla scena artistica e urbanistica torinese. Relations between the Savoia and the Florentine court were very intense during the early modern age. Almost every day, diplomatics and residents in the Savoia court sent letters and avvisi to Florence by revealing interesting details on the everyday life and by shedding light on a range of relevant political, diplomatic, familiar and artistic dynamics. Florentine ambassadors’ or intermediaries’ reports - such as Donato Rossetti’s letters - focus on the first concern of the Savoia court, after settling in Turin, that was to build a fortified citadel and to redraw the plan of the city. During my systematic analysis of Florentine court documents at the Florence State Archive, I uncovered compelling evidence of these intricate affairs regarding the rebuilding of Turin, and these unpublished documents shed new light both on the expansion of the city and on relations between Savoia and Medici courts. This paper provide evidence to suggest that Florence was considered by the Savoy Court as the leading innovator in visual arts and

  12. Günter Eich : Nicht geführte Gespräche (1964). Ein Gedicht des Schweigens im Dialog (mit sich selbst)1

    OpenAIRE

    Haberkamm, Klaus

    2012-01-01

    Le poème Nicht geführte Gespräche, qui relève de la littérature hermétique, s’inscrit dans la tension paradoxale entre le chiffre, ce qui se ferme à la réception, et l’élan qui pousse de diverses manières à la communication. Comme le montre l’analyse détaillée du texte, le poème est engagé dans un dialogue, entre autres avec lui-même, au sens où il thématise et figure le silence dans l'acte de parole. Il est en dialogue avec son auteur et les théories qu’il représente, au sens où, considéré s...

  13. Evita Perón y el Che Guevara: De la historia a la construcción literaria del mito biográfico

    Directory of Open Access Journals (Sweden)

    Cecilia López Badano

    2014-06-01

    Full Text Available Eva Perón y el Che Guevara son dos de las figuras paradigmáticas argentinas, conocidas internacionalmente a través no sólo de sus vidas, que pueden reconstruirse a partir de documentos históricos, sino por el mito nacional - e internacional - que la muerte temprana ha configurado con ambos mediante la ayuda de la literatura y el cine, expandiendo ficcionalmente el matiz revolucionario de su accionar. El presente texto se propone, en consecuencia, dar cuenta de esas "capas" ficcionales que conforman la construcción estética de los dos mitos biográficos e inciden en la evaluación de sus protagonistas reales, modelando la percepción de ambos, particularmente, la considerada por el gran público más que por los especialistas.

  14. Relevé 3D de gravures fines paléolithiques dans l’abri du Colombier (gorges de l’Ardèche

    Directory of Open Access Journals (Sweden)

    Marc Azéma

    2012-04-01

    Full Text Available Figure 1Le bouquetin à pattes multiples (« en marche » de l’abri du Colombier (ArdèchePhot. Norbert Aujoulat. © Ministère de la Culture, DAPA, CNP, avec l’autorisation du propriétaire, M. Henry HellyL’exposition temporaire « Préhistoire de la bande dessinée et du dessin animé » consacrée à la vulgarisation d’une partie des travaux de Marc Azéma sur la représentation du mouvement dans l’art préhistorique a été l’occasion de réaliser une opération de relevé 3D (scan laser sur un abri gravé m...

  15. Deux comparatismes pour une anthropologie historique

    Directory of Open Access Journals (Sweden)

    Pierre-Olivier Dittmar

    2010-06-01

    Full Text Available Malgré des appels répétés depuis plus d’un siècle de la part des historiens, le comparatisme, qui est un élément majeur de l’anthropologie, demeure très peu pratiqué. Ce rejet est ici analysé comme un refus d’une quête des invariants de l’homme qui aboutirait à des résultats an-historiques. Un autre comparatisme est cependant possible, qui instrumentalise la confrontation des univers pour mieux relever les différences. C’est les conditions et les avantages d’une telle pratique qui sont ici exposés, à partir de l’exemple des tabous alimentaires.Despite the repeated calls by some historians for more than a century, many seldom practice a major element of anthropology: comparativism. This paper will analyze this rejection as a refusal to investigate the constants of the human experience that lead to a-historical conclusions. However, another kind of comparativism is possible, one that examines the contrast between cultures in order to better understand their differences. Using the case of dietary taboos, this paper will look at the conditions and advantages of such a practice.Nonostante i molteplici appelli da più di un secolo da parte degli storici, il comparatismo, che costituisce un elemento fondamentale dell’antropologia, è ancora oggi troppo poco spesso praticato. Si proporrà di interpretare questo rifiuto come un rifiuto della ricerca di invarianti umane che condurrebbe a risultati a-storici. Un’altra forma di comparatismo è nondimeno possibile, una forma precisamente che ricorre al confronto di universi diversi per meglio comprenderne le difference reciproche. L’articolo espone le condizioni e i vantaggi di questa metodologia di ricerca, a partire dall’esempio degli interdetti alimentari.

  16. Creep Investigation of SiCf-SiBC Composites

    Science.gov (United States)

    Farizy, Gaëlle; Chermant, Jean-Louis; Vicens, Jean; Sangleboeuf, Jean-Christophe

    The concept of ceramic matrix composites was proposed in the eighties to be used in the aeronautical and space domains. Classical SiCf-SiC have changed into complex materials, such as SiCf-SiBC investigated in this work: that composite is reinforced with SiC Hi-Nicalon fibers and has a multi-layer and self-sealing matrix. This matrix has been fabricated by means of several chemical vapor infiltrations with different compositions. Prior to the matrix infiltration, a pyrocarbon interphase has been deposited on the fibrous preform. The self-sealing property of this composite is due to the presence of boron in certain matrix layers, which will react with the atmosphere and particularly oxygen, to create a sealant glass, which protects pyrocarbon and SiC fibers.

  17. Synthesis and characterization of laminated Si/SiC composites

    Directory of Open Access Journals (Sweden)

    Salma M. Naga

    2013-01-01

    Full Text Available Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results.

  18. Structure of MnSi on SiC(0001)

    Science.gov (United States)

    Meynell, S. A.; Spitzig, A.; Edwards, B.; Robertson, M. D.; Kalliecharan, D.; Kreplak, L.; Monchesky, T. L.

    2016-11-01

    We report on the growth and magnetoresistance of MnSi films grown on SiC(0001) by molecular beam epitaxy. The growth resulted in a textured MnSi(111) film with a predominantly [1 1 ¯0 ] MnSi (111 )∥[11 2 ¯0 ] SiC(0001) epitaxial relationship, as demonstrated by transmission electron microscopy, reflection high energy electron diffraction, and atomic force microscopy. The 500 ∘C temperature required to crystallize the film leads to a dewetting of the MnSi layer. Although the sign of the lattice mismatch suggested the films would be under compressive stress, the films acquire an in-plane tensile strain likely driven by the difference in thermal expansion coefficients between the film and substrate during annealing. As a result, the magnetoresistive response demonstrates that the films possess a hard-axis out-of-plane magnetocrystalline anisotropy.

  19. Identification of the Mg2+-binding site in the P-type ATPase and phosphatase members of the HAD (haloacid dehalogenase) superfamily by structural similarity to the response regulator protein CheY

    NARCIS (Netherlands)

    Ridder, Ivo S.; Dijkstra, Bauke W.

    1999-01-01

    The large HAD (haloacid dehalogenase) superfamily of hydrolases comprises P-type ATPases, phosphatases, epoxide hydrolases and L-2-haloacid dehalogenases. A comparison of the three-dimensional structure of L-2-haloacid dehalogenase with that of the response regulator protein CheY allowed the

  20. Decision making information systems and data base management; Applicazioni dei sistemi di supporto alle decisioni manageriali in un ente fortemente decentrato. Sviluppo di un prototipo per la valutazione di nuovi progetti

    Energy Technology Data Exchange (ETDEWEB)

    Minelle, F. [Rome, Univ. `La Sapienza` (Italy). Fac. di Scienze Matematiche, Fisiche e Naturali; Di Marco, R.A. [ENEA, Rome (Italy). Funzione Centrale Informatica; Belli, A.

    1997-01-01

    con essi; e di rpesentare un prototipo di tali sistemi. Da una fase preliminare di analisi dell`Ente e dei suoi Sistemi Informativi, volta a capire quali problematiche potessero essere piu` efficacemente supportate con sistemi di questo tipo, si afronta una di esse: la valutazione di nuovi progetti, individuando i parametri, o le grandezze chiave, che influenzano e determinano la decisione. Si descrivono, poi, i modelli, ricavati da questi ultimi, che permettono all`utente, tramite una semplice rappresentazione dei risultati, di valutare i vantaggi e gli svantaggi di un nuovo progetto. Dai modelli, dall`analisi dei dati ad essi necessari e dai requisiti di semplicita` e facilita` d`uso dell`interfaccia utente, si e` realizzato un prototipo. A questo scopo si e` seguito il modelllo di Sprague e Carlson che prevede una Base di Dati, una Base di Modelli e un Sistema Software.

  1. SiC/SiC Cladding Materials Properties Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Snead, Mary A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Singh, Gyanender P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    When a new class of material is considered for a nuclear core structure, the in-pile performance is usually assessed based on multi-physics modeling in coordination with experiments. This report aims to provide data for the mechanical and physical properties and environmental resistance of silicon carbide (SiC) fiber–reinforced SiC matrix (SiC/SiC) composites for use in modeling for their application as accidenttolerant fuel cladding for light water reactors (LWRs). The properties are specific for tube geometry, although many properties can be predicted from planar specimen data. This report presents various properties, including mechanical properties, thermal properties, chemical stability under normal and offnormal operation conditions, hermeticity, and irradiation resistance. Table S.1 summarizes those properties mainly for nuclear-grade SiC/SiC composites fabricated via chemical vapor infiltration (CVI). While most of the important properties are available, this work found that data for the in-pile hydrothermal corrosion resistance of SiC materials and for thermal properties of tube materials are lacking for evaluation of SiC-based cladding for LWR applications.

  2. Joining of SiC ceramics and SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1995-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method has the potential to facilitate the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent efforts have focused on transferring the joining technology to industry. Several industrial partners have been identified and collaborative research projects are in progress. Investigations are focusing on applying the joining method to sintered a-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  3. Joining of SiC ceramics and SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1996-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method will permit the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent emphasis has been given to technology transfer activities, and several collaborative research efforts are in progress. Investigations are focusing on applying the joining method to sintered {alpha}-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  4. Methods of radiation effects evaluation of SiC/SiC composite and SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. Several methods for radiation effects evaluation of SiC fibers and fiber-reinforced SiC/SiC composite are presented.

  5. L'eta d'oro:campagna di promozione dell' attivitá fisica per adulti di media etá (dai 50 ai 65 anni

    Directory of Open Access Journals (Sweden)

    F. Francia

    2003-05-01

    Full Text Available

    La metanalisi degli studi scientifici ha dimostrato che l’attività fisica, svolta regolarmente e di sufficiente entità, contribuisce a ridurre i rischi di morte per tutte le cause ed ha effetti benefici su molte malattie degenerative e metaboliche collegate all’ aumento della sedentarietà. L’attività motoria come elemento di prevenzione diventa, pertanto, uno degli obiettivi individuati dai programmi di educazione alla salute europei riproposto in Italia coi Piani Sanitari 1998 - 2000 e 2001 - 2003. Gli Interventi di promozione della salute, più frequentemente indirizzati a targets giovanili ed anziani, rischiano di trascurare una fascia di età, quella dei 50 - 65, che può essere particolarmente critica per una serie di fisiologici cambiamenti psico fisici che possono enfatizzare la tendenza alla sedentarietà, già favorita da attività lavorative e sociali fisicamente poco impegnative.

    Con il concorso di specialisti nelle diverse discipline è stato predisposta una campagna informativa tesa ad evidenziare i vantaggi di uno stile di vita fisicamente attivo che parte dall’espletamento delle attività quotidiane e si completa con un’attività motoria da svolgere con regolarità durante l’arco della settimana. In particolare si sono suggeriti pacchetti di attività strutturati in modo da andare incontro alle diverse esigenze e preferenze e motivare anche i soggetti più sedentari.

    Il programma di allenamento proposto prevede attività per lo sviluppo ed il mantenimento di estensibilità, forza muscolare e capacità aerobica.

    Per la promozione e la diffusione della campagna si sono strette una serie di alleanze con i medici di medicina generale, centri specializzati in medicina dello sport, assessorati comunali allo sport, alla sanità, al traffico, quartieri, federazioni sportive ed enti di promozione. Accanto a momenti specificamente dedicati (con presenza di specialisti e trainer, la promozione sar

  6. Tassi di cambio fluttuanti, deprezzamento valutario e domanda effettiva (Floating exchange rates, currency depreciation and actual demand

    Directory of Open Access Journals (Sweden)

    Julio López

    2012-04-01

    Full Text Available Il presente articolo esamina i vantaggi relativi dei tassi di cambio fluttuanti nei confronti di un regime di tassi di cambio a parità rigidamente ancorate (hard peg, ponendo particolare enfasi sulle implicazioni per la domanda effettiva. In particolare, esso valuta se un deprezzamento della valuta abbia un effetto benefico sulla domanda aggregata e dunque sull’occupazione. Si sostiene che tale questione è centrale per il principio della domanda effettiva, e che l’idea che un deprezzamento valutario sia in grado di stabilizzare la domanda effettiva, equivale in larga misura a sostenere che la flessibilità (verso il basso dei salari nominali (e reali possa assicurare la piena occupazione. Coerentemente con ciò, viene analizzata la relazione tra la flessibilità verso il basso dei salari e la domanda effettiva, e viene valutata criticamente (dal punto di vista sia teorico sia empirico l’ipotesi che la flessibilità del tasso di cambio possa avere proprietà stabilizzanti quando si tenga conto di shock esogeni di varia natura. L’articolo si chiude con brevi deduzioni di teoria e di politica economiche.   This paper examines the relative advantages of floating exchange rates against a system of exchange rates for the same rigidly anchored (hard peg, with particular emphasis on the implications for effective demand. In particular, it will assess whether a currency depreciation has a beneficial effect on aggregate demand and hence employment. It is argued that this issue is central to the principle of effective demand, and that the idea that a currency depreciation is able to stabilize the effective demand, is equivalent to a large extent to support that flexibility (down in nominal wages (and real to ensure full employment. Consistent with this, we analyze the relationship between the downward flexibility of wages and effective demand, and is critically evaluated (in terms of both theoretical and empirical hypothesis that the flexibility

  7. Geochemical characteristics of fault core and damage zones of the Hong-Che Fault Zone of the Junggar Basin (NW China) with implications for the fault sealing process

    Science.gov (United States)

    Liu, Yin; Wu, Kongyou; Wang, Xi; Pei, Yangwen; Liu, Bo; Guo, Jianxun

    2017-08-01

    Faults may have a complex internal structure, including fault core and damage zone, and can act as major conduits for fluid migration. The migration of fluids along faults is generally associated with strong fluid-rock interaction, forming large amounts of cement that fill in the fractures. The cementation of the fault fractures is considered to be one of the important parameters of fault sealing. The different components of faults have diverse geochemical features because of varying physical characteristics. The investigation of the geochemical characteristics of the fault and damage zones could provide important information about the fault sealing process, which is very important in oil and gas exploration. To understand the fault-cemented sealing process, detailed geochemical studies were conducted on the fault and damage zones of the Hong-Che Fault of the northwestern Junggar Basin in China. The major and trace element data of our study suggest that the fault core is characterized by higher loss on ignition (LOI), potassium loss, Chemical Index of Alteration (CIA), and Plagioclase Index of Alteration (PIA) values and lower high field strength element (HFSE), large-ion lithosphile element (LILE), and rare earth element (REE) concentrations compared with the damage zone, implying more serious elemental loss and weathering of the fault core compared with the damage zone during faulting. The carbon and oxygen isotope data reveal that the cement of the Hong-Che Fault Zone formed due to multiple sources of fluids. The fault core was mainly affected by deep sources of hydrothermal fluids. In combination with previous studies, we suggest a potential fault-cemented sealing process during the period of fault movement. The fault core acts as the fluid conduit during faulting. After faulting, the fault core is cemented and the damage zone becomes the major conduit for fluid migration. The cementation firstly occurs on two sides of the damage zone in the upper part of the

  8. Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA

    Science.gov (United States)

    Bishop, Janice L.; Franz, Heather B.; Goetz, Walter; Blake, David F.; Freissinet, Caroline; Steininger, Harald; Goesmann, Fred; Brinckerhoff, William B.; Getty, Stephanie; Pinnick, Veronica T.; Mahaffy, Paul R.; Dyar, M. Darby

    2013-06-01

    Coordinated analyses of mineralogy and chemistry of sediments from the Antarctic Dry Valleys illustrate how data obtained using flight-ready technology of current NASA and ESA missions can be combined for greater understanding of the samples. Mineralogy was measured by X-ray diffraction (XRD) and visible/near-infrared (VNIR) reflectance spectroscopy. Chemical analyses utilized a quadrupole mass spectrometer (QMS) to perform pyrolysis-evolved gas analysis (EGA) and gas chromatography-mass spectrometry (GC/MS) both with and without derivatization, as well as laser desorption-mass spectrometry (LD/MS) techniques. These analyses are designed to demonstrate some of the capabilities of near-term landed Mars missions, to provide ground truthing of VNIR reflectance data acquired from orbit by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on MRO and to provide detection limits for surface-operated instruments: the Chemistry and Mineralogy (CheMin) and Sample Analysis at Mars (SAM) instrument suites onboard Mars Science Laboratory (MSL) and the Mars Organic Molecule Analyzer (MOMA) onboard ExoMars-2018. The new data from this study are compared with previous analyses of the sediments performed with other techniques. Tremolite was found in the oxic region samples for the first time using the CheMin-like XRD instrument. The NIR spectral features of tremolite are consistent with those observed in these samples. Although the tremolite bands are weak in spectra of these samples, spectral features near 2.32 and 2.39 μm could be detected by CRISM if tremolite is present on the martian surface. Allophane was found to be a good match to weak NIR features at ˜1.37-1.41, 1.92, and 2.19 μm in spectra of the oxic region sediments and is a common component of immature volcanic soils. Biogenic methane was found to be associated with calcite in the oxic region samples by the SAM/EGA instrument and a phosphoric acid derivative was found in the anoxic region sample using

  9. The CheMin XRD on the Mars Science Laboratory Rover Curiosity: Construction, Operation, and Quantitative Mineralogical Results from the Surface of Mars

    Science.gov (United States)

    Blake, David F.

    2015-01-01

    The Mars Science Laboratory mission was launched from Cape Canaveral, Florida on Nov. 26, 2011 and landed in Gale crater, Mars on Aug. 6, 2012. MSL's mission is to identify and characterize ancient "habitable" environments on Mars. MSL's precision landing system placed the Curiosity rover within 2 km of the center of its 20 X 6 km landing ellipse, next to Gale's central mound, a 5,000 meter high pile of laminated sediment which may contain 1 billion years of Mars history. Curiosity carries with it a full suite of analytical instruments, including the CheMin X-ray diffractometer, the first XRD flown in space. CheMin is essentially a transmission X-ray pinhole camera. A fine-focus Co source and collimator transmits a 50µm beam through a powdered sample held between X-ray transparent plastic windows. The sample holder is shaken by a piezoelectric actuator such that the powder flows like a liquid, each grain passing in random orientation through the beam over time. Forward-diffracted and fluoresced X-ray photons from the sample are detected by an X-ray sensitive Charge Coupled Device (CCD) operated in single photon counting mode. When operated in this way, both the x,y position and the energy of each photon are detected. The resulting energy-selected Co Kalpha Debye-Scherrer pattern is used to determine the identities and amounts of minerals present via Rietveld refinement, and a histogram of all X-ray events constitutes an X-ray fluorescence analysis of the sample.The key role that definitive mineralogy plays in understanding the Martian surface is a consequence of the fact that minerals are thermodynamic phases, having known and specific ranges of temperature, pressure and composition within which they are stable. More than simple compositional analysis, definitive mineralogical analysis can provide information about pressure/temperature conditions of formation, past climate, water activity and the like. Definitive mineralogical analyses are necessary to establish

  10. Rock shelter occupation during isotopic stage 5: level D of the site of Payre (Ardèche, France. Territorial organisation and intra-site activities

    Directory of Open Access Journals (Sweden)

    Moncel, Marie-Hélène

    2007-06-01

    Full Text Available This paper presents the results obtained from an interdisciplinary study of the level D archaeological assemblages from Payre (Ardèche, France. This site is dated to the final of OIS 6 and the beginning of OIS 5. The combined analysis of the lithic and faunal assemblages accumulated and their management “into” and “out of” the site gives a better understanding of the behaviour of the Neanderthal groups that inhabited it. This study has allowed us to correlate the territorial exploitation for game hunting and for raw material procurement, within the context of seasonal short term occupations probably during the end of autumn and the beginning of winter.  

    Este artículo presenta los resultados obtenidos a través del estudio multidisciplinar del registro arqueológico del nivel D del yacimiento de Payre (Ardèche, Francia datado entre el final del OIS 6 y el comienzo del OIS 5. El análisis conjunto de la industria lítica y de los restos óseos recuperados en el yacimiento y de la gestión de dichos recursos dentro y fuera de él, ha hecho posible la comprensión de los comportamientos humanos de los grupos neandertales que lo ocuparon. Dicho estudio nos ha permitido poner en relación el tipo de explotación del territorio de caza y de captación de materias primas, dentro del marco de ocupaciones estacionales de corta duración desarrolladas probablemente entre el final del otoño y el principio del invierno.  

  11. Synthesis and structural property of Si nanosheets connected to Si nanowires using MnCl{sub 2}/Si powder source

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Erchao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Ueki, Akiko [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Meng, Xiang [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Suzuki, Hiroaki [Graduate School of Engineering, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Itahara, Hiroshi [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Tatsuoka, Hirokazu, E-mail: tatsuoka.hirokazu@shizuoka.ac.jp [Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan)

    2016-08-15

    Graphical abstract: Si nanosheets connected to Si nanowires synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst avoid the use of air-sensitive SiH{sub 4} or SiCl{sub 4}. It was evident from these structural features of the nanosheets (leaf blade) with nanowires (petiole) that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes of the Si(111) nanosheets was clearly explained by the interference with the extra diffraction spots that arose due to the reciprocal lattice streaking effect. - Highlights: • New Si nanosheets connected to Si nanowires were synthesized using MnCl{sub 2}/Si powders. • The synthesis method has benefits in terms of avoiding air sensitive SiH{sub 4} or SiCl{sub 4}. • Structural property and electron diffraction of the Si nanosheets were clarified. • Odd lattice fringes of the Si nanosheets observed by HRTEM were clearly explained. - Abstract: Si nanosheets connected to Si nanowires were synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH{sub 4} or SiCl{sub 4}. The existence of the Si nanosheets connected to the Si<111> nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of <211> perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.

  12. Si nanoparticle interfaces in Si/SiO solar cell materials

    DEFF Research Database (Denmark)

    Kilpeläinen, S.; Kujala, J.; Tuomisto, F.

    2013-01-01

    Novel solar cell materials consisting of Si nanoparticles embedded in SiO2 layers have been studied using positron annihilation spectroscopy in Doppler broadening mode and photoluminescence. Two positron-trapping interface states are observed after high temperature annealing at 1100 °C. One...

  13. a-Si:H/SiNW shell/core for SiNW solar cell applications

    Science.gov (United States)

    2013-01-01

    Vertically aligned silicon nanowires have been synthesized by the chemical etching of silicon wafers. The influence of a hydrogenated amorphous silicon (a-Si:H) layer (shell) on top of a silicon nanowire (SiNW) solar cell has been investigated. The optical properties of a-Si:H/SiNWs and SiNWs are examined in terms of optical reflection and absorption properties. In the presence of the a-Si:H shell, 5.2% reflection ratio in the spectral range (250 to 1,000 nm) is achieved with a superior absorption property with an average over 87% of the incident light. In addition, the characteristics of the solar cell have been significantly improved, which exhibits higher open-circuit voltage, short-circuit current, and efficiency by more than 15%, 12%, and 37%, respectively, compared with planar SiNW solar cells. Based on the current–voltage measurements and morphology results, we show that the a-Si:H shell can passivate the defects generated by wet etching processes. PMID:24195734

  14. Defecography of rectal wall prolapse conditions; Defecografia nelle malattie parietali del retto da prolasso

    Energy Technology Data Exchange (ETDEWEB)

    Salzano, A.; Muto, M.; De Rosa, A. [Azienda Sanitaria di Rilievo Nazionale A. Cardarelli, Naples (Italy). Servizio di Neuroradiologia; Ginolfi, F.; Carbone, M.; Amodio, F.; Rossi, E. [Naples Univ. Federico 2. (Italy). Ist. di Scienze Radiologiche; Tuccillo, M. [Azienda Sanitaria di Rilirvo Nazionale A. Cardarelli, Naples (Italy). 2. Servizio di Radiologia

    1999-06-01

    Pelvic floor and rectal prolapse conditions have greatly benefited by new imaging and instrumental diagnostic approaches, and especially defecography, for both pathophysiological interpretation and differential diagnosis. The authors investigated the efficacy of defecography in the assessment of rectal prolapse, and in particular the role of videproctography in diagnosis such dynamic disorders. The dynamic changes of ampulla are well depicted by videoproctography, which showed anorectum normalization and spontaneous reduction of invagination after intussusception. Defecography exhibited good capabilities in showing rectal wall function abnormalities. Finally, some features of videoproctography such as low radiation dose, non-invasiveness and ease of execution, make the examination acceptable to patients with anorectal disorders and for the follow-up of rectal prolapse. [Italian] Le malattie del pavimento pelvico e dei prolassi del retto hanno tratto numerosi vantaggi da nuovi approcci di diagnostica per immagini e strumentali, specialmente dall'esame defecografico, sia nell'interpretazione fisiopatologica che nella diagnostica differenziale dei disordini anorettali. Scopo del lavoro: valutare l'efficacia della metodica defecografica nel riconoscimento delle malattie da prolasso del retto e in particolare il ruolo svolto dalla videoproctografia nella documentazione diagnostica e nel definire i principali elementi semeiologici riscontrabili in tali malattie in modo dinamico. Le fasi dinamiche della valutazione morfologica e posizionale dell'ampolla rettale sono ben evidenti nella viedeoproctografia, che documenta dopo l'intussuscezione la normalizzazione del complesso anorettale e la riduzione spontanea dell'invaginazione parietale. In questo studio si sottolineano le possibilita' diagnostiche della defecografia integrata da videoproctografia nel riconoscimento delle malattie parietali funzionali del retto e alcune peculiarita

  15. Low dose irradiation performance of SiC interphase SiC/SiC composites

    Science.gov (United States)

    Snead, L. L.; Osborne, M. C.; Lowden, R. A.; Strizak, J.; Shinavski, R. J.; More, K. L.; Eatherly, W. S.; Bailey, J.; Williams, A. M.

    1998-03-01

    Reduced oxygen Hi-Nicalon™ fiber reinforced composite SiC materials were densified with a chemically vapor infiltrated (CVI) silicon carbide (SiC) matrix and interphases of either `porous' SiC or multilayer SiC and irradiated to a neutron fluence of 1.1×10 25 n m -2 ( E>0.1 MeV) in the temperature range of 260 to 1060°C. The unirradiated properties of these composites are superior to previously studied ceramic grade Nicalon fiber reinforced/carbon interphase materials. Negligible reduction in the macroscopic matrix microcracking stress was observed after irradiation for the multilayer SiC interphase material and a slight reduction in matrix microcracking stress was observed for the composite with porous SiC interphase. The reduction in strength for the porous SiC interfacial material is greatest for the highest irradiation temperature. The ultimate fracture stress (in four point bending) following irradiation for the multilayer SiC and porous SiC interphase materials was reduced by 15% and 30%, respectively, which is an improvement over the 40% reduction suffered by irradiated ceramic grade Nicalon fiber materials fabricated in a similar fashion, though with a carbon interphase. The degradation of the mechanical properties of these composites is analyzed by comparison with the irradiation behavior of bare Hi-Nicalon fiber and Morton chemically vapor deposited (CVD) SiC. It is concluded that the degradation of these composites, as with the previous generation ceramic grade Nicalon fiber materials, is dominated by interfacial effects, though the overall degradation of fiber and hence composite is reduced for the newer low-oxygen fiber.

  16. LA DIAGNOSI DELLE COMPETENZE LINGUISTICHE IN UN CONTESTO MULTILINGUE: UN PROCESSO CONTINUO CHE FAVORISCE L’INSEGNAMENTO E L’APPRENDIMENTO INDIVIDUALIZZATO

    Directory of Open Access Journals (Sweden)

    Drorit Lengyel

    2011-07-01

    Full Text Available Il presente studio affronta il problema della valutazione diagnostica delle competenze linguistiche in contesti educativi multilingui, con particolare attenzione ai bisogni dei bambini e degli adolescenti immigrati. Vengono brevemente esposti gli obiettivi, le funzioni e i principi della valutazione diagnostica e della valutazione formativa considerate parte integrante di una educazione linguistica continua che prevede un insegnamento-apprendimento individualizzato. Sul piano teorico le procedure della valutazione diagnostica delle competenze linguistiche in contesti multilingui fanno riferimento all’apprendimento delle lingue inteso come attività socio-culturale.     Language diagnostics in multilingual settings with respect to continuous procedures as accompaniment of individualized learning and teaching   This study provides an introduction to language diagnostics in multilingual educational settings, with particular reference to the needs of children and adolescents from migrant backgrounds. It summarises the objectives and functions of language diagnostics and the principles that govern diagnostics including formative assessment, considered to be an integral part of continuous language education that emphasises individualised teaching and learning. From a theoretical perspective, diagnostic procedures in multilingual settings treat language learning as a socio-cultural activity.  

  17. Evaluation of the Addition liquor with high ammonia and Carbon Dioxide contentin the still 208 of the “Comandante Che Guevara” industry (ECG

    Directory of Open Access Journals (Sweden)

    María Elena Magaña-Haynes

    2015-12-01

    Full Text Available Adding fresh liquor through the 5th ring in still 208 of distilling liquor product (liquor obtained as a result of ammonium carbonate leaching of lateritic ore in the “Comandante Che Guevara” industry, were evaluated with the objective of reducing the dissolved nickel content of the effluent there from, as well as to improve the characteristics of the nickel carbonate which is delivered to the calcinations process. For the development of the survey, the same methodology used in 2001 for the test was applied. The results showed that by adding fresh liquor, it is possible to reduce the dissolved nickel content at the exit of the distillation column, so that the need for precipitation is minimized, thereby reducing the consumption of reagents and the and the cost for their acquisition. It was possible to corroborate the relationship between the content of NH3 at the discharge and the nickel dissolved therein appreciating that to achieve these results it is necessary to maintain the ammonia in the discharge between 1,0-1,8 g/L. The carbonate obtained in the column where liquor is added with high CO2 and NH3 reached high values of this last element in its composition and to the extent that increased sulphur content decreased. It was also seen an increase in the size of the coarse carbonates particles, which will influence in a decrease of energy consumption.

  18. Improved characterization of Si-SiO2 interfaces

    Science.gov (United States)

    Su, P.

    Silicon is the heart of modern semiconductor devices. The dominance of Si in semiconductor technology depends on the superior quality and properties of thermally grown SiO2 compared with the oxide that can be placed on any other semiconductor. The well established quasistatic and conductance methods used in the study of the Si-SiO2 interface are improved by using an effectively thin composite insulator, low carrier concentration substrates, and most importantly, low level illumination at a wavelength that creates electron hole pairs. The samples investigated had a thermally grown oxide prepared in dry oxygen. They were never exposed to H2 or H2O at an elevated temperature. The composite gate insulator was completed by having an e-gun deposited 250 A layer on LaF3. The resulting interface, subjected to the improved experimental method, yields a wealth of distinctive structure rather than the often reported featureless U-shaped interface-state density.

  19. Total Ionizing Dose Effects of Si Vertical Diffused MOSFET with SiO2 and Si3N4/SiO2 Gate Dielectrics

    Directory of Open Access Journals (Sweden)

    Jiongjiong Mo

    2017-01-01

    Full Text Available The total ionizing dose irradiation effects are investigated in Si vertical diffused MOSFETs (VDMOSs with different gate dielectrics including single SiO2 layer and double Si3N4/SiO2 layer. Radiation-induced holes trapping is greater for single SiO2 layer than for double Si3N4/SiO2 layer. Dielectric oxidation temperature dependent TID effects are also studied. Holes trapping induced negative threshold voltage shift is smaller for SiO2 at lower oxidation temperature. Gate bias during irradiation leads to different VTH shift for different gate dielectrics. Single SiO2 layer shows the worst negative VTH at VG=0 V, while double Si3N4/SiO2 shows negative VTH shift at VG=-5 V, positive VTH shift at VG=10 V, and negligible VTH shift at VG=0 V.

  20. Graphene-Si heterogeneous nanotechnology

    Science.gov (United States)

    Akinwande, Deji; Tao, Li

    2013-05-01

    It is widely envisioned that graphene, an atomic sheet of carbon that has generated very broad interest has the largest prospects for flexible smart systems and for integrated graphene-silicon (G-Si) heterogeneous very large-scale integrated (VLSI) nanoelectronics. In this work, we focus on the latter and elucidate the research progress that has been achieved for integration of graphene with Si-CMOS including: wafer-scale graphene growth by chemical vapor deposition on Cu/SiO2/Si substrates, wafer-scale graphene transfer that afforded the fabrication of over 10,000 devices, wafer-scalable mitigation strategies to restore graphene's device characteristics via fluoropolymer interaction, and demonstrations of graphene integrated with commercial Si- CMOS chips for hybrid nanoelectronics and sensors. Metrology at the wafer-scale has led to the development of custom Raman processing software (GRISP) now available on the nanohub portal. The metrology reveals that graphene grown on 4-in substrates have monolayer quality comparable to exfoliated flakes. At room temperature, the high-performance passivated graphene devices on SiO2/Si can afford average mobilities 3000cm2/V-s and gate modulation that exceeds an order of magnitude. The latest growth research has yielded graphene with high mobilities greater than 10,000cm2/V-s on oxidized silicon. Further progress requires track compatible graphene-Si integration via wafer bonding in order to translate graphene research from basic to applied research in commercial R and D laboratories to ultimately yield a viable nanotechnology.

  1. Determinação de constantes elásticas de estrutura sanduíche com núcleo em papel celulose e faces em não-tecido composto

    OpenAIRE

    Trombin, Marcio dos Santos

    2013-01-01

    Estruturas sanduíche possuem aplicações em diferentes áreas, tais como as indústrias: automotiva, naval, aeronáutica e moveleira. As razões da sua utilização vão desde a elevada eficiência estrutural até o baixo custo. Na indústria automotiva, elas são usadas em veículos convencionais, bem como em esportivos de alto desempenho. Uma alternativa de baixo custo são estruturas sanduíche com núcleos feitos em papel celulose e faces em materiais compostos termoplásticos. Alguns automóveis utilizam ...

  2. Origini Concettuali di Errori che si Riscontrano Nel Confrontare Numeri Decimali e Frazioni=Conceptual Sources of Difficulties Concerning the Ordering of Decimal Numbers and the Comparison of Fractions.

    Science.gov (United States)

    Bonotto, C.

    1993-01-01

    Examined fifth-grade students' survey responses to investigate incorrect rules that derive from children's efforts to interpret decimals as integers or as fractions. Regarding fractions, difficulties arise because only the whole-part approach to fractions is presented in elementary school. (Author/MDH)

  3. L’UTILIZZO DELLA REALTÀ AUMENTATA NELLA DIDATTICA DELL’ITALIANO L2

    Directory of Open Access Journals (Sweden)

    Giulia Lombardi

    2016-09-01

    Full Text Available L’articolo prende spunto dall’analisi di alcune tra le applicazioni mobile di realtà aumentata più famose e utilizzate sia quotidianamente che nella didattica delle materie scientifiche, per sfruttarne le potenzialità anche nell’insegnamento dell’italiano a stranieri. Dopo una brevissima panoramica che intende fare il punto sull’utilizzo delle tecnologie nella classe di lingue, vengono introdotti i concetti di mobile-learning e di realtà aumentata. A partire dai primi impieghi di questo strumento nella didattica delle materie scientifiche e tecniche, si arriva alle prime sperimentazioni d’avanguardia nelle classi di lingua, comunque molto rare: l’articolo ripercorre le tappe che portano all’introduzione praticamente pionieristica di questo metodo nella didattica dell’italiano come lingua seconda. Quindi si passa ad analizzarne tutti i vantaggi in termini di inclusione, usabilità, motivazione, versatilità ed innovazione. Nella seconda parte, vengono tratteggiate e catalogate in una tabella le caratteristiche tecniche e di impiego didattico di cinque applicazioni che ricorrono alla tecnologia della realtà aumentata: Aurasma, Wikitude, Google Goggles, Taggar, Zooburst. Nella terza e ultima parte, vengono proposte e descritte tre attività didattiche esemplificative, che vogliono guidare il docente all’utilizzo degli strumenti sopra descritti, dalla progettazione alla presentazione in aula. The use of augmented reality in italian L2 teaching This article was inspired by analyzing some of the most famous and frequently used augmented reality mobile applications that science teachers use to exploit their potential in teaching Italian to foreigners. After a brief overview of the use of technology in language classrooms, mobile-learning concepts and augmented reality are introduced. We trace the first uses of this tool in teaching scientific and technical matters, and then the initial avant-garde experiments in language

  4. Studi Tentang Pengaruh Doping Tinggi Terhadap Resistansi Basis Dan Bandgap Narrowing Pada Si/si1-xgex /Si Hbt

    OpenAIRE

    Achmad Fadhol

    2003-01-01

    Study About High Influence Doping to Base Resistance and Bandgap Narrowing at Si/Si1-xGex/Si HeterojunctionBipolar Transistor. Heterojunction is a link formed bedween two semiconductor materials and differend bandgapwhich has thinness under 50nm and grow the mixture of plate SiGe as bases. The link is an abrupt link or graded one.In this research learnt formulation of doping concentration influence to basis resistance and bandgap narrowing throughSi/Si1-xGex/Si Heterojunction Bipolar Transist...

  5. Growth of CNTs on Fe-Si catalyst prepared on Si and Al coated Si substrates.

    Science.gov (United States)

    Teng, F-Y; Ting, Jyh-Ming; Sharma, Sahendra P; Liao, Kun-Hou

    2008-03-05

    In this paper we report the effect of Al interlayers on the growth characteristics of carbon nanotubes (CNTs) using as-deposited and plasma etched Fe-Si catalyst films as the catalysts. Al interlayers having various thicknesses ranging from 2 to 42 nm were deposited on Si substrates prior to the deposition of Fe-Si catalysts. It was found that the Al interlayer diffuses into the Fe-Si catalyst during the plasma etching prior to the CNT growth, leading to the swelling and amorphization of the catalyst. This allows enhanced carbon diffusion in the catalyst and therefore a faster growth rate of the resulting CNTs. It was also found that use of an Al interlayer having a thickness of ∼3 ± 1 nm is most effective. Due to the effectiveness of this, the normally required catalyst etching is no longer needed for the growth of CNTs.

  6. SiC-SiC and C-SiC Honeycomb for Advanced Flight Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project builds upon the work done in Phase I with the development of a C-SiC CMC honeycomb material that was successfully tested for mechanical...

  7. Improving Thermomechanical Properties of SiC/SiC Composites

    Science.gov (United States)

    DiCarlo, James A.; Bhatt, Ramakrishna T.

    2006-01-01

    Today, a major thrust toward improving the thermomechanical properties of engine components lies in the development of fiber-reinforced silicon carbide matrix composite materials, including SiC-fiber/SiC-matrix composites. These materials are lighter in weight and capable of withstanding higher temperatures, relative to state-of-the-art metallic alloys and oxide-matrix composites for which maximum use temperatures are in the vicinity of 1,100 C. In addition, the toughness or damage tolerance of the SiC-matrix composites is significantly greater than that of unreinforced silicon-based monolithic ceramics. For successful application in advanced engine systems, the SiC-matrix composites should be able to withstand component service stresses and temperatures for the desired component lifetimes. Inasmuch as the high-temperature structural lives of ceramic materials are typically limited by creep-induced growth of flaws, a key property required of such composite materials is high resistance to creep under conditions of use. Also, the thermal conductivity of the materials should be as high as possible so as to minimize component thermal gradients and thermal stresses. A state-of-the-art SiC-matrix composite is typically fabricated in a three-step process: (1) fabrication of a component-shaped architectural preform reinforced by thermally stable high-performance fibers, (2) chemical-vapor infiltration (CVI) of a fiber-coating material such as boron nitride (BN) into the preform, and (3) infiltration of an SiC-based matrix into the remaining porosity in the preform. Generally, the matrices of the highest-performing composites are fabricated by initial use of a CVI SiC matrix component that is typically more thermally stable and denser than matrix components formed by processes other than CVI. As such, the initial SiC matrix component made by CVI provides better environmental protection to the coated fibers embedded within it. Also, the denser CVI SiC imparts to the

  8. Spectral characteristics of a-Si:H/c-Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gall, S.; Hirschauer, R.; Braeunig, D. [Hahn-Meitner-Institut Berlin, Department AT, Berlin (Germany); Kolter, M. [Forschungszentrum Juelich, Department ISI-PV, Juelich (Germany)

    1997-10-21

    We have examined the current-voltage characteristic of i-a-Si:H/n-c-Si heterojunction Schottky solar cells in the dark and under different illumination (spectrum AM1.5) intensities as well as the voltage- and temperature-dependent spectral response of these devices. The photocurrent from the crystalline silicon depends on both voltage and temperature due to their influence on the impact of the band offsets. From our measurements of the spectral response we conclude that there is a small conduction band offset {Delta}E{sub c} and a large valence band offset {Delta}E{sub v} at the i-a-Si:H/n-c-Si heterojunction. The large valence band offset inhibits the collection of photogenerated holes from the crystalline silicon under normal photovoltaic conditions. Thus, the current-voltage characteristic under illumination between V=0 V and V=V{sub oc} is caused only by the photocurrent from the a-Si:H layer

  9. Ionic S(N)i-Si Nucleophilic Substitution in N-Methylaniline-Induced Si-Si Bond Cleavages of Si2Cl6.

    Science.gov (United States)

    Zhang, Jie; Xie, Ju; Lee, Myong Euy; Zhang, Lin; Zuo, Yujing; Feng, Shengyu

    2016-03-24

    N-Methylaniline-induced Si-Si bond cleavage of Si2Cl6 has been theoretically studied. All calculations were performed by using DFT at the MPWB1K/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) levels. An ionic SN i-Si nucleophilic substitution mechanism, which is a newly found nucleophilic substitution in silicon-containing compounds, is proposed in the N-methylaniline-induced Si-Si bond cleavage in Si2Cl6. Unlike general S(N)i-Si nucleophilic substitutions that go through a pentacoordinated silicon transition state, ionic nucleophilic substitution goes through a tetracoordinated silicon transition state, in which the Si-Si bond is broken and siliconium ions are formed. Special cleavage of the Si-Si bond is presumably due to the good bonding strength between Si and N atoms, which leads to polarization of the Si-Si bond and eventually to heterolytic cleavage. Calculation results show that, in excess N-methylaniline, the final products of the reaction, including (NMePh)(3-n) SiHCl(n) (n=0-2) and (NMePh)(4-n) SiCl(n) (n=2-3), are the Si-Si cleavage products of Si2Cl6 and the corresponding amination products of the former. The ionic S(N)i-Si nucleophilic substitution mechanism can also be employed to describe the amination of chlorosilane by N-methylaniline. The suggested mechanisms are consistent with experimental data. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Mineralogy, provenance, and diagenesis of a potassic basaltic sandstone on Mars: CheMin X‐ray diffraction of the Windjana sample (Kimberley area, Gale Crater)

    Science.gov (United States)

    Bish, David L.; Vaniman, David T.; Chipera, Steve J.; Blake, David F.; Ming, Doug W.; Morris, Richard V.; Bristow, Thomas F.; Morrison, Shaunna M.; Baker, Michael B.; Rampe, Elizabeth B.; Downs, Robert T.; Filiberto, Justin; Glazner, Allen F.; Gellert, Ralf; Thompson, Lucy M.; Schmidt, Mariek E.; Le Deit, Laetitia; Wiens, Roger C.; McAdam, Amy C.; Achilles, Cherie N.; Edgett, Kenneth S.; Farmer, Jack D.; Fendrich, Kim V.; Grotzinger, John P.; Gupta, Sanjeev; Morookian, John Michael; Newcombe, Megan E.; Rice, Melissa S.; Spray, John G.; Stolper, Edward M.; Sumner, Dawn Y.; Vasavada, Ashwin R.; Yen, Albert S.

    2016-01-01

    Abstract The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X‐ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, ~Or95); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (~25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X‐ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations—like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser‐Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K‐rich targets have 5.6% K2O, ~1.8 times that of Windjana, implying a sediment component with >40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K‐rich sediment component is consistent with APXS and ChemCam observations of K‐rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g., mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar‐age terranes on Earth. PMID:27134806

  11. Issues relating to classification of colluvial soils in young morainic areas (Chełmno and Brodnica Lake District, northern Poland

    Directory of Open Access Journals (Sweden)

    Świtoniak Marcin

    2015-06-01

    Full Text Available Colluvial soils (in Polish: gleby deluwialne are an important part of the soil cover in young morainic landscapes of northern Poland. They evolved as a result of the accumulation of eroded material at the foot of the slopes and bottoms of closed depressions. The aim of this study was to determine the systematic position of colluvial soils commonly found in the Chełmno and Brodnica Lake District, northern Poland. Ten soil pits located in different types of landscapes were selected for testing soil properties. The colluvial material is characterized by diversified properties: thickness, particle-size distribution, organic carbon content, color, pH, and base saturation. As a result, the investigated soils represent broad spectrum of typological units according to Polish Soil Classification (2011. Some of them contain epipedons mollic and meet the criteria of colluvial chernozemic soils. They were found mainly on buried black earths in areas with small slope inclinations. Many pedons contain pale colored acidic colluvial material with low base saturation and low organic carbon content and must be classified as other types: arenosols (in Polish: arenosole or rusty soils (in Polish: gleby rdzawe. These soils occur mostly in areas with intensive relief and overlay the different soil types, including rusty soil and organic soils. They are formed as a result of soils lessivés and rusty soils truncation. An introduction of the additional units of “proper colluvial soils” which have epipedon ochric, and “rusty-colluvial soils” with endopedon sideric to the next edition of Polish Soil Classification would enable a more precise expression of the genesis of these soils in the type rank. Moreover, the definition of chernozemic colluvial soils could be extended to colluvial soils with umbric horizon. Classifying soils derived from colluvial material as soils of other types leads to the disappearance of this units on maps and underestimation of the

  12. Mineralogy, provenance, and diagenesis of a potassic basaltic sandstone on Mars: CheMin X-ray diffraction of the Windjana sample (Kimberley area, Gale Crater).

    Science.gov (United States)

    Treiman, Allan H; Bish, David L; Vaniman, David T; Chipera, Steve J; Blake, David F; Ming, Doug W; Morris, Richard V; Bristow, Thomas F; Morrison, Shaunna M; Baker, Michael B; Rampe, Elizabeth B; Downs, Robert T; Filiberto, Justin; Glazner, Allen F; Gellert, Ralf; Thompson, Lucy M; Schmidt, Mariek E; Le Deit, Laetitia; Wiens, Roger C; McAdam, Amy C; Achilles, Cherie N; Edgett, Kenneth S; Farmer, Jack D; Fendrich, Kim V; Grotzinger, John P; Gupta, Sanjeev; Morookian, John Michael; Newcombe, Megan E; Rice, Melissa S; Spray, John G; Stolper, Edward M; Sumner, Dawn Y; Vasavada, Ashwin R; Yen, Albert S

    2016-01-01

    The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X-ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, ~Or95); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (~25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X-ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations-like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser-Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K-rich targets have 5.6% K2O, ~1.8 times that of Windjana, implying a sediment component with >40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K-rich sediment component is consistent with APXS and ChemCam observations of K-rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g., mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar-age terranes on Earth.

  13. Prevalence of cirrhosis in hepatitis C patients in the Chronic Hepatitis Cohort Study (CHeCS): a retrospective and prospective observational study.

    Science.gov (United States)

    Gordon, Stuart C; Lamerato, Lois E; Rupp, Loralee B; Holmberg, Scott D; Moorman, Anne C; Spradling, Philip R; Teshale, Eyasu; Xu, Fujie; Boscarino, Joseph A; Vijayadeva, Vinutha; Schmidt, Mark A; Oja-Tebbe, Nancy; Lu, Mei

    2015-08-01

    The severity of liver disease in the hepatitis C virus (HCV)-infected population in the United States remains uncertain. We estimated the prevalence of cirrhosis in adults with chronic hepatitis C (CHC) using multiple parameters including liver biopsy, diagnosis/procedure codes, and a biomarker. Patients enrolled in the Chronic Hepatitis Cohort Study (CHeCS) who received health services during 2006-2010 were included. Cirrhosis was identified through liver biopsy reports, diagnosis/procedure codes for cirrhosis or hepatic decompensation, and Fibrosis-4 (FIB-4) scores ≥5.88. Demographic and clinical characteristics associated with cirrhosis were identified through multivariable logistic modeling. Among 9,783 patients, 2,788 (28.5%) were cirrhotic by at least one method. Biopsy identified cirrhosis in only 661 (7%) patients, whereas FIB-4 scores and diagnosis/procedure codes for cirrhosis and hepatic decompensation identified cirrhosis in 2,194 (22%), 557 (6%), and 482 (5%) patients, respectively. Among 661 patients with biopsy-confirmed cirrhosis, only 356 (54%) had an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for cirrhosis. Older age, male gender, Asian race, Hispanic ethnicity, genotype 3 infection, HIV coinfection, diabetes, history of antiviral therapy, and history of alcohol abuse were independently associated with higher odds of cirrhosis (all, P<0.05). Conversely, private health insurance coverage, black race, and HCV genotype 2 were associated with lower odds of cirrhosis. A high proportion of patients with biopsy-confirmed cirrhosis are not assigned ICD-9 codes for cirrhosis. Consequently, ICD-9 codes may not be reliable as the sole indicator of the prevalence of cirrhosis in cohort studies. Use of additional parameters suggests a fourfold higher prevalence of cirrhosis than is revealed by biopsy alone. These findings suggest that cirrhosis in CHC patients may be significantly underdocumented and

  14. Quantum wells based on Si/SiO{sub x} stacks for nanostructured absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Berghoff, B.; Suckow, S.; Roelver, R.; Spangenberg, B.; Kurz, H. [Institute of Semiconductor Electronics, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); Sologubenko, A.; Mayer, J. [Central Facility for Electron Microscopy, RWTH Aachen University, Ahornstr. 55, 52074 Aachen (Germany); Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons, Research Centre Juelich, 52426 Juelich (Germany)

    2010-11-15

    We report on electrical transport and quantum confinement in thermally annealed Si/SiO{sub x} multiple quantum well (QW) stacks. Results are correlated with the morphology of the stacks. High temperature annealing of Si/SiO{sub x} stacks leads to precipitation of excess Si from the SiO{sub x} layers, which enhances the degree of crystallization and increases the grain sizes in the Si QWs compared to the conventional Si/SiO{sub 2} system. Moreover, the excess Si forms highly conductive pathways between adjacent Si QWs that are separated by ultrathin silicon oxide barriers. This results in an increase of conductivity by up to 10 orders of magnitude compared to the tunneling dominated transport in Si/SiO{sub 2} stacks. The stacks exhibit a distinct quantum confinement as confirmed by photoluminescence measurements. (author)

  15. Modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yuying [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China)], E-mail: wyy532001@163.com; Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602, Shandong (China); Jiang Binggang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Huang Chuanzhen [School of Mechanical Engineering, Shandong University, Jinan 250061 (China)

    2009-05-27

    Modification effect of Ni-38 wt.%Si on the Al-12 wt.%Si alloy has been studied by differential scanning calorimeter, torsional oscillation viscometer and liquid X-ray diffraction experiments. It is found that there is a modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy, i.e. primary Si can precipitate in the microstructure of Al-12 wt.%Si alloy when Ni and Si added in the form of Ni-38 wt.%Si, but not separately. Ni-38 wt.%Si alloy brings 'genetic materials' into the Al-Si melt, which makes the melt to form more ordering structure, promotes the primary Si precipitated. Moreover, the addition of Ni-38 wt.%Si, which decreases the solidification supercooling degree of Al-12 wt.%Si alloy, is identical to the effect of heterogeneous nuclei.

  16. L’immagine che appare

    Directory of Open Access Journals (Sweden)

    Giovanni Matteucci

    2012-05-01

    Full Text Available It’s a matter of fact that images are not taken for signs. Therefore there must be some intrinsic peculiarity, which allows them to convey a content but, in the same breath, prevents them from collapsing into mere semiotic structures. Such a feature could lie in a sort of “semblance grammar”, which gives off the perceptual potential of images, and reveals itself in the experience before any determination of an ontological status. It’s in the way the image appears that the power of the image to articulate fruitfully a thought manifests itself.

  17. Effect of starting composition on formation of MoSi2–SiC ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 35; Issue 4. Effect of starting ... MoSi2–SiC nanocomposite powders were successfully synthesized by ball milling Mo, Si and graphite elemental powders. Effects of ... Mo5Si3 was formed during annealing as a product of a reaction between MoSi2 and excess graphite.

  18. Current–voltage studies on β-FeSi2/Si heterojunction

    Indian Academy of Sciences (India)

    – characteristics of both -FeSi2/n-Si and -FeSi2/p-Si were studied at room temperature. The junctions were formed by depositing Fe on Si selectively followed by thermal annealing and some samples were later treated by pulsed laser. Temperature of thermal annealing and diode area were also varied. – studies ...

  19. Mo-Si alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Heatherly, L.; Wright, J.L. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  20. Analysis of Si/SiGe Heterostructure Solar Cell

    Directory of Open Access Journals (Sweden)

    Ashish Kumar Singh

    2014-01-01

    Full Text Available Sunlight is the largest source of carbon-neutral energy. Large amount of energy, about 4.3 × 1020 J/hr (Lewis, 2005, is radiated because of nuclear fusion reaction by sun, but it is unfortunate that it is not exploited to its maximum level. Various photovoltaic researches are ongoing to find low cost, and highly efficient solar cell to fulfil looming energy crisis around the globe. Thin film solar cell along with enhanced absorption property will be the best, so combination of SiGe alloy is considered. The paper presented here consists of a numerical model of Si/Si1-xGex heterostructure solar cell. The research has investigated characteristics such as short circuit current density (Jsc, generation rate (G, absorption coefficient (α, and open circuit voltage (Voc with optimal Ge concentration. The addition of Ge content to Si layer will affect the property of material and can be calculated with the use of Vegard’s law. Due to this, short circuit current density increases.

  1. High-Temperature, Perhaps Silicic, Volcanism on Mars Evidenced by Tridymite Detection in High-SiO2 Sedimentary Rock at Gale Crater, Mars

    Science.gov (United States)

    Morris, R. V.; Vaniman, D. T.; Blake, D. F.; Gellert, R.; Chipera, S. J.; Rampe, E. B.; Ming, D. W.; Morrison, S. M.; Downs, R. T.; Treiman, A. H.; hide

    2016-01-01

    The Mars Science Laboratory (MSL) rover, Curiosity, has been exploring sedimentary rocks within Gale crater since landing in August, 2012. On the lower slopes of Aeolis Mons (a.k.a. Mount Sharp), drill powder was collected from a high-silica (74 wt% SiO2) outcrop named Buckskin (BK). It was a surprise to find that the Buckskin sample contained significant amounts of the relatively rare silica polymorph tridymite. We describe the setting of the Buckskin sample, the detection of tridymite by the MSL Chemistry and Mineralogy (CheMin) X-ray diffraction instrument, and detection implications. Geologic setting: The Buckskin outcrop is part of the Murray formation exposed in the Marias Pass area. The formation was previously studied by CheMin in the Pahrump Hills member [1] where three samples of drill fines were analyzed (Confidence Hills (CH), Mojave2 (MJ) and Telegraph Peak (TP) [2]). Assuming approximately horizontal bedding, the Buckskin outcrop is approx.15 m stratigraphically above the bottom of the Pahrump Hills member. Mudstone, generally characterized by fine lamination, is the dominant depositional facies [1]. Buckskin Mineralogical and Chemical Composition: The CheMin instrument and XRD pattern analysis procedures have been previously discussed [3-6]. The diffraction pattern used for quantitative XRD analysis (Fig. 1) is the sum of the first 4 of 45 diffraction images. The remaining images are all characterized by both on-ring and off-ring diffraction spots that we attributed to poor grain motion and particle clumping. Coincident with particle clumping was a significant decrease in the intensity of the tridymite diffraction peaks (Fig. 2a). The derived mineralogical composition of the crystalline component (derived from the first 4 diffraction images) is given in Table 1. The tridymite is well-crystalline and its pattern is refined as monoclinic tridymite (Fig 1). Mineral chemical compositions were derived from XRD unit cell parameters or obtained from

  2. Influence of CrSi2 nanocrystals on the electrical properties of Au/Si - p/CrSi2 NCs/Si(111) - n mesa-diodes

    Science.gov (United States)

    Galkin, Nikolay G.; Dózsa, Laszlo; Chusovitin, Evgenii A.; Dotsenko, Sergey A.; Pécz, Bela; Dobos, Laszlo

    Semiconducting CrSi2 nanocrystals (NCs) with high density (4×1010 cm-2) and narrow size distribution were grown by reactive deposition epitaxy (RDE) of 0.6 nm Cr at 550 °C on Si(111)7 × 7 substrate. Based on DRS, AFM and TEM results silicon cap epitaxy growth procedure on silicon with high density of CrSi2 NCs has been proposed. Monolithic Si(111)/ CrSi2 NCs/Si(111) structures with three layers of buried CrSi2 NCs have been successfully grown by repeating of CrSi2 NCs formation and silicon epitaxial growth. Electrical characterization of Schottky junctions formed on the grown structures has shown that the formation of point defects generated during the growth of the Si cap layer strongly depends on the cap growth conditions and on the Cr deposition rate.

  3. «Si torni pure all'asino». L'asino d'oro di Apuleio (la traduzione, le traduzioni, gli intraducibili

    Directory of Open Access Journals (Sweden)

    Monica Longobardi

    2013-12-01

    Full Text Available È noto che la lingua di Apuleio sia ricchissima di effetti anfibologici e paronomastici. Come tradurre? In questo saggio si esaminano due diverse traduzioni, quella emulativa di Alessandro Fo e quella ‘servile’ di Lara Nicolini. In alcuni dei copiosissimi loci bollati come ‘intraducibili’, l’autrice di questo saggio offre proposte e soluzioni che limitino l’ineluttabilità di tale sconfitta, valorizzando in traduzione la dominante ludica dello stile delle Metamorfosi di Apuleio.Apuleius’ language is well-known for its wealth of amphibological and paronomastic effects. How should it be translated? This essay examines two different solutions: Alessando Fo’s translation, which seeks to produce similar effects, and Lara Nicolini’s one, aimed at formal equivalence. For a few of the many 'untranslatable' text passages, the author of this essay offers possible solution to limit the ineluctability of this defeat and to best render the ludic dominant of Apuleius’s style in the Metamorphoses.

  4. Microwave joining of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Silberglitt, R.; Ahmad, I.; Tian, Y.L. [FM Technologies, Inc., Fairfax, VA (United States)] [and others

    1997-04-01

    The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on identification of the most effective joining methods for scale-up to large tube assemblies, including joining using SiC produced in situ from chemical precursors. During FY 1996, a new microwave applicator was designed, fabricated and tested that provides the capability for vacuum baking of the specimens and insulation and for processing under inert environment. This applicator was used to join continuous fiber-reinforced (CFCC) SiC/SiC composites using a polymer precursor to form a SiC interlayer in situ.

  5. Measurements for Cu and Si diffusivities in Al-Cu-Si alloys by diffusion couples

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Dingfei [College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China)]. E-mail: zhangdingfei@cqu.edu.cn; Morral, John E. [Department of Materials Science and Engineering, Ohio State University, OH 43210 (United States); Brody, Harold D. [Institute of Materials Science, University of Connecticut, CT 06268 (United States)

    2007-02-25

    This paper deals with diffusivity measurements for Cu and Si atoms in Al-Cu-Si alloys by diffusion couples. With Cu and Si concentration profiles in the diffusion couples treated by different heating temperatures and times, their diffusivities including D {sub CuCu}, D {sub SiSi}, D {sub CuSi} and D {sub SiCu} in Al-Cu-Si ternary alloys could be calculated and their D {sub 0} and Q also could be obtained by their diffusivities under different temperatures.

  6. Using SI Units in Astronomy

    Science.gov (United States)

    Dodd, Richard

    2011-12-01

    1. Introduction; 2. An introduction to SI units; 3. Dimensional analysis; 4. Unit of angular measure (radian); 5. Unit of time (second); 6. Unit of length (metre); 7. Unit of mass (kilogram); 8. Unit of luminous intensity (candela); 9. Unit of thermodynamic temperature (kelvin); 10. Unit of electric current (ampere); 11. Unit of amount of substance (mole); 12. Astronomical taxonomy; Index.

  7. The HFIR 14J irradiation SiC/SiC composite and SiC fiber collaboration

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira; Katoh, Yutai [Kyoto Univ., Uji, Kyoto (Japan); Hasegawa, Akira [Tohoku Univ., Aramaki, Sendai (Japan); Snead, L. [Oak Ridge National Lab., TN (United States); Scholz, R.

    1998-09-01

    A short introduction with references establishes the current status of research and development of SiC{sub f}/SiC composites for fusion energy systems with respect to several key issues. The SiC fiber and composite specimen types selected for the JUPITER 14J irradiation experiment are presented together with the rationale for their selection.

  8. Proton trapping at the Si/SiO2 interface studied by first-principles method

    Science.gov (United States)

    Zhang, Qiming; Tang, Shaoping; Wallace, R. M.; Archer, L.

    1998-03-01

    The behavior of mobile protons at the Si/SiO2 interface has drawn substantial interests since it was found to play the critical role in a proposed non-volatile memory device based on Si/SiO_2/Si structures(K. Vanheusden et al.), Nature 386, 587 (1997). We have investigated the bonding and diffusion properties of a proton at the interface by first-principles local density cluster total energy approach (DMol). A 73 atom cluster model is used to simulate the Si/SiO2 interface which is constructed from beta-cristobalite SiO2 on Si(001) surface. In agreement with previous calculation of proton in bulk Si, the Si-Si bond center is found to be a stable site for proton on the Si side. On the SiO2 side, proton is found to bond with O atoms. The energy for the proton at corresponding binding sites decreases while the proton penetrate into the oxide, forming an energy well which confines protons in oxide in a Si/SiO_2/Si structure. The diffusion barrier for a proton hopping between the neighboring binding sites is 0.73 eV, in good agreement with the experimental activation energy ( 0.8 eV)^1.

  9. Dose evaluation for workers employed in an industry involving enamel paints containing zirconium silicate; Valutazione di dose per i lavoratori occupati in una industria che utilizza vernici a smalto contenenti silicato di zirconio

    Energy Technology Data Exchange (ETDEWEB)

    Castellani, C.M.; Berico, M.; De Zaiacomo, T.; Formignani, M.; Ianni, A.; Nobili, C.; Sandri, S.; Vasselli, R. [ENEA, Centro Ricerche Ezio Clementel, Bologna (Italy). Dipt. Ambiente

    1999-07-01

    In the frame of the European Recommendations for radiological protection, an evaluation of the annual dose has been made for workers employed in an industry for the production of sanitary equipment involving the use of enamel paints containing zirconium silicate. [Italian] Nella prospettiva dell'applicazione della direttiva europea relativa alla protezione radiologica dei lavoratori, vengono presentati i risultati relativi alla valutazione di dose annuale complessiva per i lavoratori occupati in una industria per la produzione di articoli igienico-sanitari che utilizza vernici a smalto contenenti silicato di zirconio. Il fine e' la valutazione del problema radioprotezionistico per gli addetti a causa delle impurezza radioattive presenti nei materiali utlizzati.

  10. 3C-SiC nanocrystal growth on 10° miscut Si(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Deokar, Geetanjali, E-mail: gitudeo@gmail.com [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); D' Angelo, Marie; Demaille, Dominique [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Cavellin, Catherine Deville [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Faculté des Sciences et Technologie UPEC, 61 av. De Gaulle, Créteil F-94010 (France)

    2014-04-01

    The growth of 3C-SiC nano-crystal (NC) on 10° miscut Si(001) substrate by CO{sub 2} thermal treatment is investigated by scanning and high resolution transmission electron microscopies. The vicinal Si(001) surface was thermally oxidized prior to the annealing at 1100 °C under CO{sub 2} atmosphere. The influence of the atomic steps at the vicinal SiO{sub 2}/Si interface on the SiC NC growth is studied by comparison with the results obtained for fundamental Si(001) substrates in the same conditions. For Si miscut substrate, a substantial enhancement in the density of the SiC NCs and a tendency of preferential alignment of them along the atomic step edges is observed. The SiC/Si interface is abrupt, without any steps and epitaxial growth with full relaxation of 3C-SiC occurs by domain matching epitaxy. The CO{sub 2} pressure and annealing time effect on NC growth is analyzed. The as-prepared SiC NCs can be engineered further for potential application in optoelectronic devices and/or as a seed for homoepitaxial SiC or heteroepitaxial GaN film growth. - Highlights: • Synthesis of 3C-SiC nanocrystals epitaxied on miscut-Si using a simple technique • Evidence of domain matching epitaxy at the SiC/Si interface • SiC growth proceeds along the (001) plane of host Si. • Substantial enhancement of the SiC nanocrystal density due to the miscut • Effect of the process parameters (CO{sub 2} pressure and annealing duration)

  11. The influence of strain on the diffusion of Si dimers on Si(001)

    NARCIS (Netherlands)

    Zoethout, E.; Zoethout, E.; Gurlu, O.; Gürlü, O.; Zandvliet, Henricus J.W.; Poelsema, Bene

    2000-01-01

    The influence of lattice mismatch-induced tensile strain on the diffusion of Si dimers on Si(001) has been studied. The rate of surface diffusion of a Si dimer along the substrate dimer rows is relatively insensitive to tensile strain, whereas the rate of diffusion for a Si dimer across the

  12. A sensitive optical sensor based on DNA-labelled Si@SiO2 core ...

    Indian Academy of Sciences (India)

    2017-10-31

    Oct 31, 2017 ... fluorescent assay based on DNA-labelled Si@SiO2 core–shell nanoparticles for the detection of mercury (II) in environmental samples was investigated. Probe DNA was conjugated on the surface of the Si@SiO2 core–shell nanoparticles via 5 - terminal-SH (thiol group) reaction. The detection protocol was ...

  13. Preparation of Si3N4–SiC composites by microwave route

    Indian Academy of Sciences (India)

    Unknown

    composited the creep resistance has also been reported to improve (Niihara et al 1990; Hirano et al 1996; Rendtel et al 1998; Yamada and Kamiya 1999). Possibilities of making engine components using Si3N4–SiC composites have been discussed in the literature. Si3N4–SiC compo- sites can be designed and sintered ...

  14. Laser cladding of Al-Si/SiC composite coatings : Microstructure and abrasive wear behavior

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J.Th.M.

    2007-01-01

    Surface coatings of an Al-Si-SiC composite were produced on UNS A03560 cast Al-alloy substrates by laser cladding using a mixture of powders of Al-12 wt.% Si alloy and SiC. The microstructure of the coatings depends considerably on the processing parameters. For a specific energy of 26 MJ/m2 the

  15. Location and Electronic Nature of Phosphorus in the Si Nanocrystal--SiO2 System.

    Science.gov (United States)

    König, Dirk; Gutsch, Sebastian; Gnaser, Hubert; Wahl, Michael; Kopnarski, Michael; Göttlicher, Jörg; Steininger, Ralph; Zacharias, Margit; Hiller, Daniel

    2015-05-22

    Up to now, no consensus exists about the electronic nature of phosphorus (P) as donor for SiO2-embedded silicon nanocrystals (SiNCs). Here, we report on hybrid density functional theory (h-DFT) calculations of P in the SiNC/SiO2 system matching our experimental findings. Relevant P configurations within SiNCs, at SiNC surfaces, within the sub-oxide interface shell and in the SiO2 matrix were evaluated. Atom probe tomography (APT) and its statistical evaluation provide detailed spatial P distributions. For the first time, we obtain ionisation states of P atoms in the SiNC/SiO2 system at room temperature using X-ray absorption near edge structure (XANES) spectroscopy, eliminating structural artefacts due to sputtering as occurring in XPS. K energies of P in SiO2 and SiNC/SiO2 superlattices (SLs) were calibrated with non-degenerate P-doped Si wafers. results confirm measured core level energies, connecting and explaining XANES spectra with h-DFT electronic structures. While P can diffuse into SiNCs and predominantly resides on interstitial sites, its ionization probability is extremely low, rendering P unsuitable for introducing electrons into SiNCs embedded in SiO2. Increased sample conductivity and photoluminescence (PL) quenching previously assigned to ionized P donors originate from deep defect levels due to P.

  16. SiO adsorption on a p(2 × 2) reconstructed Si(1 0 0) surface

    NARCIS (Netherlands)

    Violanda, M.|info:eu-repo/dai/nl/304840262; Rudolph, H.|info:eu-repo/dai/nl/304830496

    2009-01-01

    We have investigated the adsorption mechanism of SiO molecule incident on a clean Si(1 0 0) p(2 × 2) reconstructed surface using density functional theory based methods. Stable adsorption geometries of SiO on Si surface, as well as their corresponding activation and adsorption energies are

  17. Growth of Au-catalysed Si nanowires by low pressure chemical vapour deposition on Si(100) and amorphous Si surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Santoni, A; Villacorta, F Jimenez; Rufoloni, A; Mancini, A [ENEA C.R. Frascati, v. E. Fermi 45, I-00044 Frascati (Italy)

    2006-12-06

    Au-mediated Si nanowires (SiNW) have been grown at low temperatures (500-560 {sup 0}C) on crystalline Si(100) and amorphous Si surfaces by means of low pressure chemical vapour deposition from Si{sub 2}H{sub 6} in the 0.05-1.2 mbar range. The influence of the substrates on the nanowire (NW) growth and morphology has been investigated by means of x-ray photoelectron spectroscopy and scanning electron microscopy. No NW growth has been observed on the Au covered amorphous Si surfaces. On both substrates, the NW exhibit inhomogeneous sidewalls and a new morphology showing NW entrenchment which has been explained as a consequence of vapour-liquid-solid growth termination due to Au diffusion on the SiNW sidewalls.

  18. Financial balance of the recovery of energy starting from the thermal-destruction; Bilancio economico del recupero di energia dalla termodistruzione

    Energy Technology Data Exchange (ETDEWEB)

    Macchi, E. [Milan Politecnico, Milan (Italy). Dipt. Energetica

    2000-08-01

    elettrica installata, alla produzione elettrica lorda e al contributo fornito dagli RSU al teleriscaldamento. Si indicano quindi le principali grandezze che intervengono nelle valutazioni economiche (costi di investimento, vita utile dell'impianto, indici economici, tempi di realizzazione, costi operativi, rendimenti, affidabilita' e disponibilita' dell'impianto, valorizzazione dell'energia elettrica e termica generata, ricavi da smaltimento rifiuti), evidenziando l'importanza della taglia dell'impianto, che e' il vero fattore decisivo. Vengono prodotti esempi esplicativi del peso dei diversi fattori. In particolare, viene approfondito il ruolo dell'energia prodotta da RSU nel nuovo mercato elettrico liberalizzato, evidenziandone i vantaggi rispetto all'energia da fonti convenzionali. Si discutono infine le potenzialita' di impianti <>, che coniugano l'incenerimento degli RSU alla tecnologia dei cicli combinati alimentati da gas naturale.

  19. Enhancement of thermoelectric power factor in CrSi2 film via Si:B addition

    Science.gov (United States)

    Hou, Q. R.; Gu, B. F.; Chen, Y. B.

    2015-09-01

    In this paper, we report a large enhancement in the thermoelectric power factor in CrSi2 film via Si:B (1 at.% B content) addition. The Si:B-enriched CrSi2 films are prepared by co-sputtering CrSi2 and heavily B-doped Si targets. Both X-ray diffraction patterns and Raman spectra confirm the formation of the crystalline phase CrSi2. Raman spectra also indicate the crystallization of the added Si:B. With the addition of Si:B, the electrical resistivity (R) decreases especially at low temperatures while the Seebeck coefficient (S) increases above 533 K. As a result, the thermoelectric power factor, PF = S2/R, is greatly enhanced and can reach 716 × 10-6W/m ṡK2 at 583 K, which is much larger than that of the pure CrSi2 film.

  20. Abrupt GaP/Si hetero-interface using bistepped Si buffer

    Energy Technology Data Exchange (ETDEWEB)

    Ping Wang, Y., E-mail: yanping.wang@insa-rennes.fr; Kuyyalil, J.; Nguyen Thanh, T.; Almosni, S.; Bernard, R.; Tremblay, R.; Da Silva, M.; Létoublon, A.; Rohel, T.; Tavernier, K.; Le Corre, A.; Cornet, C.; Durand, O. [UMR FOTON, CNRS, INSA Rennes, Rennes F-35708 (France); Stodolna, J.; Ponchet, A. [CEMES-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 04 (France); Bahri, M.; Largeau, L.; Patriarche, G. [Laboratoire de Photonique et Nanostructures, CNRS UPR 20, Route de Nozay, Marcoussis 91460 (France); Magen, C. [LMA, INA-ARAID, and Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018 Zaragoza (Spain)

    2015-11-09

    We evidence the influence of the quality of the starting Si surface on the III-V/Si interface abruptness and on the formation of defects during the growth of III-V/Si heterogeneous crystal, using high resolution transmission electron microscopy and scanning transmission electron microscopy. GaP layers were grown by molecular beam epitaxy on vicinal Si (001). The strong effect of the Si substrate chemical preparation is first demonstrated by studying structural properties of both Si homoepitaxial layer and GaP/Si heterostructure. It is then shown that choosing adequate chemical preparation conditions and subsequent III-V regrowth conditions enables the quasi-suppression of micro-twins in the epilayer. Finally, the abruptness of GaP/Si interface is found to be very sensitive to the Si chemical preparation and is improved by the use of a bistepped Si buffer prior to III-V overgrowth.

  1. Misfit dislocation locking and rotation during gallium nitride growth on SiC/Si substrates

    Science.gov (United States)

    Kukushkin, S. A.; Osipov, A. V.; Bessolov, V. N.; Konenkova, E. V.; Panteleev, V. N.

    2017-04-01

    The effect of changing the misfit dislocation propagation direction during GaN layer growth on the AlN/SiC/Si(111) structure surface is detected. The effect is as follows. As the GaN layer growing on AlN/SiC/Si(111) reaches a certain thickness of 300 nm, misfit dislocations initially along the layer growth axis stop and begin to move in the direction perpendicular to the growth axis. A theoretical model of AlN and GaN nucleation on the (111) SiC/Si face, explaining the effect of changing the misfit dislocation motion direction, is constructed. The effect of changing the nucleation mechanism from the island one for AlN on SiC/Si(111) to the layer one for the GaN layer on AlN/SiC/Si is experimentally detected and theoretically explained.

  2. Effect of Si interface surface roughness to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor

    Energy Technology Data Exchange (ETDEWEB)

    Hasanah, Lilik, E-mail: lilikhasanah@upi.edu; Suhendi, Endi; Tayubi, Yuyu Rahmat; Yuwono, Heru [Department of Physics Education, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Nandiyanto, Asep Bayu Dani [Department Kimia, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Murakami, Hideki [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan); Khairrurijal [Physics of Electronic Materials Research Division, Institut Teknologi Bandung, Bandung 40132 (Indonesia)

    2016-02-08

    In this work we discuss the surface roughness of Si interface impact to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor. The Si interface surface roughness can be analyzed from electrical characteristics through the transversal electron velocity obtained as fitting parameter factor. The results showed that surface roughness increase as Ge content of virtual substrate increase This model can be used to investigate the effect of Ge content of the virtual substrate to the interface surface condition through current-voltage characteristic.

  3. Formation of Si/SiC multilayers by low-energy ion implantation and thermal annealing

    NARCIS (Netherlands)

    Dobrovolskiy, S.; Yakshin, A.E.; Yakshin, Andrey; Tichelaar, F.D.; Verhoeven, J.; Louis, E.; Louis, Eric; Bijkerk, Frederik

    2010-01-01

    Si/SiC multilayer systems for XUV reflection optics with a periodicity of 10–20 nm were produced by sequential deposition of Si and implantation of 1 keV View the MathML source ions. Only about 3% of the implanted carbon was transferred into the SiC, with a thin, 0.5–1 nm, buried SiC layer being

  4. Si

    African Journals Online (AJOL)

    similar, the prevalence of helminthiasis was high in Dawaro and Guragie ethnic groups which may be due to difference in living habit that needs further investigation. As other studies showed (21), logically as well, those from analphabet mother and low income family should have more intestinal parasitosis because of the.

  5. Cathodoluminescence studies on GaN on Si(211) and Si(311) substrates; Kathodolumineszenzuntersuchungen an GaN auf Si(211)- und Si(311)-Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Mathias; Dempewolf, Anja; Bertram, Frank; Hempel, Thomas; Christen, Juergen; Ravash, Roghaiyeh; Dadgar, Armin; Krost, Alois [Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet Magdeburg (Germany)

    2011-07-01

    Spectrally resolved cathodoluminescence measurements were used to study GaN layers on Si(211) and Si(311 substrates at liquid helium temperatures. Non-c axis oriented GaN growth allows a reduction of polarization fields and thus the quantum confined Stark effect (QCSE) that reduces the efficiency of optoelectronic devices. The authors used appropriated high-indices Si(h11) substrates with a MOVPE grown AlN seed layer and an AlGaN buffer layer, two thick GaN layers with an AlN interlayer. The low-temperature luminescence spectra showed three dominant luminescence channels: the bound exciton D(0),X), donor-acceptor pairs (DAP) and basal plane stacking faults luminescence. The stacking fault luminescence on Si(211) is significantly reduced compared to GaN on Si(311). The results indicate a strong inhomogeneity of Si(311) compared to Si(211).

  6. Preparation of biomorphic SiC ceramics

    Directory of Open Access Journals (Sweden)

    Egelja A.

    2008-01-01

    Full Text Available This paper deals with a new method for producing non-oxide ceramic using wood as a template. SiC with a woodlike microstructure has been prepared by carbothermal reduction reactions of Tilia wood/TEOS composite at 1873K. The porous carbon preform was infiltrated with TEOS (Si(OC2H54, as a source of silica, without pressure at 298K. The morphology of resulting porous SiC ceramics, as well as the conversion mechanism of wood to SiC ceramics, have been investigated by scanning electron microscopy (SEM/EDS and X-ray diffraction analysis (XRD. Obtained SiC ceramics consists of β-SiC with traces of α-SiC.

  7. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Liu Jian

    2009-01-01

    Full Text Available Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  8. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays.

    Science.gov (United States)

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-10-29

    Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  9. Nucleation and void formation mechanisms in SiC thin film growth on Si by carbonization

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.P.; Steckl, A.J. [Univ. of Cincinnati, OH (United States)

    1995-02-01

    The nucleation mechanisms for SiC thin films on Si were investigated by interrupting the growth at very brief times ({approximately}1 to 10 s) using rapid thermal chemical vapor deposition in conjunction with hydrocarbon carbonization. The resulting SiC nuclei and films on Si have been studied by scanning electron microscopy and atomic force microscopy. The hydrocarbon partial pressure in the gas stream was found to determine the nucleation mode. Low precursor concentration results in initial three-dimensional (island) growth which enables the study or trench and void formation. Voids were observed to initiate when two neighboring nuclei come in contact. Trenches in the Si substrate surround each isolated nucleus, with the trench depth increasing with the diameter of the island. SiC films grown for a nominal reaction time of 1 s indicate that increasing the propane concentration results in decreases in SiC grain size and surface roughness and an increase in the nuclei density. A model is proposed for the nucleation process of SiC growth on Si by carbonization consisting of the following key steps: (1) the initial nucleation density is determined by the precursor concentration; (2) lateral and vertical growth of individual nuclei proceeds by consumption of Si atoms around their periphery, forming trenches in the substrate; (3) Si voids are formed in the Si substrate near the SiC/Si interface when nuclei grow large enough to come in contact and, thus, restrict the supply of Si atoms.

  10. ‘Unkind and cruel, to deceive your Son | In borrow’d Shapes, and his Embrace to shun’: Mother-son love in T. S. Eliot’s ‘La Figlia Che Piange’

    Directory of Open Access Journals (Sweden)

    Matthew Geary

    2015-01-01

    Full Text Available T. S. Eliot's "La Figlia Che Piange" (1916 is a curious anomaly in his early works. It stands out as a love poem of outstanding grace portraying a more positive relationship to the feminine compared to other poems contemporaneous with its writing such as "The Love Song of St. Sebastian" (1914 and "Hysteria" (1915. This essay shows the import of Eliot's chosen epigraph for "La Figlia" taken from Virgil's Aeneid to have been largely neglected or misread by critics. As a consequence, it argues that critical readings have crucially missed the presence of a shrouded maternal aspect within the poem. Through the lens of Lacanian psychoanalysis and the work of adherents to Lacanian theory — such as Bruce Fink, Shoshana Felman and Slavoj Zizek — this paper newly argues that the poem's meditation on the issues of union and separation between two lovers is in fact a screen for deeper unconscious ambivalent feelings between mother and son. That is to say, Eliot's "La Figlia Che Piange" shows a failed attempt to reconstruct, traverse and separate from the "fundamental fantasy" unconsciously orientating the male speaker of the poem and his desire.

  11. Three-dimensional crossbar arrays of self-rectifying Si/SiO2/Si memristors

    Science.gov (United States)

    Li, Can; Han, Lili; Jiang, Hao; Jang, Moon-Hyung; Lin, Peng; Wu, Qing; Barnell, Mark; Yang, J. Joshua; Xin, Huolin L.; Xia, Qiangfei

    2017-06-01

    Memristors are promising building blocks for the next-generation memory and neuromorphic computing systems. Most memristors use materials that are incompatible with the silicon dominant complementary metal-oxide-semiconductor technology, and require external selectors in order for large memristor arrays to function properly. Here we demonstrate a fully foundry-compatible, all-silicon-based and self-rectifying memristor that negates the need for external selectors in large arrays. With a p-Si/SiO2/n-Si structure, our memristor exhibits repeatable unipolar resistance switching behaviour (105 rectifying ratio, 104 ON/OFF) and excellent retention at 300 °C. We further build three-dimensinal crossbar arrays (up to five layers of 100 nm memristors) using fluid-supported silicon membranes, and experimentally confirm the successful suppression of both intra- and inter-layer sneak path currents through the built-in diodes. The current work opens up opportunities for low-cost mass production of three-dimensional memristor arrays on large silicon and flexible substrates without increasing circuit complexity.

  12. Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, H.; Curtin, W.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)

    1996-08-01

    Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

  13. An Isotope Study of Hydrogenation of poly-Si/SiOx Passivated Contacts for Si Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Nemeth, William; van de Loo, Bas, W.H.; Macco, Bart; Kessels, Wilhelmus, M.M.; Stradins, Paul; Young, David, L.

    2017-06-26

    For many years, the record Si solar cell efficiency stood at 25.0%. Only recently have several companies and institutes managed to produce more efficient cells, using passivated contacts of made doped poly-Si or a-Si:H and a passivating intrinsic interlayer in all cases. Common to these designs is the need to passivate the layer stack with hydrogen. In this contribution, we perform a systematic study of passivated contact passivation by hydrogen, using poly-Si/SiOx passivated contacts on n-Cz-Si, and ALD Al2O3 followed by a forming gas anneal (FGA) as the hydrogen source. We study p-type and n-type passivated contacts with implied Voc exceeding 690 and 720 mV, respectively, and perform either the ALD step or the FGA with deuterium instead of hydrogen in order to separate the two processes via SIMS. By examining the deuterium concentration at the SiOx in both types of samples, we demonstrate that the FGA supplies negligible hydrogen species to the SiOx, regardless of whether the FGA is hydrogenated or deuterated. Instead, it supplies the thermal energy needed for hydrogen species in the Al2O3 to diffuse there. Furthermore, the concentration of hydrogen species at the SiOx can saturate while implied Voc continues to increase, showing that the energy from the FGA is also required for hydrogen species already at the SiOx to find recombination-active defects to passivate.

  14. Silicon Promotes Exodermal Casparian Band Formation in Si-Accumulating and Si-Excluding Species by Forming Phenol Complexes

    National Research Council Canada - National Science Library

    Fleck, Alexander T; Schulze, Sascha; Hinrichs, Martin; Specht, André; Waßmann, Friedrich; Schreiber, Lukas; Schenk, Manfred K

    2015-01-01

    We studied the effect of Silicon (Si) on Casparian band (CB) development, chemical composition of the exodermal CB and Si deposition across the root in the Si accumulators rice and maize and the Si non-accumulator onion...

  15. Impact Resistance of Uncoated SiC/SiC Composites

    Science.gov (United States)

    Bhatt, Ramakrishna T.; Choi, Sung R.; Cosgriff, Laura M.; Fox, Dennis S.; Lee, Kang N.

    2008-01-01

    Two-dimensional woven SiC/SiC composites fabricated by melt infiltration method were impact tested at room temperature and at 1316 C in air using 1.59-mm diameter steel-ball projectiles at velocities ranging from 115 to 400 m/s. The extent of substrate damage with increasing projectile velocity was imaged and analyzed using optical and scanning electron microscopy, and non-destructive evaluation (NDE) methods such as pulsed thermography, and computed tomography. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. Results indicate that at 115 m/s projectile velocity, the composite showed no noticeable surface or internal damage and retained its as-fabricated mechanical properties. As the projectile velocity increased above this value, the internal damage increased and mechanical properties degraded: At velocities >300 m/s, the projectile penetrated through the composite, but the composite retained approx.50% of the ultimate tensile strength of the as-fabricated composite and exhibited non-brittle failure. Predominant internal damages are delamination of fiber plies, fiber fracture and matrix shearing.

  16. Phase transformation in SiOx/SiO₂ multilayers for optoelectronics and microelectronics applications.

    Science.gov (United States)

    Roussel, M; Talbot, E; Pratibha Nalini, R; Gourbilleau, F; Pareige, P

    2013-09-01

    Due to the quantum confinement, silicon nanoclusters (Si-ncs) embedded in a dielectric matrix are of prime interest for new optoelectronics and microelectronics applications. In this context, SiO(x)/SiO₂ multilayers have been prepared by magnetron sputtering and subsequently annealed to induce phase separation and Si clusters growth. The aim of this paper is to study phase separation processes and formation of nanoclusters in SiO(x)/SiO₂ multilayers by atom probe tomography. Influences of the silicon supersaturation, annealing temperature and SiO(x) and SiO₂ layer thicknesses on the final microstructure have been investigated. It is shown that supersaturation directly determines phase separation regime between nucleation/classical growth and spinodal decomposition. Annealing temperature controls size of the particles and interface with the surrounding matrix. Layer thicknesses directly control Si-nc shapes from spherical to spinodal-like structures. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Formation of high-density Si nanodots by agglomeration of ultra-thin amorphous Si films

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, Hiroki [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)], E-mail: hkondo@alice.xtal.nagoya-u.ac.jp; Ueyama, Tomonori [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ikenaga, Eiji; Kobayashi, Keisuke [Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Sakai, Akira [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ogawa, Masaki [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2008-11-03

    High-density and similarly-sized Si nanodots were formed by annealing ultra-thin amorphous Si (a-Si) films deposited on SiO{sub 2}/Si substrates in vacuum. Dependences of density and diameter of the Si nanodots on the a-Si film thickness and, annealing temperature and time were investigated by scanning electron microscopy. It is found that drastic increase (decrease) in the density (diameter) occurred at an a-Si thickness of 1 nm. By agglomeration of sub-nanometer thick a-Si films, a density larger than 10{sup 12} cm{sup -2}, an average diameter smaller than 5 nm, and a dispersion of diameter less than 15% were achieved.

  18. In situ growth of SiC nanowires on RS-SiC substrate(s)

    Science.gov (United States)

    Yang, Wen; Araki, Hiroshi; Hu, Quanli; Ishikawa, Nobuhiro; Suzuki, Hiroshi; Noda, Tetsuji

    2004-03-01

    SiC nanowires over 10 μm in length and 20-100 nm in diameter have been synthesized by a novel in situ chemical vapor growth process on RS-SiC plates. The SiC nanowires were identified as single crystal β-SiC with Si-C chemistry. The growth direction of the nanowires is . The growth mechanism is discussed and a kinetic vapor-solid growth mechanism is proposed. The process demonstrates the possibility to fabricate SiC nanowires in ceramic matrix composites, such as continuous SiC fibers reinforced SiC matrix composites, with the SiC nanowires uniformly dispersed in the matrix.

  19. Formation of nanocrystalline CrSi 2 layers in Si by ion implantation and pulsed annealing

    Science.gov (United States)

    Batalov, R. I.; Bayazitov, R. M.; Valeev, V. F.; Galkin, N. G.; Goroshko, D. L.; Galkin, K. N.; Chusovitin, E. A.; Gaiduk, P. I.; Ivlev, G. D.; Gatskevich, E. I.

    In this work buried nanocrystalline CrSi2 layers were synthesized by ion implantation, pulsed annealing and MBE. The structural, optical and thermoelectrical properties of CrSi2 layers were studied by methods of SEM, TEM, RBS, PL and Seebeck coefficient measurements. The characteristic features of pulsed nanosecond annealing of Cr-implanted Si and epitaxial growth of triple Si/nc-CrSi2/Si heterostructures were established. It is shown that grown Si/nc-CrSi2/Si heterostructures, which preliminary implanted with the high-dose (ϕ = 6 × 1016cm-2) of Cr+ ions, have the noticeable low temperature (T = 10 - 100 K) photoluminescence signal at 1450-1600 nm and the large Seebeck coefficient (-(60-300) μV/K) in the temperature range of T = 340 - 415 K.

  20. Heteroepitaxial growth of SiC on Si by gas source MBE with silacyclobutane

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.; Steckl, A.J. [Cincinnati Univ., OH (United States). Nanoelectronics Lab.; Loboda, M.J. [Dow Corning Corp., Midland, MI (United States)

    1998-06-01

    3C-SiC films have been grown by MBE on Si(100) and Si(111) from the organosilane precursor silacyclobutane at temperatures of 800 to 1000 C and pressures of 1 to 5 x 10{sup -6} Torr. The chemical composition of the grown films provided by SIMS indicates a Si to C atomic ratio of about 1. The chemical structure of SiC was confirmed by FTIR. The surface morphology and crystallinity of SiC films were studied by SEM and RHEED. X-ray diffraction reveals that SiC films grown on Si(111) with the presence of native oxide exhibit better crystallinity than those grown on Si(111) surfaces from which the oxide is removed in-situ prior to growth. (orig.) 11 refs.

  1. Si doping superlattice structure on 6H-SiC(0001

    Directory of Open Access Journals (Sweden)

    Li Lianbi

    2017-01-01

    Full Text Available Si-DSL structures multilayers are prepared on 6H-SiC(0001 successfully. The energy offsets of the n-Si/n-6H-SiC heterojunction in the conduction band and valance band are 0.21eV and 1.65eV, respectively. TEM characterizations of the p/n-Si DSL confirms the epitaxial growth of the Si films with [1-11] preferred orientation and the misfit dislocations with a Burgers vector of 1/3 at the p-Si/n-Si interface. J-V measurements indicate that the heterostructure has apparent rectifying behavior. Under visible illumination with light intensity of 0.6W/cm2, the heterostructure demonstrates significant photoelectric response, and the photocurrent density is 2.1mA/cm2. Non-UV operation of the SiC-based photoelectric device is realized.

  2. High-performance a -Si/c-Si heterojunction photoelectrodes for photoelectrochemical oxygen and hydrogen evolution

    KAUST Repository

    Wang, Hsin Ping

    2015-05-13

    Amorphous Si (a-Si)/crystalline Si (c-Si) heterojunction (SiHJ) can serve as highly efficient and robust photoelectrodes for solar fuel generation. Low carrier recombination in the photoelectrodes leads to high photocurrents and photovoltages. The SiHJ was designed and fabricated into both photoanode and photocathode with high oxygen and hydrogen evolution efficiency, respectively, by simply coating of a thin layer of catalytic materials. The SiHJ photoanode with sol-gel NiOx as the catalyst shows a current density of 21.48 mA/cm2 at the equilibrium water oxidation potential. The SiHJ photocathode with 2 nm sputter-coated Pt catalyst displays excellent hydrogen evolution performance with an onset potential of 0.640 V and a solar to hydrogen conversion efficiency of 13.26%, which is the highest ever reported for Si-based photocathodes. © 2015 American Chemical Society.

  3. Propagation of misfit dislocations from buffer/Si interface into Si

    Science.gov (United States)

    Liliental-Weber, Zuzanna [El Sobrante, CA; Maltez, Rogerio Luis [Porto Alegre, BR; Morkoc, Hadis [Richmond, VA; Xie, Jinqiao [Raleigh, VA

    2011-08-30

    Misfit dislocations are redirected from the buffer/Si interface and propagated to the Si substrate due to the formation of bubbles in the substrate. The buffer layer growth process is generally a thermal process that also accomplishes annealing of the Si substrate so that bubbles of the implanted ion species are formed in the Si at an appropriate distance from the buffer/Si interface so that the bubbles will not migrate to the Si surface during annealing, but are close enough to the interface so that a strain field around the bubbles will be sensed by dislocations at the buffer/Si interface and dislocations are attracted by the strain field caused by the bubbles and move into the Si substrate instead of into the buffer epi-layer. Fabrication of improved integrated devices based on GaN and Si, such as continuous wave (CW) lasers and light emitting diodes, at reduced cost is thereby enabled.

  4. Grafted SiC nanocrystals

    DEFF Research Database (Denmark)

    Saini, Isha; Sharma, Annu; Dhiman, Rajnish

    2017-01-01

    ), raman spectroscopy and X-ray diffraction (XRD) measurements. UV–Visible absorption spectroscopy was used to study optical properties such as optical energy gap (Eg), Urbach's energy (Eu), refractive index (n), real (ε1) and imaginary (ε2) parts of dielectric constant of PVA as well as PVA......) were determined. Microhardness measurements performed at an applied load of 9.8 mN showed an increase in the Knoop microhardness number (KHN) of PVA containing 0.015 wt% PVA-g-SiC nanocrystals. Detailed analysis of current-voltage data indicates that the conduction mechanism responsible for increase...

  5. Si@SiOx/Graphene Nanosheets Composite: Ball Milling Synthesis and Enhanced Lithium Storage Performance

    Directory of Open Access Journals (Sweden)

    Xiaoyong Tie

    2018-01-01

    Full Text Available Si@SiOx/grapheme nanosheet (Si@SiOx/GNS nanocomposites as high-performance anode materials for lithium-ion batteries are prepared by mechanically blending the mixture of expanded graphite (EG with Si nanoparticles, and characterized by Raman spectrum, X-ray diffraction (XRD, field emission scanning electron microscopy, and transmission electron microscopy. During ball milling process, the size of Si nanoparticles will decrease, and the layer of EG can be peeled off to thin multilayers. Electrochemical tests reveal that the Si@SiOx/GNS nanocomposites show enhanced cycling stability, high reversible capacity, and rate capability, even with high content of active materials of 80% and without electrolyte additives. The retained revisable capacity is 1,055 mAh g−1 after 50 cycles at 0.2 A g−1 and about 63.6% of the initial value. The great electrochemical performance of Si@SiOx/GNS nanocomposites can be ascribed to GNS prepared through heat-treat and ball-milling methods, the decrease in the size of Si nanoparticles and SiOx layer on Si surface, which enhance the interactions between Si and GNS.

  6. Microwave Annealing for NiSiGe Schottky Junction on SiGe P-Channel

    Directory of Open Access Journals (Sweden)

    Yu-Hsien Lin

    2015-11-01

    Full Text Available In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si0.57Ge0.43/Si through microwave annealing (MWA ranging from 200 to 470 °C for 150 s in N2 ambient. MWA has the advantage of being diffusion-less during activation, having a low-temperature process, have a lower junction leakage current, and having low sheet resistance (Rs and contact resistivity. In our study, a 20 nm NiSiGe Schottky junction was formed by TEM and XRD analysis at MWA 390 °C. The NiSiGe/n-Si Schottky junction exhibits the highest forward/reverse current (ION/IOFF ratio of ~3 × 105. The low temperature MWA is a very promising thermal process technology for NiSiGe Schottky junction manufacturing.

  7. Architecture et typologie des dolmens des confins du Gard et de l'Ardèche : à l'ouest d'Orgnac-l'Aven

    OpenAIRE

    Chateauneuf, Florent

    2009-01-01

    Depuis les travaux pionniers de la fin du XIXe siècle, l'étude des sépultures et des pratiques funéraires a été au coeur des recherches sur le Néolithique en France. Il sera question dans ce travail d'architecture mégalithique et plus précisément d'architecture funéraire dans un contexte d'inhumations collectives. Une infime partie des sites répertoriés a réellement fait l'objet d'une datation, cependant il est admis que la construction des dolmens des régions calcaires du Sud de la France se...

  8. Switching Performance Evaluation of Commercial SiC Power Devices (SiC JFET and SiC MOSFET) in Relation to the Gate Driver Complexity

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    and JFETs. The recent introduction of SiC MOSFET has proved that it is possible to have highly performing SiC devices with a minimum gate driver complexity; this made SiC power devices even more attractive despite their device cost. This paper presents an analysis based on experimental results...... of the switching losses of various commercially available Si and SiC power devices rated at 1200 V (Si IGBTs, SiC JFETs and SiC MOSFETs). The comparison evaluates the reduction of the switching losses which is achievable with the introduction of SiC power devices; this includes analysis and considerations...

  9. SI PC104 Performance Test Report

    Energy Technology Data Exchange (ETDEWEB)

    Montelongo, S

    2005-12-16

    The Spectral Instruments (SI) PC104 systems associated with the SI-1000 CCD camera exhibited intermittent power problems during setup, test and operations which called for further evaluation and testing. The SI PC104 System is the interface between the SI-1000 CCD camera and its associated Diagnostic Controller (DC). As such, the SI PC104 must be a reliable, robust system capable of providing consistent performance in various configurations and operating conditions. This SI PC104 system consists of a stackable set of modules designed to meet the PC104+ Industry Standard. The SI PC104 System consists of a CPU module, SI Camera card, Media converter card, Video card and a I/O module. The root cause of power problems was identified as failing solder joints at the LEMO power connector attached to the SI Camera Card. The recommended solution was to provide power to the PC104 system via a PC104+ power supply module configured into the PC104 stack instead of thru the LEMO power connector. Test plans (2) were developed to test SI PC104 performance and identify any outstanding issues noted during extended operations. Test Plan 1 included performance and image acquisition tests. Test Plan 2 verified performance after implementing recommendations. Test Plan 2 also included verifying integrity of system files and driver installation after bootup. Each test plan was implemented to fully test against each set of problems noted. Test Plan presentations and Test Plan results are attached as appendices. Anticipated test results will show successful operation and reliable performance of the SI PC104 system receiving its power via a PC104 power supply module. A SI PC104 Usage Recommendation Memo will be sent out to the SI PC104 User Community. Recommendation memo(s) are attached as appendices.

  10. Effect of SiC particle addition on microstructure of Mg2Si/Al composite

    Directory of Open Access Journals (Sweden)

    Zhao Yuguang

    2014-03-01

    Full Text Available In the present study, by adding SiC particles into Al-Si-Mg melt, Mg2Si and SiC particles hybrid reinforced Al matrix composites were fabricated through the Mg2Si in situ synthesis in melt combined with the SiC ex situ stir casting. The as-cast microstructure containing primary Mg2Si and SiC particles that distribute homogenously in Al matrix was successfully achieved. The effects of SiC particle addition on the microstructure of Mg2Si/Al composites were investigated by using scanning electron microscopy (SEM and XRD. The results show that, with increasing the fraction of the SiC particles from 5wt.% to 10wt.%, the morphologies of the primary Mg2Si particulates in the prepared samples remain polygonal, but the size of the primary phase decreases slightly. However, when the SiC particle addition reaches 15wt.%, the morphologies of the primary Mg2Si particulates change partially from polygonal to quadrangular with a decrease in size from 50 μm to 30 μm. The size of primary Al dendrites decreases with increasing fraction of the SiC particles from 0wt.% to 15wt.%. The morphology of the eutectic Mg2Si phase changes from a fiber-form to a short fiber-form and/or a dot-like shape with increasing fraction of the SiC particles. Furthermore, no significant change in dendrite arm spacing (DAS was observed in the presence of SiC particles.

  11. Influence of substrate treatment on the growth of advanced core–shell alloys and compounds of FeSi@SiO2 and SiO2 nanowires

    CSIR Research Space (South Africa)

    Thabethe, S

    2014-12-01

    Full Text Available Advanced core–shell FeSi@SiO(subx) nanowires are observed when FeCl(sub3) vapour is made to flow over a SiO(sub2)/Si substrate at 1100 degress C. The thickness of the SiO(subx) sheath (d0) is found to depend inversely as the period of time of HF...

  12. An optically controlled SiC lateral power transistor based on SiC/SiCGe super junction structure

    Energy Technology Data Exchange (ETDEWEB)

    Pu Hongbin; Cao Lin; Ren Jie; Chen Zhiming; Nan Yagong, E-mail: puhongbin@xaut.edu.c [Xi' an University of Technology, Xi' an 710048 (China)

    2010-04-15

    An optically controlled SiC/SiCGe lateral power transistor based on superjunction structure has been proposed, in which n-SiCGe/p-SiC superjunction structure is employed to improve device figure of merit. Performance of the novel optically controlled power transistor was simulated using Silvaco Atlas tools, which has shown that the device has a very good response to the visible light and the near infrared light. The optoelectronic responsivities of the device at 0.5 {mu}m and 0.7 {mu}m are 330 mA/W and 76.2 mA/W at 2 V based voltage, respectively. (semiconductor devices)

  13. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    OpenAIRE

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-01-01

    Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondar...

  14. Temperature depopulation of the GeSi/Si quantum dots with non-equilibrium charge carriers

    Science.gov (United States)

    Sofronov, A. N.; Vorobjev, L. E.; Firsov, D. A.; Balagula, R. M.; Tonkikh, A. A.

    2017-07-01

    We study the temperature dependencies of equilibrium and photo-induced infrared absorption in GeSi/Si quantum dots in a wide spectral range. We show that, in spite of the large valence band offset at GeSi/Si interface and strong confinement for holes, the effect of intensive temperature depopulation of the GeSi/Si quantum dots can take place even at the temperatures below 300 K due to the large difference in density of states of the silicon valence band and quantum dot states, when the bipolar diffusion of charge carriers is not restricted.

  15. Catalyzed precipitation in Al-Cu-Si

    Science.gov (United States)

    Mitlin, D.; Morris, J. W.; Radmilovic, V.

    2000-11-01

    The work reported here concerns the effect of Si on the precipitation of θ' phase (metastable Al2Cu) during the isothermal aging of Al-2Cu-1 Si (wt pct). The binary alloys Al-2Cu and Al-1 Si were studied for comparison. Only two precipitate phases were detected: essentially pure Si in Al-1 Si and Al-2Cu-1 Si, and θ' (metastable Al2Cu) in Al-2Cu and Al-2Cu-1Si. On aging the ternary alloy at 225 °C, Si precipitates first and catalyzes the θ' phase. The precipitates in the ternary alloy are smaller, are more densely distributed, have lower aspect ratios, and coarsen more slowly than those in the binary Al-2Cu aged at the same temperature. While the shapes of individual θ' precipitates in binary Al-2Cu are strongly affected by the kinetic problem of nucleating growth ledges, which produces a significant scatter in the aspect ratio for samples of given thickness, the overall evolution of particle shape with size follows the predictions of the Khachaturyan-Hairapetyan (KH) thermoelastic theory, which reduces to κ= L/d ∞ √ L at large sizes. The KH theory provides an estimate for the interfacial tension of the broad Al- θ' interface of 85 to 96 mJ/m2, which is near the values for other low-energy interfaces in Al, such as the twin boundary energy (100 mJ/m2) and the antiphase boundary energy in δ' Al3Li (70 mJ/m2). Si and θ' precipitates in Al-2Cu-1 Si have a strong elastic interaction because of their compensating strain fields. This elastic interaction promotes the nucleation of θ' precipitates on Si, decreases the expected aspect ratio of θ', and inhibits coarsening. Finally, Si precipitation in ternary Al-2Cu-1 Si differs from that in binary Al-1 Si in that the Si precipitates are coarser, more equiaxed, and more extensively twinned. These changes appear to be effects of Cu, which increases the solubility of Si in Al and adsorbs on the Si-Al interface, promoting twinning by a “step-poisoning” effect at the interface.

  16. Epitaxy of Si1- x C x via ultrahigh-vacuum chemical vapor deposition using Si2H6, Si3H8, or Si4H10 as Si precursors

    Science.gov (United States)

    Koo, Sangmo; Jang, Hyunchul; Ko, Dae-Hong

    2017-09-01

    In this study, disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H10) were used as Si precursors for the growth of Si1- x C x epilayers, and the growth properties of the layers were compared. The use of a higher-order silane significantly increased the growth rates of the Si1- x C x epilayers at a processing temperature of 650 °C. In addition, a higher growth rate realized by using a higher-order silane promoted an increase in the substitutional carbon concentration in the Si1- x C x epilayers owing to the additional injection of a C-source gas (SiH3CH3) and the incorporation of C atoms into substitutional sites. The differences in growth properties between Si precursors were explained on the basis of reaction mechanisms.

  17. Optical Properties Of Sputtered Si: H

    Science.gov (United States)

    Martin, P. M.; Pawlewicz, W. T.; Mann, I. B.

    1982-04-01

    Sputtered Si:H is a very promising material for use in thin-film solar cells, solar selective absorbers and optical coatings for the near infrared region. Optical property-composition relationships have been determined for Si:H coatings having wide ranges of H content and Si-H bonding. The dependence of the optical absorption edge, optical band gap and refractive index at 2 μm wavelength on H content and Si-H bonding is described. Microstructural and topographical features of the films that influence their absorption and scattering characteristics are discussed. Composition and bonding diagrams used to select deposition conditions for the desired optical properties are also presented. Finally, multilayer Si:H/Si02 all-dielectric laser mirrors with reflectances greater than 99% at 1.315, 2.7 and 3.8 μm are described to illustrate the application of these coatings.

  18. Synthesis of biomorphaus SiC-ceramics

    Directory of Open Access Journals (Sweden)

    Egelja Adela D.

    2007-01-01

    Full Text Available The carbothermal reduction processing of partially mineralized fir (Abies alba samples was used to obtain highly-porous SiC ceramics with cellular structure. The infiltration of TEOS (tetraetilortosilikat, Si(OC2H54 as a silica source, was conducted in order to carry out the mineralization process. Synthesis of the SiC was achieved with a C/SiO2 replica annealing at 1723 K in Ar atmosphere. The obtained samples were characterized using X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM and energy dispersive spectrometry (EDS. The experimental results revealed that the hierarchical bimorphous wood structure was preserved even after high-temperature treatment. Microstructural characterization of the ceramics revealed the presence of the P-SiC phase and traces of the a-SiC phase.

  19. On the role of heterolayer relaxation in luminescence response of Si/SiGe:Er structures

    Energy Technology Data Exchange (ETDEWEB)

    Krasilnikova, Ludmila; Stepikhova, Margarita; Drozdov, Yurij; Krasilnik, Zakharii [Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation); Chalkov, Vadim; Shengurov, Vladimir [Physico-Technical Research Institute, Nizhny Novgorod State University, Gagarin Ave. 23, 603950 Nizhny Novgorod (Russian Federation)

    2011-03-15

    In this contribution we discuss the luminescence properties of Si/Si{sub 1-x}Ge{sub x}:Er/Si structures being of interest for a laser realization. The influence of the strain relaxation processes that take place in such kind of structures on their photoluminescence response at 1.54 {mu}m has been analyzed. The studies were performed for Si/Si{sub 1-x}Ge{sub x}:Er/Si structures with the different thickness of Si{sub 1-x}Ge{sub x}:Er layers, and consequently the degree of strain relaxation. It is shown that the structural defects arising in Si/Si{sub 1-x}Ge{sub x}:Er/Si structures due to the relaxation play only negligible role in their photoluminescence response. The contribution of the structural defects in the photoluminescence response at 1.54 {mu}m became apparent only in thin partially relaxed Si/Si{sub 1-x}Ge{sub x}:Er/Si structures, the photoluminescence spectra of which are represented by the broad ''defect related'' lines. Intense photoluminescence related with the optically active Er centers of different types was observed for the strained and completely relaxed Si/Si{sub 1-x}Ge{sub x}:Er/Si structures containing thick (d > 1 {mu}m) Si{sub 1-x}Ge{sub x}:Er layers. The external quantum efficiency of these structures reaches the value of 6.3 x 10{sup -5} at T =77 K. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. The compatibility of SiC/SiC composites with ceramic breeder materials

    Energy Technology Data Exchange (ETDEWEB)

    Sample, T. (Institute for Advanced Materials, Commission of the European Communities, Joint Research Centre, I-21020, Ispra (Vatican City State, Holy See) (Italy)); Fenici, P. (Institute for Advanced Materials, Commission of the European Communities, Joint Research Centre, I-21020, Ispra (Vatican City State, Holy See) (Italy)); Kolbe, H. (Institute for Advanced Materials, Commission of the European Communities, Joint Research Centre, I-21020, Ispra (Vatican City State, Holy See) (Italy)); Orecchia, L. (Institute for Advanced Materials, Commission of the European Communities, Joint Research Centre, I-21020, Ispra (Vatican City State, Holy See) (Italy))

    1994-09-01

    The compatibility of three lithium-containing ceramic breeder materials Li[sub 4]SiO[sub 4], Li[sub 2]ZrO[sub 3] and LiAlO[sub 2] with two industrially available SiC/SiC composites was determined. Simple capsule tests were carried out at 600 and 800 C in closed capsules, dynamic vacuum and flowing helium. All three breeder materials were reactive towards the SiO[sub 2] content of the SiC/SiC composites forming a surface layer of Li[sub 2]SiO[sub 3]. The as-received' Li[sub 4]SiO[sub 4] was found to be much more reactive than Li[sub 2]ZrO[sub 3] or LiAlO[sub 2]. However, the greater reactivity was found to be governed by the Li[sub 2]CO[sub 3] impurity content of the Li[sub 4]SiO[sub 4] granules. Removal of the Li[sub 2]CO[sub 3], through thermal decomposition under vacuum, reduced the extend of Li[sub 2]SiO[sub 3] formation. The reaction of the breeder materials to form Li[sub 2]SiO[sub 3] is briefly discussed in relation to the probable operating conditions for a SiC/SiC composite structural material in a blanket. ((orig.))

  1. Photoelectric Properties of Si Doping Superlattice Structure on 6H-SiC(0001).

    Science.gov (United States)

    Li, Lianbi; Zang, Yuan; Hu, Jichao; Lin, Shenghuang; Chen, Zhiming

    2017-05-25

    The energy-band structure and visible photoelectric properties of a p/n-Si doping superlattice structure (DSL) on 6H-SiC were simulated by Silvaco-TCAD. The,n the Si-DSL structures with 40 nm-p-Si/50 nm-n-Si multilayers were successfully prepared on 6H-SiC(0001) Si-face by chemical vapor deposition. TEM characterizations of the p/n-Si DSL confirmed the epitaxial growth of the Si films with preferred orientation and the misfit dislocations with a Burgers vector of 1/3 at the p-Si/n-Si interface. The device had an obvious rectifying behavior, and the turn-on voltage was about 1.2 V. Under the visible illumination of 0.6 W/cm², the device demonstrated a significant photoelectric response with a photocurrent density of 2.1 mA/cm². Visible light operation of the Si-DSL/6H-SiC heterostructure was realized for the first time.

  2. Photoelectric Properties of Si Doping Superlattice Structure on 6H-SiC(0001

    Directory of Open Access Journals (Sweden)

    Lianbi Li

    2017-05-01

    Full Text Available The energy-band structure and visible photoelectric properties of a p/n-Si doping superlattice structure (DSL on 6H-SiC were simulated by Silvaco-TCAD. The,n the Si-DSL structures with 40 nm-p-Si/50 nm-n-Si multilayers were successfully prepared on 6H-SiC(0001 Si-face by chemical vapor deposition. TEM characterizations of the p/n-Si DSL confirmed the epitaxial growth of the Si films with preferred orientation and the misfit dislocations with a Burgers vector of 1/3 <21-1> at the p-Si/n-Si interface. The device had an obvious rectifying behavior, and the turn-on voltage was about 1.2 V. Under the visible illumination of 0.6 W/cm2, the device demonstrated a significant photoelectric response with a photocurrent density of 2.1 mA/cm2. Visible light operation of the Si-DSL/6H-SiC heterostructure was realized for the first time.

  3. Microstructure design and control for improvement of thermal conductivity of SiCf/SiC composites

    Science.gov (United States)

    Yoshida, Katsumi; Kajikawa, Satoshi; Yano, Toyohiko

    2013-09-01

    We focused on microstructure design and control of SiCf/SiC composite based on our fabrication process and the simple model of thermal conductivity of the SiCf/SiC composite, and the improvement of their thermal conductivity was investigated. Submicron-sized α-SiC with coarse α-SiC particles addition was used as the starting materials for SiC matrix layers between SiC fiber cloths because it showed higher thermal conductivity. The thermal conductivity of PCS-composite, EPD-composite and Untreated-composite was 18, 45 and 56 W/m K, respectively, and these values were much higher than that of the composites reported in our previous papers. Untreated composite is simply considered as a multilayered composite consisting of the SiC fiber layers with high thermal conductivity and the SiC matrix layers with high thermal conductivity. The experimental thermal conductivity of the Untreated composite well agreed with the theoretical thermal conductivity calculated by series model. Thermal conductivity of EPD-composite was lower than that of Untreated composite. In EPD-composite, the thermal conductivity of SiC fiber layers with the SiC matrix should be lower than that of SiC fibers themselves due to the SiC matrix with slightly lower thermal conductivity in SiC fiber cloths. The SiC matrix formed in SiC fiber cloths in PCS-composite was derived from PCS, and this matrix would show much lower thermal conductivity due to its low crystallinity. PCS-composite is considered as a multilayered composite consisting of the SiC fiber layers with very low thermal conductivity and the SiC matrix layers with high thermal conductivity, and thus the PCS-composite has low thermal conductivity. In this study, higher thermal conductivity of SiCf/SiC composite was successfully achieved by EPD process and using microstructure-controlled SiC matrix and polycrystalline SiC fibers.

  4. Chemical compatibility issues associated with use of SiC/SiC in advanced reactor concepts

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Dane F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-09-01

    Silicon carbide/silicon carbide (SiC/SiC) composites are of interest for components that will experience high radiation fields in the High Temperature Gas Cooled Reactor (HTGR), the Very High Temperature Reactor (VHTR), the Sodium Fast Reactor (SFR), or the Fluoride-cooled High-temperature Reactor (FHR). In all of the reactor systems considered, reactions of SiC/SiC composites with the constituents of the coolant determine suitability of materials of construction. The material of interest is nuclear grade SiC/SiC composites, which consist of a SiC matrix [high-purity, chemical vapor deposition (CVD) SiC or liquid phase-sintered SiC that is crystalline beta-phase SiC containing small amounts of alumina-yttria impurity], a pyrolytic carbon interphase, and somewhat impure yet crystalline beta-phase SiC fibers. The interphase and fiber components may or may not be exposed, at least initially, to the reactor coolant. The chemical compatibility of SiC/SiC composites in the three reactor environments is highly dependent on thermodynamic stability with the pure coolant, and on reactions with impurities present in the environment including any ingress of oxygen and moisture. In general, there is a dearth of information on the performance of SiC in these environments. While there is little to no excess Si present in the new SiC/SiC composites, the reaction of Si with O2 cannot be ignored, especially for the FHR, in which environment the product, SiO2, can be readily removed by the fluoride salt. In all systems, reaction of the carbon interphase layer with oxygen is possible especially under abnormal conditions such as loss of coolant (resulting in increased temperature), and air and/ or steam ingress. A global outline of an approach to resolving SiC/SiC chemical compatibility concerns with the environments of the three reactors is presented along with ideas to quickly determine the baseline compatibility performance of SiC/SiC.

  5. Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

    Science.gov (United States)

    Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

    2017-11-25

    The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

  6. Dopo il Grande Evento: politiche “utili” per la mobilità Beyond the Mega Events: “Useful” Policies for Urban Mobility

    Directory of Open Access Journals (Sweden)

    Andrea Ceudech

    2008-08-01

    Full Text Available Il contributo indaga i limiti delle politiche urbane e in particolare di quelle sulla mobilità attuate per i Grandi Eventi, evidenziando in molti casi la tendenza a privilegiare la realizzazione di infrastrutture, più che politiche sui servizi, la cui reale utilità è spesso messa in dubbio dalla pratica e i cui costi manutentivi divengono spesso nuovi carichi per la collettività. Sulla base di una breve rassegna delle politiche sulla mobilità maggiormente implementate nella preparazione e gestione dei Grandi Eventi, il contributo evidenzia in maniera critica punti di forza e punti di debolezza delle esperienze analizzate in riferimento sia alla gestione del grande evento, sia in riferimento alla loro reale utilità per la collettività dopo che il grande evento è terminato. Nell’ultima parte del contributo si evidenziano i principali requisiti che le politiche sulla mobilità devono possedere affinché apportino reali vantaggi alla città anche una volta che il Grande Evento è terminato.The paper analyses, through different examples, the limits of the urban mobility policies implemented for mega events, highlighting the tendency to privilege the infrastructure realization, more than policies on services, whose real usefulness is often put in doubt from the practice and whose maintenance often become a new cost for the community. On the base of a short review of the mobility policies mainly implemented in the preparation and management of the mega events, the paper highlights, from a critical point of view, the strengths and weaknesses of some experiences with reference to the real usefulness of urban mobility for the community beyond the mega event. The outcomes and the so-called “legacy” of the mega events for the cities are very different. Mega sport events, like the Olympic Games, have often involved only the realization of works for the event while events like the International Expositions have determined the acquisition of

  7. Graphene/Si-nanowire heterostructure molecular sensors.

    Science.gov (United States)

    Kim, Jungkil; Oh, Si Duk; Kim, Ju Hwan; Shin, Dong Hee; Kim, Sung; Choi, Suk-Ho

    2014-06-20

    Wafer-scale graphene/Si-nanowire (Si-NW) array heterostructures for molecular sensing have been fabricated by vertically contacting single-layer graphene with high-density Si NWs. Graphene is grown in large scale by chemical vapour deposition and Si NWs are vertically aligned by metal-assisted chemical etching of Si wafer. Graphene plays a key role in preventing tips of vertical Si NWs from being bundled, thereby making Si NWs stand on Si wafer separately from each other under graphene, a critical structural feature for the uniform Schottky-type junction between Si NWs and graphene. The molecular sensors respond very sensitively to gas molecules by showing 37 and 1280% resistance changes within 3.5/0.15 and 12/0.15 s response/recovery times under O2 and H2 exposures in air, respectively, highest performances ever reported. These results together with the sensor responses in vacuum are discussed based on the surface-transfer doping mechanism.

  8. siRNA and innate immunity.

    Science.gov (United States)

    Robbins, Marjorie; Judge, Adam; MacLachlan, Ian

    2009-06-01

    Canonical small interfering RNA (siRNA) duplexes are potent activators of the mammalian innate immune system. The induction of innate immunity by siRNA is dependent on siRNA structure and sequence, method of delivery, and cell type. Synthetic siRNA in delivery vehicles that facilitate cellular uptake can induce high levels of inflammatory cytokines and interferons after systemic administration in mammals and in primary human blood cell cultures. This activation is predominantly mediated by immune cells, normally via a Toll-like receptor (TLR) pathway. The siRNA sequence dependency of these pathways varies with the type and location of the TLR involved. Alternatively nonimmune cell activation may also occur, typically resulting from siRNA interaction with cytoplasmic RNA sensors such as RIG1. As immune activation by siRNA-based drugs represents an undesirable side effect due to the considerable toxicities associated with excessive cytokine release in humans, understanding and abrogating this activity will be a critical component in the development of safe and effective therapeutics. This review describes the intracellular mechanisms of innate immune activation by siRNA, the design of appropriate sequences and chemical modification approaches, and suitable experimental methods for studying their effects, with a view toward reducing siRNA-mediated off-target effects.

  9. Ge/SiGe for silicon photonics

    Science.gov (United States)

    Ishikawa, Yasuhiko

    2017-01-01

    Near-infrared Ge photonic devices on a Si platform are presented toward low-cost, low-energy and high-capacity optical communications. Using Ge epitaxial layers selectively grown by chemical vapor deposition on Si-on-insulator layers, Ge photodiodes (PDs) of vertical pin structures are integrated with Si optical waveguides. The integrated Ge PDs show high responsivities as large as 0.8 A/W at 1.55 μm with the 3-dB cutoff frequency more than 10 GHz. SiGe/Ge heterostructures have potential applications to higher-performance devices. One application is to low-noise and low-voltage avalanche photodiodes (APDs), where a SiGe layer is inserted at the interface between the optical absorption layer of Ge and the carrier-multiplication layer of Si or Ge. The band discontinuity at the interface enhances the impact ionization for photo-generated carriers injected via SiGe. Fabricated APDs show an enhanced multiplication gain. The other application of SiGe is to a stressor to control the direct bandgap of Ge. As a proof of concept, a tensile-strained Si0.2Ge0.8 overlayer is shown to induce a compressive stress in the underlying Ge mesa stripe, leading to a blue shift in the absorption edge of Ge.

  10. Si isotope homogeneity of the solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Pringle, Emily A.; Savage, Paul S.; Moynier, Frédéric [Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 (United States); Jackson, Matthew G. [Department of Earth Science, University of California, Santa Barbara, CA 93109 (United States); Barrat, Jean-Alix, E-mail: eapringle@wustl.edu, E-mail: savage@levee.wustl.edu, E-mail: pringle@ipgp.fr, E-mail: moynier@ipgp.fr, E-mail: jackson@geol.ucsb.edu, E-mail: Jean-Alix.Barrat@univ-brest.fr [Université Européenne de Bretagne, Université de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, F-29280 Plouzané Cedex (France)

    2013-12-20

    The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in {sup 29}Si/{sup 28}Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of {sup 29}Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.

  11. SiD Letter of Intent

    Energy Technology Data Exchange (ETDEWEB)

    Aihara, H., (Ed.); Burrows, P., (Ed.); Oreglia, M., (Ed.); Berger, E.L.; Guarino, V.; Repond, J.; Weerts, H.; Xia, L.; Zhang, J.; /Argonne, HEP; Zhang, Q.; /Argonne, HEP /Beijing, Inst. High Energy Phys.; Srivastava, A.; /Birla Inst. Tech. Sci.; Butler, J.M.; /Boston U.; Goldstein, Joel; Velthuis, J.; /Bristol U.; Radeka, V.; /Brookhaven; Zhu, R.-Y.; /Caltech.; Lutz, P.; /DAPNIA, Saclay; de Roeck, A.; Elsener, K.; Gaddi, A.; Gerwig, H.; /CERN /Cornell U., LNS /Ewha Women' s U., Seoul /Fermilab /Gent U. /Darmstadt, GSI /Imperial Coll., London /Barcelona, Inst. Microelectron. /KLTE-ATOMKI /Valencia U., IFIC /Cantabria Inst. of Phys. /Louis Pasteur U., Strasbourg I /Durham U., IPPP /Kansas State U. /Kyungpook Natl. U. /Annecy, LAPP /LLNL, Livermore /Louisiana Tech. U. /Paris U., VI-VII /Paris U., VI-VII /Munich, Max Planck Inst. /MIT, LNS /Chicago, CBC /Moscow State U. /Nanjing U. /Northern Illinois U. /Obninsk State Nucl. Eng. U. /Paris U., VI-VII /Strasbourg, IPHC /Prague, Inst. Phys. /Princeton U. /Purdue U. /Rutherford /SLAC /SUNY, Stony Brook /Barcelona U. /Bonn U. /UC, Davis /UC, Santa Cruz /Chicago U. /Colorado U. /Delhi U. /Hawaii U. /Helsinki U. /Indiana U. /Iowa U. /Massachusetts U., Amherst /Melbourne U. /Michigan U. /Minnesota U. /Mississippi U. /Montenegro U. /New Mexico U. /Notre Dame U. /Oregon U. /Oxford U. /Ramon Llull U., Barcelona /Rochester U. /Santiago de Compostela U., IGFAE /Hefei, CUST /Texas U., Arlington /Texas U., Dallas /Tokyo U. /Washington U., Seattle /Wisconsin U., Madison /Wayne State U. /Yale U. /Yonsei U.

    2012-04-11

    This document presents the current status of the Silicon Detector (SiD) effort to develop an optimized design for an experiment at the International Linear Collider. It presents detailed discussions of each of SiD's various subsystems, an overview of the full GEANT4 description of SiD, the status of newly developed tracking and calorimeter reconstruction algorithms, studies of subsystem performance based on these tools, results of physics benchmarking analyses, an estimate of the cost of the detector, and an assessment of the detector R and D needed to provide the technical basis for an optimised SiD.

  12. Strain relaxation in nano-patterned strained-Si/SiGe heterostructure on insulator

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xuyn, E-mail: liuyan@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Graduate University of Chinese Academy of Sciences, Beijing 100080 (China); Liu Weili, E-mail: rabbitlwl@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Ma Xiaobo [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Graduate University of Chinese Academy of Sciences, Beijing 100080 (China); Lv Shilong; Song Zhitang; Lin Chenglu [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China)

    2010-03-15

    In order to evaluate the strain stability, arrays of strained Si/SiGe nano-stripes and nano-pillars were fabricated by Electron-Beam Lithography (EBL) and Reactive-Ion Etching (RIE). The strain relaxation in the patterned strained Si on SiGe-on-insulator (SGOI) was investigated by high-resolution UV micro-Raman spectroscopy. The Raman measurements before and after patterning indicate that most of the strain in the top strained Si is maintained until scaling down to 300 nm, and relaxation of <15% is observed in pillars with a dimension of 150 nm x 150 nm. In the nano-patterned heterostructure strained Si/SiGe, the observed relaxation is small, which is mainly attributed to the fully relaxed and dislocation-free SiGe virtual substrate fabricated by modified Ge condensation.

  13. Al+Si Interface Optical Properties Obtained in the Si Solar Cell Configuration

    Energy Technology Data Exchange (ETDEWEB)

    Deceglie, Michael G [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Silverman, Timothy J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Subedi, Indra [University of Toledo; Podraza, Nikolas J. [University of Toledo

    2017-10-18

    Al is a commonly used material for rear side metallization in commercial silicon (Si) wafer solar cells. In this study, through-the-silicon spectroscopic ellipsometry is used in a test sample to measure Al+Si interface optical properties like those in Si wafer solar cells. Two different spectroscopic ellipsometers are used for measurement of Al+Si interface optical properties over the 1128-2500 nm wavelength range. For validation, the measured interface optical properties are used in a ray tracing simulation over the 300-2500 nm wavelength range for an encapsulated Si solar cell having random pyramidal texture. The ray tracing model matches well with the measured total reflectance at normal incidence of a commercially available Si module. The Al+Si optical properties presented here enable quantitative assessment of major irradiance/current flux losses arising from reflection and parasitic absorption in encapsulated Si solar cells.

  14. Low specific contact resistance of NiSi and PtSi to Si: impact of interface

    NARCIS (Netherlands)

    Tiggelman, N.; Kovalgin, Alexeij Y.; Brennan, R.; Wolters, Robertus A.M.

    2010-01-01

    We recently reported low specific contact resistance values of NiSi and PtSi to silicon. In recent publications, such low values were attributed to dopant segregation. In this work, we tested this hypothesis by spreading resistance probe and secondary ion mass spectroscopy analyses. The observed

  15. Sputtered Gold as an Effective Schottky Gate for Strained Si/SiGe Nanostructures

    Science.gov (United States)

    Scott, Gavin; Xiao, Ming; Croke, Ed; Yablonovitch, Eli; Jiang, Hongwen

    2007-03-01

    Metallization of Schottky surface gates by sputtering Au on strained Si/SiGe heterojunctions enables the depletion of the two dimensional electron gas (2DEG) at a relatively small voltage while maintaining an extremely low level of leakage current. A fabrication process has been developed to enable the formation of sub-micron Au electrodes sputtered onto Si/SiGe without the need of a wetting layer.

  16. Raman scattering in Si/SiGe nanostructures: Revealing chemical composition, strain, intermixing, and heat dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Mala, S. A.; Tsybeskov, L., E-mail: tsybesko@njit.edu [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102 (United States); Lockwood, D. J.; Wu, X.; Baribeau, J.-M. [National Research Council, Ottawa, Ontario K1A 0R6 (Canada)

    2014-07-07

    We present a quantitative analysis of Raman scattering in various Si/Si{sub 1-x}Ge{sub x} multilayered nanostructures with well-defined Ge composition (x) and layer thicknesses. Using Raman and transmission electron microscopy data, we discuss and model Si/SiGe intermixing and strain. By analyzing Stokes and anti-Stokes Raman signals, we calculate temperature and discuss heat dissipation in the samples under intense laser illumination.

  17. Passivation of surface-nanostructured f-SiC and porous SiC

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang; Ou, Yiyu

    The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper.......The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper....

  18. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  19. Addimer diffusions on Si(100)

    CERN Document Server

    Lee, G D; Lu, Z Y; Ho, K M

    1999-01-01

    The diffusion pathways along the trough and between the trough and the dimer row on the Si(100) surface are investigated by tight-binding molecular dynamics calculations using the environment dependent tight-binding silicon potential and by ab initio calculations using the Car-Parrinello method. The studies discover new diffusion pathways consisting of rotation of addimer. The calculated energy barrier are in excellent agreement with experiment. The rotational diffusion pathway between the trough and the dimer row is much more energetically favorable than other diffusion pathways by parallel and perpendicular addimer. The new pathway along the trough is nearly same as the energy barrier of the diffusion pathway by dissociation of the addimer.

  20. Definitive Mineralogical Analysis of Martian Rocks and Soil Using the CheMin XRD/XRF Instrument and the USDC Sampler

    Science.gov (United States)

    Blake, D. F.; Sarrazin, P.; Chipera, S. J.; Bish, D. L.; Vaniman, D. T.; Bar-Cohen, Y.; Sherrit, S.; Collins, S.; Boyer, B.; Bryson, C.

    2003-01-01

    The search for evidence of extant or extinct life on Mars will initially be a search for evidence of present or past conditions supportive of life (e.g., evidence of water), not for life itself. Definitive evidence of past or present water activity lies in the discovery of: * Hydrated minerals: The "rock type" hosting the hydrated minerals could be igneous, metamorphic, or sedimentary, with only a minor hydrated mineral phase. Therefore, the identification of minor phases is important. * Clastic sediments: Clastic sediments are commonly identified by the fact that they contain minerals of disparate origin that could only have come together as a mechanical mixture. Therefore, the identification of all minerals present in a mixture to ascertain mineralogical source regions is important. * Hydrothermal precipitates and chemical sediments: Some chemical precipitates are uniquely identified only by their structure. For example, Opal A, Opal CT, tridymite, crystobalite, high and low Quartz all have the same composition (SiO2) but different crystal structures indicative of different environments - from hydrothermal hydrothermal formation to low temperature precipitation. Other silica types such as stishovite can provide evidence of shock metamorphism. Therefore, identification of crystal structures and structural polymorphs is important. The elucidation of the nature of the Mars soil will require the identification of mineral components that can unravel its history and the history of the Mars atmosphere.

  1. Evaluation de la diversité bactérienne et de son évolution pendant la conservation de la viande fraîche bovine de différentes origines emballée sous vide

    OpenAIRE

    Didimo Imazaki, Pedro Henrique; Maréchal, Aline; Nezer, Carine; Taminiau, Bernard; Daube, Georges; Clinquart, Antoine

    2011-01-01

    Un grand nombre de bactéries lactiques associées à la viande sont connues comme d'importants producteurs de bactériocines. Ces bactériocines sont des toxines protéiques présentant une activité bactéricide ou bactériostatique contre des espèces proches de la souche productrice. La présence de certaines bactéries lactiques dans la viande fraîche pourrait donc prolonger la durée de conservation, et améliorer la stabilité microbienne et la sécurité de ce produit. Dans ce contexte, une étude a été...

  2. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    Unknown

    SiC ceramics. O P CHAKRABARTI*, P K DAS and S MONDAL. Central Glass and Ceramic Research Institute, Kolkata 700 032, India. Abstract. MoSi2–RBSC composite samples were prepared by infiltration of Si–2 at.% Mo melt into a preform of commercial SiC and petroleum coke powder. The infiltrated sample had a ...

  3. Advances in SiC/SiC Composites for Aero-Propulsion

    Science.gov (United States)

    DiCarlo, James A.

    2013-01-01

    In the last decade, considerable progress has been made in the development and application of ceramic matrix composites consisting of silicon carbide (SiC) based matrices reinforced by small-diameter continuous-length SiC-based fibers. For example, these SiC/SiC composites are now in the early stages of implementation into hot-section components of civil aero-propulsion gas turbine engines, where in comparison to current metallic components they offer multiple advantages due to their lighter weight and higher temperature structural capability. For current production-ready SiC/SiC, this temperature capability for long time structural applications is 1250 degC, which is better than 1100 degC for the best metallic superalloys. Foreseeing that even higher structural reliability and temperature capability would continue to increase the advantages of SiC/SiC composites, progress in recent years has also been made at NASA toward improving the properties of SiC/SiC composites by optimizing the various constituent materials and geometries within composite microstructures. The primary objective of this chapter is to detail this latter progress, both fundamentally and practically, with particular emphasis on recent advancements in the materials and processes for the fiber, fiber coating, fiber architecture, and matrix, and in the design methods for incorporating these constituents into SiC/SiC microstructures with improved thermo-structural performance.

  4. Microstructure and abrasive wear studies of laser clad Al-Si/SiC composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Colaco, R.; Ocelik, V.; De Hosson, J. Th. M.; Vilar, R.; Gyulai, J; Szabo, PJ

    2007-01-01

    Surface coatings of Al-Si/SiC metal-matrix composites were deposited on Al-7 wt. % Si alloy substrates by laser cladding. The microstructure of the coatings was characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microstructure of the coating

  5. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by ...

    Indian Academy of Sciences (India)

    Administrator

    in situ reaction synthesis of TiC/Si/Al powders. BAOYAN LIANG†, MINGZHI WANG*, ... The microstructure and mechanical properties of Ti3SiC2–SiC nanocomposite fabricated by in situ hot pressing (HP) synthesis process were .... 7 mm × 27 mm bars for measuring the three-point bend- ing strength with a span of 20 mm. 3.

  6. siRNAmod: A database of experimentally validated chemically modified siRNAs.

    Science.gov (United States)

    Dar, Showkat Ahmad; Thakur, Anamika; Qureshi, Abid; Kumar, Manoj

    2016-01-28

    Small interfering RNA (siRNA) technology has vast potential for functional genomics and development of therapeutics. However, it faces many obstacles predominantly instability of siRNAs due to nuclease digestion and subsequently biologically short half-life. Chemical modifications in siRNAs provide means to overcome these shortcomings and improve their stability and potency. Despite enormous utility bioinformatics resource of these chemically modified siRNAs (cm-siRNAs) is lacking. Therefore, we have developed siRNAmod, a specialized databank for chemically modified siRNAs. Currently, our repository contains a total of 4894 chemically modified-siRNA sequences, comprising 128 unique chemical modifications on different positions with various permutations and combinations. It incorporates important information on siRNA sequence, chemical modification, their number and respective position, structure, simplified molecular input line entry system canonical (SMILES), efficacy of modified siRNA, target gene, cell line, experimental methods, reference etc. It is developed and hosted using Linux Apache MySQL PHP (LAMP) software bundle. Standard user-friendly browse, search facility and analysis tools are also integrated. It would assist in understanding the effect of chemical modifications and further development of stable and efficacious siRNAs for research as well as therapeutics. siRNAmod is freely available at: http://crdd.osdd.net/servers/sirnamod.

  7. Thermal Stability of siRNA Modulates Aptamer- conjugated siRNA Inhibition

    Directory of Open Access Journals (Sweden)

    Alexey Berezhnoy

    2012-01-01

    Full Text Available Oligonucleotide aptamer-mediated in vivo cell targeting of small interfering RNAs (siRNAs is emerging as a useful approach to enhance the efficacy and reduce the adverse effects resulting from siRNA-mediated genetic interference. A current main impediment in aptamer-mediated siRNA targeting is that the activity of the siRNA is often compromised when conjugated to an aptamer, often requiring labor intensive and time consuming design and testing of multiple configurations to identify a conjugate in which the siRNA activity has not been significantly reduced. Here, we show that the thermal stability of the siRNA is an important parameter of siRNA activity in its conjugated form, and that siRNAs with lower melting temperature (Tm are not or are minimally affected when conjugated to the 3′ end of 2′F-pyrimidine-modified aptamers. In addition, the configuration of the aptamer-siRNA conjugate retains activity comparable with the free siRNA duplex when the passenger strand is co-transcribed with the aptamer and 3′ overhangs on the passenger strand are removed. The approach described in this paper significantly reduces the time and effort necessary to screening siRNA sequences that retain biological activity upon aptamer conjugation, facilitating the process of identifying candidate aptamer-siRNA conjugates suitable for in vivo testing.

  8. Polycrystalline SiC as source material for the growth of fluorescent SiC layers

    DEFF Research Database (Denmark)

    Kaiser, M.; Hupfer, T.; Jokubavicus, V.

    2013-01-01

    Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport m...

  9. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    The infiltrated sample had a density > 92% of the theoretical density (TD) and microstructurally contained SiC, MoSi2, residual Si and unreacted C. The material was tested for indentation fracture toughness at room temperature with a Vicker's indenter and KIC was found to be 4.42 MPa√m which is around 39% higher than ...

  10. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 34; Issue 7. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by in situ reaction synthesis of TiC/Si/Al powders. Baoyan Liang Mingzhi Wang Xiaopu Li Yunchao Mu. Volume 34 Issue 7 December 2011 pp 1309-1311 ...

  11. SHS synthesis of Si-SiC composite powders using Mg and reactants from industrial waste

    Science.gov (United States)

    Chanadee, Tawat

    2017-11-01

    Si-SiC composite powders were synthesized by self-propagating high-temperature synthesis (SHS) using reactants of fly ash-based silica, sawdust-based activated carbon, and magnesium. Fly ash-based silica and sawdust-based activated carbon were prepared from coal mining fly ash and Para rubber-wood sawdust, respectively. The work investigated the effects of the synthesis atmosphere (air and Ar) on the phase and morphology of the SHS products. The SHS product was leached by a two-step acid leaching processes, to obtain the Si-SiC composite powder. The SHS product and SHS product after leaching were characterized by X-ray diffractometry, scanning electron microscopy and energy dispersive X-ray spectrometry. The results indicated that the SHS product synthesized in air consisted of Si, SiC, MgO, and intermediate phases (SiO2, Mg, Mg2SiO4, Mg2Si), whereas the SHS product synthesized in Ar consisted of Si, SiC, MgO and a little Mg2SiO4. The SiC content in the leached-SHS product was higher when Ar was used as the synthesis atmosphere. As well as affecting the purity, the synthesis atmospheres also affected the average crystalline sizes of the products. The crystalline size of the product synthesized in Ar was smaller than that of the product synthesized in air. All of the results showed that fly ash and sawdust could be effective waste-material reactants for the synthesis of Si-SiC composite powders.

  12. On iron contamination in mechanically alloyed Cr-Si powders

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Bruno B. [Universidade do Vale do Paraiba, Instituto de Pesquisa e Desenvolvimento, Sao Jose dos, Campos-SP, CEP 12244-000 (Brazil); Rodrigues, Geovani [Faculdade de Engenharia Quimica de Lorena, Departamento de Engenharia de Materiais, Caixa Postal 116, Lorena-SP, CEP 12600-970 (Brazil); Coelho, Gilberto C. [Faculdade de Engenharia Quimica de Lorena, Departamento de Engenharia de Materiais, Caixa Postal 116, Lorena-SP, CEP 12600-970 (Brazil); Ramos, Alfeu S. [Universidade do Vale do Paraiba, Instituto de Pesquisa e Desenvolvimento, Sao Jose dos, Campos-SP, CEP 12244-000 (Brazil)]. E-mail: alfeu@univap.br

    2005-09-25

    The present work reports on iron contamination and phase transformation during high-energy ball milling from high-purity elemental powder Cr-25Si, Cr-37.5Si, Cr-50Si, and Cr-66Si mixtures (at%) and their subsequent heat treatment. Samples were characterized in the as-milled state as well as after heat treatment by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microanalysis via energy dispersive spectrometry (EDS). Only Cr peaks were observed in Cr-25Si and Cr-37.5Si powders after milling for 200 h, suggesting that amorphous phases can be formed. In Cr-50Si and Cr-66Si powders, the CrSi and CrSi{sub 2} phases were formed during ball milling, respectively. In Cr-25Si and Cr-50Si milled powders, heat-treated at 1200 deg. C for 4 h, the formation of the Cr{sub 3}Si and CrSi phases dissolving up to 15 and 16.9 at%Fe, respectively, was noted. In addition, the ternary Cr{sub 9}Fe{sub 9}Si{sub 2} phase was also formed in heat-treated Cr-25Si powders. A small amount of Cr{sub 5}Si{sub 3} and CrSi{sub 2} was formed in heat-treated Cr-37.5Si and Cr-66Si powders, respectively.

  13. Eutrophication alters Si cycling and litter decomposition in wetlands

    NARCIS (Netherlands)

    Emsens, Willem-Jan; Schoelynck, Jonas; Grootjans, Ab P.; Struyf, Eric; van Diggelen, Rudy

    2016-01-01

    Anthropogenic eutrophication of wetlands may have a significant impact on the global biogeochemical silicon (Si) cycle, as Si filtering by wetland vegetation codetermines fluxes of Si towards the oceans. We experimentally investigated how macronutrient (NPK) enrichment alters total Si storage and Si

  14. PROMOTION OF THE SI(100)-O2 REACTION BY SM

    NARCIS (Netherlands)

    ONSGAARD, J; GHIJSEN, J; JOHNSON, RL; CHRISTIANSEN, M; ORSKOV, F; GODOWSKI, PJ

    1991-01-01

    It is demonstrated that ultrathin and thin films of Sm on Si (001) strongly promote the oxidation of Si. Photoemission measurements of the Si 2p core electrons show binding-energy shifts characteristic of Si2O3 and SiO2. The oxygen binding is conditioned by the presence of Sm, which is also

  15. Lateral boron distribution in polycrystalline SiC source materials

    DEFF Research Database (Denmark)

    Linnarsson, M. K.; Kaiser, M.; Liljedahl, R.

    2013-01-01

    Polycrystalline SiC containing boron and nitrogen are used in growth of fluorescent SiC for white LEDs. Two types of doped polycrystalline SiC have been studied in detail with secondary ion mass spectrometry: sintered SiC and poly-SiC prepared by sublimation in a physical vapor transport setup. T...

  16. Liposomal siRNA for ovarian cancer.

    Science.gov (United States)

    Mangala, Lingegowda S; Han, Hee Dong; Lopez-Berestein, Gabriel; Sood, Anil K

    2009-01-01

    Discovery of RNA interference (RNAi) has been one of the most important findings in the last ten years. In recent years, small interfering RNA (siRNA)-mediated gene silencing is beginning to show substantial promise as a new treatment modality in preclinical studies because of its robust gene selective silencing. However, until recently, delivery of siRNA in vivo was a major impediment to its use as a therapeutic modality. We have used a neutral liposome, 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC), for highly efficient in vivo siRNA delivery. Using siRNA tagged with Alexa-555, incorporated in DOPC liposomes, we have demonstrated efficient intra-tumoral delivery following either intraperitoneal or intravenous injection. Furthermore, EphA2-targeted siRNA in DOPC liposomes showed significant target modulation and anti-tumor efficacy.

  17. DLC-Si protective coatings for polycarbonates

    Directory of Open Access Journals (Sweden)

    Damasceno J.C.

    2003-01-01

    Full Text Available In this work, a-C:H:Si (DLC-Si films were produced onto crystalline silicon and polycarbonate substrates by the rf-PACVD technique from gaseous mixtures of CH4 + SiH4 and C2H2 + SiH4. The effects of self-bias and gas composition upon mechanical and optical properties of the films were investigated. Micro-hardness, residual stress, surface roughness and refractive index measurements were employed for characterization. By incorporating low concentrations of silicon and by exploring the more favorable conditions for the rf-PACVD deposition technique, highly adherent DLC-Si thin films were produced with reduced internal stresses (lower than 1 GPa, high hardness (around 20 GPa and high deposition rates (up to 10 µm/h. Results that show the technological viability of this material for application as protective coatings for polycarbonates are also discussed.

  18. LA GESTION ASSOCIATIVE DE LA PÊCHE EN FRANCE : UNE ANALYSE ÉCONOMIQUE À PARTIR DU CAS DES SALMONIDÉS

    Directory of Open Access Journals (Sweden)

    LE GOFFE P.

    2004-07-01

    Full Text Available L’analyse économique et l’examen des quelques données empiriques disponibles en France incitent à se demander si la gestion associative permet de tirer suffisamment de bien-être de la pêche de loisir en eau douce. Notre analyse s’appuie sur le cas des salmonidés. D’une part, l’effort de pêche est probablement trop important sur les bons parcours faciles d’accès, ce qui peut entraîner des pertes de bien-être dues à la congestion. D’autre part, les propriétaires riverains ne sont pas suffisamment incités à améliorer la qualité de l’environnement, alors que les pêcheurs ont un consentement à payer pour des améliorations. Ces inefficacités s’expliquent par la conjonction de trois phénomènes. Tout d’abord, les droits de propriété, privés, sont atténués par des dispositions législatives. Ensuite, les associations ne contrôlent pas suffisamment l’effort de pêche individuel et collectif. Finalement, les politiques halieutiques sont centrées sur la protection de la ressource et sont, bien que nécessaires, insuffisantes pour maximiser la rente sociale tirée de la pêche. La régulation de l’effort de pêche et la négociation de certains services environnementaux sur la base du principe bénéficiaire-payeur permettraient d’améliorer le bien-être collectif. Des tarifs sociaux permettraient de maintenir l’équité dans l’accès.

  19. Polarized Raman spectroscopy study of NiSi film grown on Si(001) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Li; Ren, Yiming; Tang, Bo; Cheng, Xinhong; Zhang, Xuefei; Xu, Dapeng; Luo, Hijun; Huang, Yunmi [Wenzhou University, Department of Physics, Wenzhou (China)

    2009-11-15

    We report on the growth of NiSi film on Si(001) substrate with an orientation of NiSi[200]//Si[001]. Polarized Raman spectroscopy was used to assign the symmetry of the NiSi Raman peaks. Raman peaks at 213 cm{sup -1}, 295 cm{sup -1}, and 367 cm{sup -1} are assigned to be A{sub g} symmetry and peaks at 196 cm{sup -1}, and 254 cm{sup -1} are B{sub 3g} symmetry. (orig.)

  20. Deep inelastic reactions of /sup 28/Si on /sup 28/Si and /sup 27/Al

    Energy Technology Data Exchange (ETDEWEB)

    Manduchi, C.; Manduchi, M.T.R.; Segato, G.F.; Andolfato, F.

    1986-12-01

    The deep inelastic reactions of /sup 28/Si on /sup 28/Si at incident energies of 125 and 138 MeV, and /sup 28/Si on /sup 27/Al at 130 MeV, have been studied by measuring inclusive fragment distributions, and fragment-fragment coincidences. The experiment employed a coincidence spectrometer consisting of two multiparameter ion chambers. Inclusive measurements exhibit behaviour characteristic of strongly damped processes. Two-fragment exclusive measurements in the /sup 28/Si-/sup 28/Si reaction show interesting selective phenomena in both mass and charge spectra of the emitted fragments.

  1. Growth of CrSi2 Nanostructures Using CrCl2 Powder on Si Substrates

    OpenAIRE

    Wen Li; Meng Erchao; Tomoji Matsushita; Shingo Oda; Daisuke Ishikawa; Kaito Nakane; Hirokazu Tatsuoka

    2013-01-01

    Chromium disilicide (CrSi2) nanostructures were grown by the exposure of Si (111) substrates to CrCl2 vapor in an argon gas flow at atmospheric pressure without using any metal catalyst. Dependence of the growth condition on the structural property was investigated. Hexagonal-shaped CrSi2 microrods were grown at 750 °C with 0.05 g of CrCl2. As the quantity of CrCl2 increased to 0.1 g, the bundle of CrSi2 nanowires with microrods and web-liked CrSi2 nanostructure with turning angles were grown...

  2. High Efficiency Hybrid Solar Cells Using Nanocrystalline Si Quantum Dots and Si Nanowires.

    Science.gov (United States)

    Dutta, Mrinal; Thirugnanam, Lavanya; Trinh, Pham Van; Fukata, Naoki

    2015-07-28

    We report on an efficient hybrid Si nanocrystal quantum dot modified radial p-n junction thinner Si solar cell that utilizes the advantages of effective exciton collection by energy transfer from nanocrystal-Si (nc-Si) quantum dots to underlying radial p-n junction Si nanowire arrays with excellent carrier separation and propagation via the built-in electric fields of radial p-n junctions. Minimization of recombination, optical, and spectrum losses in this hybrid structure led to a high cell efficiency of 12.9%.

  3. High Mobility Transport Layer Structures for Rhombohedral Si/Ge/SiGe Devices

    Science.gov (United States)

    Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Kim, Hyun-Jung (Inventor); Lee, Kunik (Inventor)

    2017-01-01

    An electronic device includes a trigonal crystal substrate defining a (0001) C-plane. The substrate may comprise Sapphire or other suitable material. A plurality of rhombohedrally aligned SiGe (111)-oriented crystals are disposed on the (0001) C-plane of the crystal substrate. A first region of material is disposed on the rhombohedrally aligned SiGe layer. The first region comprises an intrinsic or doped Si, Ge, or SiGe layer. The first region can be layered between two secondary regions comprising n+doped SiGe or n+doped Ge, whereby the first region collects electrons from the two secondary regions.

  4. Evaluation of CVI SiC/SiC Composites for High Temperature Applications

    Science.gov (United States)

    Kiser, D.; Almansour, A.; Smith, C.; Gorican, D.; Phillips, R.; Bhatt, R.; McCue, T.

    2017-01-01

    Silicon carbide fiber reinforced silicon carbide (SiC/SiC) composites are candidate materials for various high temperature turbine engine applications because of their high specific strength and good creep resistance at temperatures of 1400 C (2552 F) and higher. Chemical vapor infiltration (CVI) SiC/SiC ceramic matrix composites (CMC) incorporating Sylramic-iBN SiC fiber were evaluated via fast fracture tensile tests (acoustic emission damage characterization to assess cracking behavior), tensile creep testing, and microscopy. The results of this testing and observed material behavior degradation mechanisms are reviewed.

  5. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  6. Boosting light emission from Si-based thin film over Si and SiO(2) nanowires architecture.

    Science.gov (United States)

    Yu, Zhongwei; Qian, Shengyi; Yu, Linwei; Misra, Soumyadeep; Zhang, Pei; Wang, Junzhuan; Shi, Yi; Xu, Ling; Xu, Jun; Chen, Kunji; Roca i Cabarrocas, Pere

    2015-03-09

    Silicon (Si)-based light emitting thin film has been a key ingredient for all-Si-based optoelectronics. Besides material engineering, adopting a novel 3D photonic architecture represents an effective strategy to boost light excitation and extraction from Si-based thin film material. We here explore the use of a nanowires (NW) framework, grown via vapor-liquid-solid mode, to achieve strongly enhanced yellow-green luminescence from SiN(x)O(y)/NW core-shell structure, with an order of magnitude enhancement compared to co-deposited planar references. We found that choosing geometrically-identical but different NW cores (Si or SiO(2)) can lead to profound influence on the overall light emission performance. Combining parametric investigation and theoretical modeling, we have been able to evaluate the key contributions arising from different mechanisms that include near-field enhancement, 3D light trapping and enhanced light extraction. These new findings indicate a new and effective strategy for strong Si-based thin film light emitting source, while being generic enough to be applicable in a wide variety of other thin film materials.

  7. Luminescence of Nanoporous Si and ALD-Deposited ZnO on Nanoporous Si Substrate

    Science.gov (United States)

    Pham, Vuong-Hung; Tam, Phuong Dinh; Dung, Nguyen Huu; Nguyen, Duy-Hung; Huy, Pham Thanh

    2017-08-01

    This paper reports the attempt at synthesizing nanoporous silicon (Si) with a dendritic-like structure and atomic layer deposition (ALD) of ZnO on nanoporous Si to control light emission intensity and emission center by applying an optimum voltage, etching time and thickness of ZnO layer. The dendritic-like structure of nanoporous Si was formed with low etching voltages of 5-10 V. Fourier transform infrared absorption spectra of the nanoporous Si reveals that the intensities of hydride stretching, SiH2 scissor mode and Si-O-Si vibration peak increase with the increasing of etching time. The formation of a thick dendritic-like structure with an increasing SiH2 bond resulted in significant enhancement of luminescence. In addition, the ALD-deposited ZnO layer on nanoporous Si resulted in light emission from both ZnO and nanoporous Si under a single excitation source. These results suggest the potential application of an ALD-deposited ZnO layer on nanoporous Si in designing materials for advanced optoelectronics.

  8. Improving Passivation Process of Si Nanocrystals Embedded in SiO2 Using Metal Ion Implantation

    Directory of Open Access Journals (Sweden)

    Jhovani Bornacelli

    2013-01-01

    Full Text Available We studied the photoluminescence (PL of Si nanocrystals (Si-NCs embedded in SiO2 obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm inside the SiO2 achieving a robust and better protected system. After metal ion implantation (Ag or Au, and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO2 matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H2/N2 and Ar to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.

  9. Electronic Properties of Si-Hx Vibrational Modes at Si Waveguide Interface.

    Science.gov (United States)

    Bashouti, Muhammad Y; Yousefi, Peyman; Ristein, Jürgen; Christiansen, Silke H

    2015-10-01

    Attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy in suite with Kelvin probe were conjugated to explore the electronic properties of Si-Hx vibrational modes by developing Si waveguide with large dynamic detection range compared with conventional IR. The Si 2p emission and work-function related to the formation and elimination of Si-Hx bonds at Si surfaces are monitored based on the detection of vibrational mode frequencies. A transition between various Si-Hx bonds and thus related vibrational modes is monitored for which effective momentum transfer could be demonstrated. The combination of the aforementioned methods provides for results that permit a model for the kinetics of hydrogen termination of Si surfaces with time and advanced surface characterizing of hybrid-terminated semiconducting solids.

  10. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  11. Light emissions from LiNbO sub 3 /SiO sub 2 /Si structures

    CERN Document Server

    Wu, X L; Tang, N; Deng, S S; Bao, X M

    2003-01-01

    LiNbO sub 3 (LN) films with a high degree of (006) texture were deposited on Si-based dense SiO sub 2 layers by pulsed laser deposition. After annealing, the LN/SiO sub 2 /Si structures were revealed to have ultraviolet-, green-, and red-emitting properties related to self-trapped excitons and E' defect pairs in the SiO sub 2 surface, which are induced by the photorefractive effect of the LN films. The emission wavelength can be tuned by introducing different dopants into the LN films. Waveguiding properties of the structures were demonstrated. The results obtained indicate that the LN/SiO sub 2 /Si structures could be expected to have important applications in modern optoelectronic integration. (letter to the editor)

  12. Effect of PECVD SiNx/SiOyNx-Si interface property on surface passivation of silicon wafer

    Science.gov (United States)

    Jia, Xiao-Jie; Zhou, Chun-Lan; Zhu, Jun-Jie; Zhou, Su; Wang, Wen-Jing

    2016-12-01

    It is studied in this paper that the electrical characteristics of the interface between SiOyNx/SiNx stack and silicon wafer affect silicon surface passivation. The effects of precursor flow ratio and deposition temperature of the SiOyNx layer on interface parameters, such as interface state density Dit and fixed charge Qf, and the surface passivation quality of silicon are observed. Capacitance-voltage measurements reveal that inserting a thin SiOyNx layer between the SiNx and the silicon wafer can suppress Qf in the film and Dit at the interface. The positive Qf and Dit and a high surface recombination velocity in stacks are observed to increase with the introduced oxygen and minimal hydrogen in the SiOyNx film increasing. Prepared by deposition at a low temperature and a low ratio of N2O/SiH4 flow rate, the SiOyNx/SiNx stacks result in a low effective surface recombination velocity (Seff) of 6 cm/s on a p-type 1 Ω·cm-5 Ω·cm FZ silicon wafer. The positive relationship between Seff and Dit suggests that the saturation of the interface defect is the main passivation mechanism although the field-effect passivation provided by the fixed charges also make a contribution to it. Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA050302) and the National Natural Science Foundation of China (Grant No. 61306076).

  13. Apport de l'évaluation de la cognition dans une tâche de vie quotidienne chez des patients cérébrolésés : génération et exécution d'un script de cuisine

    National Research Council Canada - National Science Library

    Baguena, N; Thomas-Antérion, C; Sciessere, K; Truche, A; Extier, C; Guyot, E; Paris, N

    2006-01-01

    ... de la tâche proposée. Ainsi, Le Gall et al. [18] ont montré la capacité de patients frontaux à rétablir correctement l'organisation séquentielle et hiérarchique d'un script alors que Sirig...

  14. Experimental and thermodynamic assessments of substitutions in the AlFeSi, FeMnSi, FeSiZr and AlCaFeSi systems (65 wt % Si) - solidification simulation

    Energy Technology Data Exchange (ETDEWEB)

    Gueneau, C. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes d`Enrichissement]|[Paris-11 Univ., 91 - Orsay (France)]|[Compagnie de Produits Chimiques et Electrometallurgiques Pechiney, 74 - Passy-Chedde (France). Lab. Graphitation; Servant, C. [Paris-11 Univ., 91 - Orsay (France); Ansara, I. [Ecole Nationale Superieure d`Electrochimie et d`Electrometallurgie, 38 - Grenoble (France)

    1994-12-31

    The substitutions of Al <-> Si, Fe <-> Mn and Fe <-> Zr in some intermetallic compounds of the Al-Fe-Si, Fe-Mn-Si and Fe-Si-Zr systems are modelled in the Si-rich corner using a two sublattice model. The solidification paths of the studied alloys are determined at equilibrium. The ascalculated phase volume fractions of the alloys are compared to the experimental ones. Finally, a solidification simulation using the Gulliver-Scheil`s model is performed in order to explain the formation of some precipitates experimentally observed. (authors). 14 figs., 19 refs.

  15. Compact hybrid Si microring lasers

    Science.gov (United States)

    Liang, Di; Bowers, John E.; Fiorentino, Marco; Beausoleil, Raymond G.

    2010-02-01

    In this paper we review the recent progress in developing compact microring lasers on the hybrid silicon platform. A simplified self-aligned process is used to fabricate devices as small as 15 μm in diameter. The optically-pumped, continuous wave (cw) devices show low threshold carrier density, comparable to the carrier density to reach material transparency. In the electrically-pumped lasers, the short cavity length leads to the minimum laser threshold less than 5 mA in cw operation. The maximum cw lasing temperature is up to 65 °C. Detailed studies in threshold as a function of coupling coefficient and bus waveguide width are presented. Surface recombination at the dry-etched exposed interface is investigated qualitatively by studying the current-voltage characteristics. Ring resonator-based figures of merits including good spectral purity and large side-mode suppression ratio are demonstrated. Thermal impedance data is extracted from temperature-dependent spectral measurement, and buried oxide layer in silicon-on-insulator wafer is identified as the major thermal barrier to cause high thermal impedance for small-size devices. The demonstrated compact hybrid ring lasers have low power consumption, small footprint and dynamic performance. They are promising for Si-based optical interconnects and flip-flop applications.

  16. Gold and silver/Si nanocomposite layers

    Energy Technology Data Exchange (ETDEWEB)

    Kleps, Irina [National Institute for Research and Development in Microtechnologies (IMT-Bucharest), P.O. Box 38-160, Bucharest (Romania)], E-mail: irinak@imt.ro; Danila, Mihai; Angelescu, Anca; Miu, Mihaela; Simion, Monica; Ignat, Teodora; Bragaru, Adina [National Institute for Research and Development in Microtechnologies (IMT-Bucharest), P.O. Box 38-160, Bucharest (Romania); Dumitru, Lucia; Teodosiu, Gabriela [Institute of Biology, 296 Splaiul Independentei, P.O. Box 56-53, Bucharest, 060031 (Romania)], E-mail: biologie@ibiol.ro

    2007-09-15

    Ag and Au nanolayers were realised by physical and chemical deposition methods on porous silicon (PS) nanostructured surfaces for biomedical applications: support for living cells, biodegradable material for the slow release of drugs/minerals, and as a bioactive material for scaffolds. Au nanoparticles on nanocrystalline Si are widely used in increasing substrate biocompatibility properties. It has an electrochemical potential of + 0.332 mV and surface energy around 25 erg/cm{sup 2}, close to those of living tissues. The Au nanocrystallites orientation on nanocrystalline Si substrates is also of great interest for application in biochemistry; the Au (111)/nc-Si surface has a higher density of atoms compared with Au (100); this favours the attachment of a higher number of atoms and bio-molecules on the gold surface. Ag nanoparticles on nanocrystalline Si are important for the latter's anti-microbial properties. In minute concentrations, Ag is highly toxic to germs while relatively non-toxic to human cells. Microbes are unlikely to develop a resistance against silver, as they do against conventional and highly targeted antibiotics. The Au and Ag nanoparticles/silicon nanocomposite layers as-deposited and thermally treated were investigated by optical microscopy, X-ray diffraction, and biological tests using eukaryotic and prokaryotic cell cultures. The experimental results sustain the use of Au/Si and Ag/Si or combined Ag/Au/Si nanocomposite structures as biocompatible and anti-microbial matrix.

  17. Facile Synthesis of Si@SiC Composite as an Anode Material for Lithium-Ion Batteries.

    Science.gov (United States)

    Ngo, Duc Tung; Le, Hang T T; Pham, Xuan-Manh; Park, Choong-Nyeon; Park, Chan-Jin

    2017-09-27

    Here, we propose a simple method for direct synthesis of a Si@SiC composite derived from a SiO2@C precursor via a Mg thermal reduction method as an anode material for Li-ion batteries. Owing to the extremely high exothermic reaction between SiO2 and Mg, along with the presence of carbon, SiC can be spontaneously produced with the formation of Si. The synthesized Si@SiC was composed of well-mixed SiC and Si nanocrystallites. The SiC content of the Si@SiC was adjusted by tuning the carbon content of the precursor. Among the resultant Si@SiC materials, the Si@SiC-0.5 sample, which was produced from a precursor containing 4.37 wt % of carbon, exhibits excellent electrochemical characteristics, such as a high first discharge capacity of 1642 mAh g(-1) and 53.9% capacity retention following 200 cycles at a rate of 0.1C. Even at a high rate of 10C, a high reversible capacity of 454 mAh g(-1) was obtained. Surprisingly, at a fixed discharge rate of C/20, the Si@SiC-0.5 electrode delivered a high capacity of 989 mAh g(-1) at a charge rate of 20C. In addition, a full cell fabricated by coupling a lithiated Si@SiC-0.5 anode and a LiCoO2 cathode exhibits excellent cyclability over 50 cycles. This outstanding electrochemical performance of Si@SiC-0.5 is attributed to the SiC phase, which acts as a buffer layer that stabilizes the nanostructure of the Si active phase and enhances the electrical conductivity of the electrode.

  18. Light trapping of crystalline Si solar cells by use of nanocrystalline Si layer plus pyramidal texture

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Kentaro; Nonaka, Takaaki; Onitsuka, Yuya; Irishika, Daichi; Kobayashi, Hikaru, E-mail: h.kobayashi@sanken.osaka-u.ac.jp

    2017-02-15

    Highlights: • Ultralow reflectivity Si wafers with light trapping effect can be obtained by forming a nanocrystalline Si layer on pyramidal textured Si surfaces. • Surface passivation using phosphosilicate glass improved minority carrier lifetime of the nanocrystalline Si layer/Si structure. • A high photocurrent density of 40.1 mA/cm{sup 2}, and a high conversion efficiency of 18.5% were achieved. - Abstract: The surface structure chemical transfer (SSCT) method has been applied to fabrication of single crystalline Si solar cells with 170 μm thickness. The SSCT method, which simply involves immersion of Si wafers in H{sub 2}O{sub 2} plus HF solutions and contact of Pt catalyst with Si taking only ∼30 s for 6 in. wafers, can decrease the reflectivity to less than 3% by the formation of a nanocrystalline Si layer. However, the reflectivity of the nanocrystalline Si layer/flat Si surface/rear Ag electrode structure in the wavelength region longer than 1000 nm is high because of insufficient absorption of incident light. The reflectivity in the long wavelength region is greatly decreased by the formation of the nanocrystalline Si layer on pyramidal textured Si surfaces due to an increase in the optical path length. Deposition of phosphosilicate glass (PSG) on the nanocrystalline Si layer for formation of pn-junction does not change the ultralow reflectivity because the surface region of the nanocrystalline Si layer possesses a refractive index of 1.4 which is nearly the same as that of PSG of 1.4–1.5. The PSG layer is found to passivate the nanocrystalline Si layer, which is evident from an increase in the minority carrier lifetime from 12 to 44 μs. Hydrogen treatment at 450 °C further increases the minority carrier lifetime approximately to a doubled value. The solar cells with the Si layer/pyramidal Si substrate/boron-diffused back surface field/Ag rear electrode> structure show a high conversion efficiency of 18

  19. Irradiation test of high density Si material

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Man Soon; Choo, Kee Nam; Lee, Chul Yong; Yang, Seong Woo; Shim, Kyue Taek; Park, Sang Jun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    The feasibility of irradiation test for the high-density Si material entrusted by Guju Inc. was reviewed. The high density Si material is used for a sealing of the penetration holes of piping at the nuclear power plants. The irradiation test was performed and the density changes between before and after irradiation test were measured. The irradiation tests were performed 2 times for 1 day and 20 days at IP 4 hole of HANARO. The 3 Si specimens irradiated were without flaws and the density changes after irradiation were successfully measured. The result satisfies the requirement of the design specification.

  20. Modellazione efficiente agli elementi finiti per l’analisi a collasso di strutture incollate complesse

    Directory of Open Access Journals (Sweden)

    E. Dragoni

    2009-07-01

    Full Text Available Il lavoro verifica l’applicabilità di un modello semplificato agli elementi finiti per l’analisi a collasso post elastico di strutture incollate complesse in parete sottile. Al fine di superare le limitazioni dei modelli di letteratura come l’uso di elementi speciali, il lavoro sfrutta un modello ridotto già presentato dagli autori in campo elastico. Tale modello è basato sulla rappresentazione degli aderendi mediante elementi semistrutturali (piastre o gusci e dell’adesivo per mezzo di speciali elementi coesivi. La continuità strutturale tra aderendi e adesivo è ottenuta mediante vincoli interni (tied mesh che accomunano i gradi di libertà dei nodi mutuamente affacciati di aderendi ed adesivo. La struttura analizzata è un simulacro di incollaggio industriale e produce nella strato adesivo una sollecitazione complessa, analizzabile solo con modelli numerici. Si considera una struttura tubolare in parete sottile a sezione quadrata, fatta di due spezzoni posti testa a testa e incollati con fazzoletti di lamiera sui quattro lati. La struttura è sottoposta a flessione a tre punti fino al cedimento e la zona incollata posta disassata rispetto al punto di applicazione del carico riceve una sollecitazione indiretta. I risultati dell’analisi FEM, confrontati direttamente con le curve sperimentali forza-spostamento, evidenziano una buona accuratezza del metodo, in termini di rigidezza, forza massima e comportamento post elastico della struttura, accompagnati da ridotte dimensioni del modello e tempi di calcolo molto contenuti. Grazie a questi vantaggi, la procedura si presta ad effettuare l’analisi di strutture incollate complesse, altrimenti ingestibili se affrontate con una modellazione agli elementi finiti tradizionale.

  1. Superficial biopsy of the cervix: new technique

    Directory of Open Access Journals (Sweden)

    Ettore De Girolami

    2002-06-01

    Full Text Available Cytological examination of the cervix in all patients is considered a necessity. A new technique of superficial biopsy is described and advantages en. numeratedEl Autor presenta una nueva técnica para biopsia superficial, considerando la necesidad de hacer rutinariamente a todas las pacientes el examen citológico del cérvix. La muestra se toma con el extremo de un aplicador cubierto de gaza. Este dispositivo, humedecido previamente en una solución de etanol, metanol y éter etílico, se aplica inmediatamente al cérvix del útero y, dándole un movimiento como el de las manecillas del reloj, se toma la muestra con la que se hacen frotis por aposición que se colorean por el método de Giemsa. Esta técnica ofrece la ventaja de que el tejido en estudio se adhiere perfectamente a la gaza, la cual, con el movimiento de rotación, desprende las células del "os uteri", las que son fijadas al mismo tiempo. La preparación del dispositivo es sumamente sencilla. La prueba resulta de bajo costo como de breve y fácil realizaciónL' Autore prende in considerazione l'utilitá dell' esame citologico del collo dell'utero, fatto rutinariamente a tutte le pazienti. Si descrive una nuova tecnica di biopsia superficiale che oltfe ad offrire dei vantaggi é di poca spesa e si puó eseguire con facilitá ed in breve tempo

  2. Removal of B from Si by Hf addition during Al–Si solvent refining process

    Science.gov (United States)

    Lei, Yun; Ma, Wenhui; Sun, Luen; Wu, Jijun; Dai, Yongnian; Morita, Kazuki

    2016-01-01

    Abstract A small amount of Hf was employed as a new additive to improve B removal in the electromagnetic solidification refinement of Si with an Al–Si melt, because Hf has a very strong affinity for B. The segregation ratio of Hf between the solid Si and Al–Si melt was estimated to range from 4.9 × 10−6 to 8.8 × 10−7 for Al concentrations of 0 to 64 at.%, respectively. The activity coefficient of Hf in solid Si at its infinite dilution was also estimated. A small addition of Hf (Hf addition, slower cooling rate, and Al-rich Al–Si melt as the refining solvent removed B more efficiently. B in Si could be removed as much as 98.2% with 410 ppma Hf addition when the liquidus temperature of the Al–Si melt was 1173 K and the cooling rate was 4.5–7.6 K min–1. The B content in Si could be controlled from 153 ppma to 2.7 ppma, which meets the acceptable level for solar-grade Si. PMID:27877853

  3. Removal of B from Si by Hf addition during Al-Si solvent refining process.

    Science.gov (United States)

    Lei, Yun; Ma, Wenhui; Sun, Luen; Wu, Jijun; Dai, Yongnian; Morita, Kazuki

    2016-01-01

    A small amount of Hf was employed as a new additive to improve B removal in the electromagnetic solidification refinement of Si with an Al-Si melt, because Hf has a very strong affinity for B. The segregation ratio of Hf between the solid Si and Al-Si melt was estimated to range from 4.9 × 10-6 to 8.8 × 10-7 for Al concentrations of 0 to 64 at.%, respectively. The activity coefficient of Hf in solid Si at its infinite dilution was also estimated. A small addition of Hf (Hf addition, slower cooling rate, and Al-rich Al-Si melt as the refining solvent removed B more efficiently. B in Si could be removed as much as 98.2% with 410 ppma Hf addition when the liquidus temperature of the Al-Si melt was 1173 K and the cooling rate was 4.5-7.6 K min-1. The B content in Si could be controlled from 153 ppma to 2.7 ppma, which meets the acceptable level for solar-grade Si.

  4. Dall’inferno si leva un canto. Italo Calvino e «l’eco lontana del silenzio»

    Directory of Open Access Journals (Sweden)

    Andrea Cannas

    2015-07-01

    Full Text Available Nella produzione narrativa di Italo Calvino l’explicit può circoscrivere lo spazio verso cui il 'rumore' del mondo s’avanza a minacciare l’ordine della finzione – e, viceversa, il finale dell’opera può risultare l’ultimo baluardo per mezzo del quale il senso, di cui la finzione è la più strenua attestazione, si sforza di resistere al non senso che proviene dal caos della Storia. Il cielo di pietra, Un re in ascolto, racconti dedicati al valore del canto e, per contro, alla minaccia acustica scoperchiata dalle indiavolate metropoli del nostro tempo, insieme all’epilogo de Le città invisibili rappresentano tre casi emblematici in cui la finzione digrada verso la realtà marcando, su un piano finalmente sincronico, l’estrema frontiera da cui l’autore contempla la propria comunità d’appartenenza – ed eventualmente riflette sul potere, se non salvifico, per lo meno discriminante della parola scritta. Da questa prospettiva il silenzio è al contempo il presupposto e il movimento cui dovrebbe tendere ogni scrittura: costituisce in definitiva per Calvino l’opportunità di discernere per cogliere finalmente l’essenziale.

  5. Removal of C and SiC from Si and FeSi during ladle refining and solidification

    Energy Technology Data Exchange (ETDEWEB)

    Klevan, Ole Svein

    1997-12-31

    The utilization of solar energy by means of solar cells requires the Si to be very pure. The purity of Si is important for other applications as well. This thesis mainly studies the total removal of carbon from silicon and ferrosilicon. The decarburization includes removal of SiC particles by stirring and during casting in addition to reduction of dissolved carbon by gas purging. It was found that for three commercial qualities of FeSi75, Refined, Gransil, and Standard lumpy, the refined quality is lowest in carbon, followed by Gransil and Standard. A decarburization model was developed that shows the carbon removal by oxidation of dissolved carbon to be a slow process at atmospheric pressure. Gas stirring experiments have shown that silicon carbide particles are removed by transfer to the ladle wall. The casting method of ferrosilicon has a strong influence on the final total carbon content in the commercial alloy. Shipped refined FeSi contains about 100 ppm total carbon, while the molten alloy contains roughly 200 ppm. The total carbon out of the FeSi-furnace is about 1000 ppm. It is suggested that low values of carbon could be obtained on an industrial scale by injection of silica combined with the use of vacuum. Also, the casting system could be designed to give low carbon in part of the product. 122 refs., 50 figs., 24 tabs.

  6. Half-life of 31Si

    CERN Document Server

    D'Agostino, Giancarlo; Mana, Giovanni; Oddone, Massimo

    2016-01-01

    Half-life values are widely used in nuclear chemistry to model the exponential decay of the quantified radionuclides. The analysis of existing data reveals a general lack of information on the performed experiments and an almost complete absence of uncertainty budgets. This is the situation for 31Si, the radionuclide produced via neutron capture reaction recently used to quantify trace amounts of 30Si in a sample of the silicon material highly enriched in 28Si and used for the determination of the Avogadro constant. In order to improve the quality of the now recommended 157.36(26) min value, we carried out repeated observations of the 31Si decay rate via gamma-ray spectrometry measurements. This paper reports the result we obtained, including details of the experiment and the evaluation of the uncertainty.

  7. Pr5Si3N9

    Directory of Open Access Journals (Sweden)

    Saskia Lupart

    2009-06-01

    Full Text Available Single crystals of Pr5Si3N9, pentapraseodymium trisilicon nonanitride, were obtained by the reaction of elemental praseodymium with silicon diimide in a radio-frequency furnace at 1873 K. The crystal structure consists of a chain-like Si—N substructure of corner-sharing SiN4 tetrahedra. An additional Q1-type [SiN4] unit is attached to every second tetrahedron directed alternately in opposite directions. The resulting branched chains interlock with each other, building up a three-dimensional structure. The central atoms of the Q1-type [SiN4] unit and of its attached tetrahedron are situated on a mirror plane, as are two of the four crystallographically unique Pr3+ ions. The latter are coordinated by six to ten N atoms, with Pr—N distances similar to those of other rare earth nitridosilicates.

  8. High-efficiency si/polymer hybrid solar cells based on synergistic surface texturing of Si nanowires on pyramids.

    Science.gov (United States)

    He, Lining; Lai, Donny; Wang, Hao; Jiang, Changyun; Rusli

    2012-06-11

    An efficient Si/PEDOT:PSS hybrid solar cell using synergistic surface texturing of Si nanowires (SiNWs) on pyramids is demonstrated. A power conversion efficiency (PCE) of 9.9% is achieved from the cells using the SiNW/pyramid binary structure, which is much higher than similar cells based on planar Si, pyramid-textured Si, and SiNWs. The PCE is the highest reported to-date for hybrid cells based on Si nanostructures and PEDOT. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Si/SiC heterojunction optically controlled transistor with charge compensation layer

    Directory of Open Access Journals (Sweden)

    Pu Hongbin

    2016-01-01

    Full Text Available A novel n-SiC/p-Si/n-Si optically controlled transistor with charge compensation layer has been studied in the paper. The performance of the device is simulated using Silvaco Atlas tools, which indicates excellent performances of the device in both blocking state and conducting state. The device also has a good switching characteristic with 0.54μs as rising time and 0.66μs as falling time. With the charge compensation layer, the breakdown voltage and the spectral response intensity of the device are improved by 90V and 33A/W respectively. Compared with optically controlled transistor without charge compensation layer, the n-SiC/p-Si/n-Si optically controlled transistor with charge compensation layer has a better performance.

  10. Structural and Morphological Investigation of Pendeo-Epitaxy 3C-SiC on Si Substrates

    Science.gov (United States)

    Kim, Byeung C.; Capano, Michael A.

    2008-05-01

    Successful pendeo-epitaxy growth of cubic silicon carbide (3C-SiC) on off-axis Si(001) substrates was achieved. The structural and morphological characteristics of pendeo-epitaxy 3C-SiC were strongly affected by underlying stripes and seed layer thickness. Stripes perpendicular to the Si substrate off-axis provide about three times faster lateral growth rate compared with parallel oriented stripes. Root-mean-square (RMS) measurements using atomic force microscope (AFM) indicate that the surface morphology of Pendeo-epitaxy 3C-SiC films remarkably improves with increasing seed layer thickness: from 9.8 nm for 3 μm thickness to 0.5 nm for 10 μm thickness. These effects on pendeo-epitaxy 3C-SiC are discussed with scanning electron microscopy (SEM) and AFM investigation.

  11. Structure and chemistry of passivated SiC/SiO{sub 2} interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Houston Dycus, J.; Xu, Weizong; LeBeau, James M. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907 (United States); Lichtenwalner, Daniel J.; Hull, Brett; Palmour, John W. [Power Devices R& D, Wolfspeed, A Cree Company, Research Triangle Park, North Carolina 27709 (United States)

    2016-05-16

    Here, we report on the chemistry and structure of 4H-SiC/SiO{sub 2} interfaces passivated either by nitric oxide annealing or Ba deposition. Using aberration corrected scanning transmission electron microscopy and spectroscopy, we find that Ba and N remain localized at SiC/SiO{sub 2} interface after processing. Further, we find that the passivating species can introduce significant changes to the near-interface atomic structure of SiC. Specifically, we quantify significant strain for nitric oxide annealed sample where Si dangling bonds are capped by N. In contrast, strain is not observed at the interface of the Ba treated samples. Finally, we place these results in the context of field effect mobility.

  12. The Effect of Si Morphology on Machinability of Al-Si Alloys

    Directory of Open Access Journals (Sweden)

    Muhammet Uludağ

    2015-12-01

    Full Text Available Many of the cast parts require some sort of machining like milling, drilling to be used as a finished product. In order to improve the wear properties of Al alloys, Si is added. The solubility of Si in Al is quite low and it has a crystallite type structure. It behaves as particulate metal matrix composite which makes it an attractive element. Thus, the wear and machinability properties of these type of alloys depend on the morphology of Si in the matrix. In this work, Sr was added to alter the morphology of Si in Al-7Si and Al-12Si. Cylindrical shaped samples were cast and machinability characteristics of Sr addition was studied. The relationship between microstructure and machinability was evaluated.

  13. Brazing of SiC using Cu-Si non reactive alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gasse, A. [C.E.A., CEREM-DEM, Grenoble (France); Chaumat, G. [C.E.A., CEREM-DEM, Grenoble (France); Rado, C. [INPG/LTCM-ENSEEG, Saint Martin d`Heres (France); Eustathopoulos, N. [INPG/LTCM-ENSEEG, Saint Martin d`Heres (France)

    1995-12-31

    SiC was brazed with a Cu 24 at% Si alloy under high vacuum at 1473 K. This alloy well wets SiC without any measurable reactivity and after cooling, leads to an interface which appears to be strong. It was found that the degree of filling of the joint by the alloy depends mainly on the geometry of the ceramic-metal-vapour system. It is shown that geometrical factors influence the kinetics of deoxidation of both alloys and SiC surfaces and, as a consequence, considerably modify the wetting kinetics and filling of the joint. Successful helium-tight tube/plate brazed joints have been obtained. Nevertheless, thermal expansion mismatch remains considerable between the SiC and the Cu-Si alloy. Further work is needed to improve the mechanical behaviour of such junctions to avoid crack formation. (orig./MM)

  14. Silicon Photonics Cloud (SiCloud)

    DEFF Research Database (Denmark)

    DeVore, P. T. S.; Jiang, Y.; Lynch, M.

    2015-01-01

    Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths.......Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths....

  15. RBS using {sup 28}Si beams

    Energy Technology Data Exchange (ETDEWEB)

    Ophel, T.R. [Australian National Univ., Canberra, ACT (Australia); Mitchell, I.V. [University of Western Ontario, London, ON (Canada). Dept. of Physics

    1996-12-31

    Measurements of RBS using {sup 28}Si beams have been made to evaluate the enhancement of sensitivity that should obtain from kinematic suppression of silicon substrate scattering. Two detection methods were tried. Aside from a surface barrier detector, a magnetic spectrometer, instrumented with a multi-electrode gas focal plane detector, was used to indicate the resolution attainable with low energy {sup 28}Si ions. The results confirm that kinematically suppressed RBS does provide greatly improved sensitivity. 5 refs., 2 figs.

  16. Temperature-dependent 29Si incorporation during deposition of highly enriched 28Si films

    Science.gov (United States)

    Dwyer, K. J.; Kim, H. S.; Simons, D. S.; Pomeroy, J. M.

    2017-11-01

    In this study, we examine the mechanisms leading to 29Si incorporation into highly enriched 28Si films deposited by hyperthermal ion beams at elevated temperatures in the dilute presence of natural abundance silane (SiH4) gas. Enriched 28Si is a critical material in the development of quantum information devices because 28Si is free of nuclear spins that cause decoherence in a quantum system. We deposit epitaxial thin films of 28Si enriched in situ beyond 99.999 98% 28Si onto Si(100) using an ion-beam deposition system and seek to develop the ability to systematically vary the enrichment and measure the impact on quantum coherence. We use secondary ion mass spectrometry to measure the residual 29Si isotope fraction in enriched samples deposited from ≈250 ∘C up to 800 °C. The 29Si isotope fraction is found to increase from 4 ×10-6 at around 800 °C. From these data, we estimate the temperature dependence of the incorporation fraction s of SiH4, which increases sharply from about 2.9 ×10-4 at 500 °C to 2.3 ×10-2 at 800 °C. We determine an activation energy of 1.00(8) eV associated with the abrupt increase in incorporation and conclude that below 500 °C, a temperature-independent mechanism such as activation from ion collisions with adsorbed SiH4 molecules is the primary incorporation mechanism. Direct incorporation from the adsorbed state is found to be minimal.

  17. Antioxidant migration resistance of SiOxlayer in SiOx/PLA coated film.

    Science.gov (United States)

    Huang, Chongxing; Zhao, Yuan; Su, Hongxia; Bei, Ronghua

    2018-02-01

    As novel materials for food contact packaging, inorganic silicon oxide (SiO x ) films are high barrier property materials that have been developed rapidly and have attracted the attention of many manufacturers. For the safe use of SiO x films for food packaging it is vital to study the interaction between SiO x layers and food contaminants, as well as the function of a SiO x barrier layer in antioxidant migration resistance. In this study, we deposited a SiO x layer on polylactic acid (PLA)-based films to prepare SiO x /PLA coated films by plasma-enhanced chemical vapour deposition. Additionally, we compared PLA-based films and SiO x /PLA coated films in terms of the migration of different antioxidants (e.g. t-butylhydroquinone [TBHQ], butylated hydroxyanisole [BHA], and butylated hydroxytoluene [BHT]) via specific migration experiments and then investigated the effects of a SiO x layer on antioxidant migration under different conditions. The results indicate that antioxidant migration from SiO x /PLA coated films is similar to that for PLA-based films: with increase of temperature, decrease of food simulant polarity, and increase of single-sided contact time, the antioxidant migration rate and amount in SiO x /PLA coated films increase. The SiO x barrier layer significantly reduced the amount of migration of antioxidants with small and similar molecular weights and similar physical and chemical properties, while the degree of migration blocking was not significantly different among the studied antioxidants. However, the migration was affected by temperature and food simulant. Depending on the food simulants considered, the migration amount in SiO x /PLA coated films was reduced compared with that in PLA-based films by 42-46%, 44-47%, and 44-46% for TBHQ, BHA, and BHT, respectively.

  18. Si nanoparticle-decorated Si nanowire networks for Li-ion battery anodes

    KAUST Repository

    Hu, Liangbing

    2011-01-01

    We designed and fabricated binder-free, 3D porous silicon nanostructures for Li-ion battery anodes, where Si nanoparticles electrically contact current collectors via vertically grown silicon nanowires. When compared with a Si nanowire anode, the areal capacity was increased by a factor of 4 without having to use long, high temperature steps under vacuum that vapour-liquid-solid Si nanowire growth entails. © 2011 The Royal Society of Chemistry.

  19. Stability of Ta-encapsulating Si clusters on Si(111)-(7x7) surfaces

    CERN Document Server

    Uchida, N; Miyazaki, T; Kanayama, T

    2003-01-01

    Tantalum containing Si cluster ions TaSi sub 1 sub 0 sub - sub 1 sub 3 H sub x sup + were synthesized in an ion trap and deposited onto Si(111)-(7x7) surfaces with a kinetic energy of 18 eV. Scanning tunnelling microscope observations revealed that the clusters adsorbed on the surface without decomposition, consistent with ab initio calculation results, that predicted the clusters would have stable Si-cage structures with a Ta atom at the centre. (rapid communication)

  20. Hybrid Integrated Si/SiN Platforms for Wideband Optical Processing

    Science.gov (United States)

    2017-05-08

    this issue, we developed a new techniques for fabrication of the hybrid Si/SiN material platform based on a high-quality wafer bonding process (Figure 4...The main advantage of this new process based on wafer bonding is the possibility of wafer-scale development of Si/SiN material platform that...34 into the die, the trapped air and chemical by-products of bonding can escape the interface, resulting in the void-free fusion of the two dies

  1. SiCGe/SiC heterojunction and its MEDICI simulation of optoelectronic characteristics

    Science.gov (United States)

    Lü, Zheng; Chen, Zhi-Ming; Pu, Hong-Bin

    2005-06-01

    Optoelectronic characteristics of the SiC1-xGex /SiC heterojunction photodiode are simulated using MEDICI after the theoretical investigation of key properties for SiC1-xGex. The calculations show that SiC1-xGex /SiC with x=0.3 may have a small lattice mismatch with 3C-SiC and a good response to the visible light and the near infrared light. The response spectrum of the SiC1-xGex /SiC heterojunction photodiode, which consists of a p-type SiC1-xGex absorption layer with a doping concentration of 1×1015cm-3, a thickness of 1.6μm and x=0.3, has a peak of 250mA/W at 0.52μm and the peak can even reach 102mA/W at 0.7μm.

  2. Specimen size effect considerations for irradiation studies of SiC/SiC

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Henager, C.H. Jr.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    For characterization of the irradiation performance of SiC/SiC, limited available irradiation volume generally dictates that tests be conducted on a small number of relatively small specimens. Flexure testing of two groups of bars with different sizes cut from the same SiC/SiC plate suggested the following lower limits for flexure specimen number and size: Six samples at a minimum for each condition and a minimum bar size of 30 x 6.0 x 2.0 mm{sup 3}.

  3. Next Generation, Si-Compatible Materials and Devices in the Si-Ge-Sn System

    Science.gov (United States)

    2015-10-09

    Photoluminescence from Ge1-x-ySixSny, ternaries and LEDs: Synthesis of light emitting Ge1-x-ySixSny, materials with tunable wavelengths over a wide range in the...AFRL-AFOSR-VA-TR-2016-0044 Next generation, Si-compatible materials and devices in the Si-Ge-Sn system John Kouvetakis ARIZONA STATE UNIVERSITY Final...4. TITLE AND SUBTITLE Next generation, Si-compatible materials and devices in the Si-Ge-Sn system 5a. CONTRACT NUMBER FA9550-12-1-0208 5b. GRANT

  4. Electrical Conductivity of SiC/Si Composites Obtained from Wood Preforms

    Science.gov (United States)

    Béjar, Marco Antonio; Mena, Rodrigo; Toro, Juan Esteban

    2011-02-01

    Biomorphic SiC/Si composites were produced from pine and beech wood, and the corresponding electrical conductivity was determined as a function of the temperature. Firstly, wood preforms were pyrolized at 1050 °C in nitrogen. Then, the pyrolized preforms were impregnated with liquid silicon and kept at 1600 °C for 2 h in vacuum. The SiC/Si composites were obtained due to the produced carbothermal reaction. As expected, the resulting electrical conductivity of these composites increased with the temperature and with the silicon content.

  5. siPRED: Predicting siRNA Efficacy Using Various Characteristic Methods

    Science.gov (United States)

    Pan, Wei-Jie; Chen, Chi-Wei; Chu, Yen-Wei

    2011-01-01

    Small interfering RNA (siRNA) has been used widely to induce gene silencing in cells. To predict the efficacy of an siRNA with respect to inhibition of its target mRNA, we developed a two layer system, siPRED, which is based on various characteristic methods in the first layer and fusion mechanisms in the second layer. Characteristic methods were constructed by support vector regression from three categories of characteristics, namely sequence, features, and rules. Fusion mechanisms considered combinations of characteristic methods in different categories and were implemented by support vector regression and neural networks to yield integrated methods. In siPRED, the prediction of siRNA efficacy through integrated methods was better than through any method that utilized only a single method. Moreover, the weighting of each characteristic method in the context of integrated methods was established by genetic algorithms so that the effect of each characteristic method could be revealed. Using a validation dataset, siPRED performed better than other predictive systems that used the scoring method, neural networks, or linear regression. Finally, siPRED can be improved to achieve a correlation coefficient of 0.777 when the threshold of the whole stacking energy is ≥−34.6 kcal/mol. siPRED is freely available on the web at http://predictor.nchu.edu.tw/siPRED. PMID:22102913

  6. Fabrication of Si/SiO2 Superlattice Microwire Array Solar Cells Using Microsphere Lithography

    Directory of Open Access Journals (Sweden)

    Shigeru Yamada

    2016-01-01

    Full Text Available A fabrication process for silicon/silicon dioxide (Si/SiO2 superlattice microwire array solar cells was developed. The Si/SiO2 superlattice microwire array was fabricated using a microsphere lithography process with polystyrene particles. The solar cell shows a photovoltaic effect and an open-circuit voltage of 128 mV was obtained. The limiting factors of the solar cell performance were investigated from the careful observations of the solar cell structures. We also investigated the influence of the microwire array structure on light trapping in the solar cells.

  7. Brazing of SiC using Cu-Si non reactive alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gasse, A.; Chaumat, G. [CEA Centre d`Etudes de Grenoble, 38 (France). Dept. d`Etudes des Materiaux; Rado, C.; Eustathopoulos, N. [Institut National Polytechnique, 38 - Grenoble (France)

    1995-12-31

    Wetting and adherence of filler metals on ceramics used to be achieved with active elements such as titanium. However, sessile drop experiments had already showed that a Cu 24 at % Si alloy has excellent wetting and adherence properties on SiC substrates under high vacuum without any measurable reactivity. Despite this good wetting, incomplete filling of joints was sometimes observed with such alloys in certain brazing experiments. This discrepancy is explained by a detailed analysis of Cu-Si alloy wetting mechanisms on SiC and confirmed by brazing experiments in different geometries. (authors). 8 figs.

  8. Expanding the Repertoire of Molecular Linkages to Silicon: Si-S, Si-Se, and Si-Te Bonds.

    Science.gov (United States)

    Hu, Minjia; Liu, Fenglin; Buriak, Jillian M

    2016-05-04

    Silicon is the foundation of the electronics industry and is now the basis for a myriad of new hybrid electronics applications, including sensing, silicon nanoparticle-based imaging and light emission, photonics, and applications in solar fuels, among others. From interfacing of biological materials to molecular electronics, the nature of the chemical bond plays important roles in electrical transport and can have profound effects on the electronics of the underlying silicon itself, affecting its work function, among other things. This work describes the chemistry to produce ≡Si-E bonds (E = S, Se, and Te) through very fast microwave heating (10-15 s) and direct thermal heating (hot plate, 2 min) through the reaction of hydrogen-terminated silicon surfaces with dialkyl or diaryl dichalcogenides. The chemistry produces surface-bound ≡Si-SR, ≡Si-SeR, and ≡Si-TeR groups. Although the interfacing of molecules through ≡Si-SR and ≡Si-SeR bonds is known, to the best of our knowledge, the heavier chalcogenide variant, ≡Si-TeR, has not been described previously. The identity of the surface groups was determined by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and depth profiling with time-of-flight-secondary ionization mass spectrometry (ToF-SIMS). Possible mechanisms are outlined, and the most likely, based upon parallels with well-established molecular literature, involve surface silyl radicals or dangling bonds that react with either the alkyl or aryl dichalcogenide directly, REER, or its homolysis product, the alkyl or aryl chalcogenyl radical, RE· (where E = S, Se, and Te).

  9. Spheroidization of Si in Al-12.6wt.%Si at eutectic temperature and its tensile properties

    Science.gov (United States)

    Jiaqing, Zhu; Ya, Liu; Haoping, Peng; Jianhua, Wang; Xuping, Su

    2017-10-01

    The morphology of Si affects significantly the mechanical properties of eutectic Al-Si alloy. In this letter, we report a novel method for the spheroidization of Si in eutectic Al-Si alloy. The results show that Si in eutectic Al-Si alloy could be spheroidized after annealing at eutectic temperature for 3 h. Si phase in the alloy exists in the form of ellipsoidal particles without faceted edges. The surface shape factor of Si phase is 0.8 and the average size of Si particles is only 3.3 µm. Compared with cast eutectic Al-Si alloy, the tensile strength and the hardness of the annealed alloy are decreased by 8.2% and 8.6%, respectively, but its elongation is increased by 79.4%. The fracture mode of Al-12.6%Si alloy annealed at 577 °C for 3 h belongs to ductile fracture.

  10. Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

    Directory of Open Access Journals (Sweden)

    Zhuk Sergey I.

    2017-01-01

    Full Text Available Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6, KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic voltammetry. Тhe electroreduction of Si(IV to metallic Si was observed as a single 4-electron wave under all considered conditions. The reactions of cathode reduction of silicon from fluoride and oxyfluoride complexes were suggested. It was shown that the process can be controlled by the preliminary transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current density on structure and morphology of silicon deposits obtained during galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.

  11. Evaluation of band offset at amorphous-Si/BaSi{sub 2} interfaces by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takabe, Ryota; Takeuchi, Hiroki; Du, Weijie; Toko, Kaoru; Suemasu, Takashi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Ito, Keita [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Japan Society for the Promotion of Science (JSPS), Chiyoda, Tokyo 102-0083 (Japan); Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Ueda, Shigenori [Synchrotron X-Ray Station at SPring-8, National Institute for Materials Science (NIMS), Sayo, Hyogo 679-5148 (Japan); Quantum Beam Unit, NIMS, Tsukuba, Ibaraki 305-0047 (Japan); Kimura, Akio [Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan)

    2016-04-28

    The 730 nm-thick undoped BaSi{sub 2} films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi{sub 2} and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi{sub 2} and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi{sub 2} is approximately −0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi{sub 2} layer under solar radiation could be selectively extracted through the a-Si/BaSi{sub 2} interface, promoting the carrier separation in the BaSi{sub 2} layer. We therefore conclude that the a-Si/BaSi{sub 2} interface is beneficial for BaSi{sub 2} solar cells.

  12. MARIO LUZI E L'ARTE: DA SIMONE AI CONTEMPORANEI

    African Journals Online (AJOL)

    User

    profonda alle cose che accadono, che si incontrano. [...] Ma c'è accanto questa natura sconvolgente dell'altra. Giovanna che in certe sue crisi fa a pezzi, mentalmente, tutta l'organizzazione di un mondo che anche Simone aveva condiviso; insomma, da lì si percepisce quanto sia abitato da forze avverse un universo, anche ...

  13. Optical properties investigation of [nc-Si:SiO{sub 2}/SiO{sub 2}]{sub 30} periodic multilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liang; Zhu, Jiang; Wei, Shenjin; Zhu, Huanfeng; Chen, Kun; Xu, Da [Fudan University, Department of Optical Science and Engineering, Shanghai (China); Li, Jing [Fudan University, Department of Optical Science and Engineering, Shanghai (China); Fudan University, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Shanghai (China)

    2012-11-15

    The optical properties of 30-layer [nc-Si:SiO{sub 2}/SiO{sub 2}]{sub 30} periodic films have been studied. The films were prepared by alternately evaporating SiO and SiO{sub 2} onto Si(100) substrates, followed by annealing at 1100 {sup circle} C. Spectroscopic ellipsometry spectrum analysis was used to determine the optical constants of the samples via the Forouhi-Bloomer model. The optical bandgap of a single periodic film is calculated. The photoluminescence (PL) spectra of three samples with different thicknesses clearly show that there are two physical origins of the PL process. (orig.)

  14. Electrospun a-Si using Liquid Silane/Polymer Inks

    Energy Technology Data Exchange (ETDEWEB)

    D.L. Schulz; J.M. Hoey; J. Smith; J. Lovaasen; C. Braun; X. Dai; K. Anderson; A. Elangovan; X. Wu; S. Payne; K. Pokhodnya; I. Akhatov; L. Pederson; P. Boudjouk

    2010-12-01

    Amorphous silicon nanowires (a-SiNWs) were prepared by electrospinning cyclohexasilane (Si{sub 6}H{sub 12}) admixed with polymethylmethacrylate (PMMA) in toluene. Raman spectroscopy characterization of these wires (d {approx} 50-2000 nm) shows 350 C treatment yields a-SiNWs. Porous a-SiNWs are obtained using a volatile polymer.

  15. A porous Si-emitter crystalline-Si solar cell with 18.97% efficiency

    Science.gov (United States)

    Wang, Liang-Xing; Zhou, Zhi-Quan; Hao, Hong-Chen; Lu, Ming

    2016-10-01

    A p-n junction was made on p-type Si wafer (15 × 15 × 0.2 mm3 in size) via phosphorous diffusion at 900 °C. Porous Si (PSi) with ultralow reflectivity (ultraviolet and visible regimes) was achieved by etching a Ag-coated n+ Si emitter in a solution of HF, H2O2 and H2O. The PSi was found to mainly consist of Si nanocrystallites with bandgap widths larger than that of bulk Si. Compared to other micro- or nanostructured Si-based crystalline-Si solar cells found in the literature, this PSi one possessed the feature of a graded band gap, which helped to suppress the surface recombination. In addition, the preparation method was readily applicable on large-scale-sized Si wafers. Also, the PSi acted as a down-shifter that absorbed the ultraviolet/violet light to which the Si solar cell responded poorly, and emitted a red one to which the cell responded well. Front and rear surface passivations were conducted by using SiO2 and Al2O3, respectively, to suppress the surface recombination and to facilitate the charge transfer. Indium-tin-oxide was used as the front electrode that was in good contact with the PSi, and Al was used as the rear one. For such a PSi-emitter crystalline-Si solar cell, enhancements of the photovoltaic responses from the ultraviolet to near-infrared regimes were observed; the open-circuit voltage was 606.8 mV, the short-circuit current density was 40.13 mA cm-2, the fill factor was 0.779 and the conversion efficiency was 18.97%.

  16. Diffusion of carbon oxides in SiO2 during SiC oxidation

    Science.gov (United States)

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi

    2013-03-01

    SiC is a wide-band-gap semiconductor and has an advantage to fabricate electronic devices such as MOSFETs due to the ability to thermally oxidize to SiO2. Despite many studies conducted on the oxidation of SiC, the kinetics such as diffusion and interface reaction is not fully understood. Here, we focus on the diffusion process during SiC oxidation, and clarify the diffusion mechanism of carbon oxides (CO and CO2) in SiO2 by means of density functional calculations. Our calculations demonstrate that the CO without any chemical bonds with host SiO2 is stabilized while the CO2 is incorporated between Si-O bonds of SiO2 to form a carbonate group. The energy of CO2 is found to be lower than that of CO by 3.7 eV, indicating that the most stable form of carbon oxides in SiO2 is CO2. Furthermore, the calculated energy barriers for diffusion of CO and CO2 are found to be 0.1 and 1.8 eV, respectively. These results thus imply that CO molecules easily react with oxidant such as O2 to form CO2 and the outward diffusion of resultant CO2 is rate-limiting. Indeed, the estimated activation energy for CO2 diffusion (3.5 eV) reasonably agrees with that for Si-face SiC (3.1 eV) obtained by Deal-Grove model considering product gas out-diffusion. This work was supported in part by Grant-in-Aid for Scientific Research (No. 24560025) from the Japan Society for the Promotion of Science.

  17. William Franke, Sulla verità poetica che è superiore alla Storia: Porfirio e la critica filosofica della letteratura William Franke, On the Poetic Truth that is Higher than History: Porphyry and the Philosophical Interpretation of Literature

    Directory of Open Access Journals (Sweden)

    Laura Lucia Rossi

    2010-06-01

    Full Text Available

    In this article we propose the translation of William Franke’s paper On the Poetic Truth that is Higher than History: Porphyry and the Philosophical Criticism of Literature, in which the American scholar presents the hermeneutic method of the ancient commentators of Homer, with particular reference to the critic practice applied by the Neoplatonic Porphyry in his De Antro Nympharum. With this treatment Franke proposes and hopes for the return to an interpretive method, called philosophical or speculative, also for contemporary criticism.

    In questo articolo è presentata la traduzione del saggio di William Franke Sulla verità poetica che è superiore alla Storia: Porfirio e la critica filosofica della letteratura, in cui lo studioso americano presenta il metodo ermeneutico degli antichi commentatori di Omero, con particolare riferimento alla critica praticata dal neoplatonico Porfirio, proponendo e auspicando il ritorno ad una modalità interpretativa, detta filosofica o speculativa, anche per la critica contemporanea.

  18. Analyse de l’effet du type de tâche sur l’évolution des connaissances à la suite d’un processus d’apprentissage collaboratif

    Directory of Open Access Journals (Sweden)

    Sabine Pohl

    2009-04-01

    Full Text Available L’article analyse l’effet du type de tâche sur le partage des connaissances à la suite d’un processus d’interaction dans un contexte d’apprentissage collaboratif. Cet apprentissage collaboratif est réalisé dans le cadre d’une formation universitaire. Deux types de tâches sont réalisés par les apprenants. Ils se distinguent selon que la solution nécessite ou non la confrontation de points de vue portant sur le champ conceptuel lié à l’apprentissage à réaliser. La méthode de collecte des données consiste en un entretien semi-directif. Les résultats montrent un effet du type de tâches sur l’évolution des connaissances partagées des apprenants.This longitudinal research analyses the effect of the type of task on the development of knowledge following an interaction process in a collaborative learning context. The framework for this collaborative learning is a university education. Two types of tasks are provided to the learners. They differ depending on whether or not the solution requires the comparison of points of view on the conceptual scope of what is to be learned. The data are collected through a semi-directive interview. The results show that the type of task has an effect on the development of shared knowledge.

  19. Microstructural evolution of SiC/Cu-Si composites obtained through reactive infiltration; Evolucion microestructural de composites SiC/aleaciones CuSi obtenidos a traves de infiltracion ractiva

    Energy Technology Data Exchange (ETDEWEB)

    Cornejo, J.; Ordonez, S.; Iturriza, I.

    2010-07-01

    The microstructural evolution of composites of SiC/Cu-Si alloys obtained through process of reactive infiltration to 1400 degree centigrade was studied. Three zones were detected in the obtained composites: the reaction zone, the transition zone and the infiltrated zone. In the reaction zone and transition zone the resulting microstructure was composed of a metallic phase, graphite laminae and SiC particles. It was found that SiC decomposes into these areas because of the alloy Cu-Si, so the available Si forms a liquid solution that a room temperature consisted of a a solid solution and a {gamma} phase (Cu{sub 5}Si). The carbon resulting from the decomposition of SiC precipitated as graphite laminae. In addition, the SiC decomposition was decreasing as the initial amount of Si in the alloy increased. (Author) 37 refs.

  20. Diffusion mobilities in the fcc{sub A}1 Cu-Si, Al-Si and Al-Cu-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Dachun [School of Mechanical Engineering, Xiangtan University, Xiangtan, Hunan Province 411105 (China); Liu, Ya [School of Materials Science and Engineering, Changzhou University, 1 Gehu Road, Changzhou, Jiangsu Province 213164 (China); Su, Xuping, E-mail: sxping@cczu.edu.cn [School of Mechanical Engineering, Xiangtan University, Xiangtan, Hunan Province 411105 (China); School of Materials Science and Engineering, Changzhou University, 1 Gehu Road, Changzhou, Jiangsu Province 213164 (China); Wang, Jianhua; Tu, Hao [School of Materials Science and Engineering, Changzhou University, 1 Gehu Road, Changzhou, Jiangsu Province 213164 (China); Huang, Jianfeng [School of Mechanical Engineering, Xiangtan University, Xiangtan, Hunan Province 411105 (China)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The atomic mobilities of fcc Cu-Si, Al-Si and Al-Cu-Si alloys have been assessed. Black-Right-Pointing-Pointer The calculated results agree well with various experimental diffusivities. Black-Right-Pointing-Pointer The temperature and concentration dependence are taken into consideration. Black-Right-Pointing-Pointer The mobility parameters obtained can be used to predict many diffusion phenomena. - Abstract: Based on the available thermodynamic parameters and experimental data of self-diffusivity, impurity diffusivity, intrinsic diffusivity, tracer diffusivity and interdiffusivity in the Cu-Si, Al-Si and Al-Cu-Si alloys, the atomic mobilities of Cu, Al and Si in face-centered cubic (fcc{sub A}1) Cu-Si, Al-Si and Al-Cu-Si alloys have been critically assessed as a function of temperature and composition using the CALPHAD-type and DICTRA software package. Comparisons between the calculated and measured coefficients reveal that most of the diffusivities can be reproduced satisfactorily. The obtained mobility parameters can be used to study diffusion-related characteristics for fcc{sub A}1 Cu-Si, Al-Si and Al-Cu-Si alloys.

  1. How to make the ionic Si-O bond more covalent and the Si-O-Si linkage a better acceptor for hydrogen bonding.

    Science.gov (United States)

    Grabowsky, Simon; Hesse, Maxie F; Paulmann, Carsten; Luger, Peter; Beckmann, Jens

    2009-05-18

    Variation of a bond angle can tune the reactivity of a chemical compound. To exemplify this concept, the nature of the siloxane linkage (Si-O-Si), the most abundant chemical bond in the earth's crust, was examined using theoretical calculations on the molecular model compounds H(3)SiOSiH(3), (H(3)Si)(2)OHOH, and (H(3)Si)(2)OHOSiH(3) and high-resolution synchrotron X-ray diffraction experiments on 5-dimethylhydroxysilyl-1,3-dihydro-1,1,3,3-tetramethyl-2,1,3-benzoxadisilole (1), a molecular compound that gives rise to the formation of very rare intermolecular hydrogen bonds between the silanol groups and the siloxane linkages. For theoretical calculations and experiment, electronic descriptors were derived from a topological analysis of the electron density (ED) distribution and the electron localization function (ELF). The topological analysis of an experimentally obtained ELF is a newly developed methodology. These descriptors reveal that the Si-O bond character and the basicity of the siloxane linkage strongly depend on the Si-O-Si angle. While the ionic bond character is dominant for Si-O bonds, covalent bond contributions become more significant and the basicity increases when the Si-O-Si angle is reduced from linearity to values near the tetrahedral angle. Thus, the existence of the exceptional intermolecular hydrogen bond observed for 1 can be explained by its very small strained Si-O-Si angle that adopts nearly a tetrahedral angle.

  2. Porous nC-Si/SiOx nanostructured layer on Si substrate with tunable photoluminescent properties fabricated by direct, precursor-free microplasma irradiation in air

    Science.gov (United States)

    Wang, Tao; Hu, Mingshan; Yang, Bin; Wang, Xiaolin; Liu, Jingquan

    2018-03-01

    Porous nC-Si/SiOx photoluminescent nanostructured layer is fabricated by direct, precursor-free microplasma irradiation on Si substrate in air. It is confirmed that the deposited layer has porous and cluster-like structures by scanning electron microscopy (SEM) and profile scanning. Fourier transform infrared transmission (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) results indicate the produced layer is actually composed of nanocrystalline silicon (nC-Si) embedded in SiOx matrix. Transmission electron microscopy (TEM) and Raman results show the mean particle size of nC-Si is mainly between 2 and 4 nm and the highest crystalline volume fraction reaches 86.9%. The photoluminescence (PL) measurement of nC-Si/SiOx layer exhibited a broad band centered at 1.7-1.9 eV, ranging from 1.2-2.4 eV, and could be tuned by varying the applied voltage. The synthetical mechanisms are discussed to explain the PL properties of the layers. We propose that the energetic ions bombing induced by high compressed electric field near the Si surface is the main reason for porous nC-Si/SiOx formation. Maskless deposition of the line pattern of nC-Si/SiOx layer was also successfully fabricated. This simple, maskless, vacuum-free and precursor-free technique could be used in various potential optoelectronics and biological applications in the future.

  3. Fluorescence enhancement of single DNA molecules confined in Si/SiO2 nanochannels

    DEFF Research Database (Denmark)

    Westerlund, F.; Persson, Karl Fredrik; Kristensen, Anders

    2010-01-01

    We demonstrate that the detected emission intensity from YOYO-labeled DNA molecules confined in 180 nm deep Si/SiO2 nano-funnels changes significantly and not monotonically with the width of the funnel. This effect may be of importance for quantitative fluorescence microscopy and for experiments...

  4. Green bean biofortification for Si through soilless cultivation: plant response and Si bioaccessibility in pods.

    Science.gov (United States)

    Montesano, Francesco Fabiano; D'Imperio, Massimiliano; Parente, Angelo; Cardinali, Angela; Renna, Massimiliano; Serio, Francesco

    2016-08-17

    Food plants biofortification for micronutrients is a tool for the nutritional value improvement of food. Soilless cultivation systems, with the optimal control of plant nutrition, represent a potential effective technique to increase the beneficial element content in plant tissues. Silicon (Si), which proper intake is recently recommended for its beneficial effects on bone health, presents good absorption in intestinal tract from green bean, a high-value vegetable crop. In this study we aimed to obtain Si biofortified green bean pods by using a Si-enriched nutrient solution in soilless system conditions, and to assess the influence of boiling and steaming cooking methods on Si content, color parameters and Si bioaccessibility (by using an in vitro digestion process) of pods. The Si concentration of pods was almost tripled as a result of the biofortification process, while the overall crop performance was not negatively influenced. The Si content of biofortified pods was higher than unbiofortified also after cooking, despite the cooking method used. Silicon bioaccessibility in cooked pods was more than tripled as a result of biofortification, while the process did not affect the visual quality of the product. Our results demonstrated that soilless cultivation can be successfully used for green bean Si biofortification.

  5. Atomic state and characterization of nitrogen at the SiC/SiO2 interface

    Science.gov (United States)

    Xu, Y.; Zhu, X.; Lee, H. D.; Xu, C.; Shubeita, S. M.; Ahyi, A. C.; Sharma, Y.; Williams, J. R.; Lu, W.; Ceesay, S.; Tuttle, B. R.; Wan, A.; Pantelides, S. T.; Gustafsson, T.; Garfunkel, E. L.; Feldman, L. C.

    2014-01-01

    We report on the concentration, chemical bonding, and etching behavior of N at the SiC(0001)/SiO2 interface using photoemission, ion scattering, and computational modeling. For standard NO processing of a SiC MOSFET, a sub-monolayer of nitrogen is found in a thin inter-layer between the substrate and the gate oxide (SiO2). Photoemission shows one main nitrogen related core-level peak with two broad, higher energy satellites. Comparison to theory indicates that the main peak is assigned to nitrogen bound with three silicon neighbors, with second nearest neighbors including carbon, nitrogen, and oxygen atoms. Surprisingly, N remains at the surface after the oxide was completely etched by a buffered HF solution. This is in striking contrast to the behavior of Si(100) undergoing the same etching process. We conclude that N is bound directly to the substrate SiC, or incorporated within the first layers of SiC, as opposed to bonding within the oxide network. These observations provide insights into the chemistry and function of N as an interface passivating additive in SiC MOSFETs.

  6. Thermographic Characterization of Impact Damage in SiC/SiC Composite Materials

    Science.gov (United States)

    Fox, Dennis S.; Cosgriff, Laura M.; Bhatt, Ramakrishna; Choi, Sung R.

    2005-01-01

    SiC/SiC composite materials targeted as turbine components for next-generation aero-engines are being investigated at NASA Glenn Research Center. In order to examine damage mechanisms in these materials, SiC/SiC coupons were impacted with 1.59 mm diameter steel spheres at increasing velocities from 115 m/s to 400 m/s. Pulsed thermography, a nondestructive evaluation technique that monitors the thermal response of a sample over time, was utilized to characterize the impact damage. A thermal standard of similar material was fabricated to aid in the interpretation of the thermographic data and to provide information regarding thermography system detection capabilities in 2.4 mm thick SiC/SiC composite materials. Flat bottom holes at various depths with aspect ratios greater than 2.5 were detectable in the thermal images. In addition, the edges of holes at depths of 1.93 mm into the sample were not as resolvable as flat bottom holes closer to the surface. Finally, cooling behavior was characterized in SiC/SiC materials and used to determine impact damage depth within an 8.5% error of a known depth.

  7. SiC-Si as a support material for oxygen evolution electrode in PEM steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Tomás García, Antonio Luis; Petrushina, Irina

    2011-01-01

    The need of higher energy efficiency in hydrogen production has promoted the research on improved catalysts for water electrolysis. In this work, a novel supported catalyst for oxygen evolution electrodes was prepared and characterized with different techniques. IrO2 supported on a SiC/Si composi...

  8. Computer aided cooling curve analysis for Al-5Si and Al-11Si alloys

    African Journals Online (AJOL)

    user

    The effect of grain refiner, modifier, and combination of grain refiner cum modifier was studied on Al-5Si and Al-11Si alloys using computer aided cooling curve analysis. For combined grain refinement and modification effect, Al-Ti-B-Sr single master alloy was developed that acted as both grain refiner and modifier.

  9. A Sensitive Optical Sensor Based on DNA Labeled Si@SiO 2 Core ...

    Indian Academy of Sciences (India)

    11

    A Sensitive Optical Sensor Based on DNA Labeled Si@SiO2 Core–Shell Nanoparticle for the Detection of Hg2+ ions in Environmental water samples. Krishnan Srinivasan1, Kathavarayan Subramanian1, Aruliah Rajasekar2, Kadarkarai Murugan3,. Giovanni Benelli4,5 and Kannaiyan Dinakaran6*. 1Department of ...

  10. Preparation of Si 3 N 4–SiC composites by microwave route

    Indian Academy of Sciences (India)

    Decrease in relative density has manifested in the reduction of fracture toughness and microhardness values of the composite with increase in SiC content although the good sintering of matrix Si3N4 limits the decrease of fracture toughness. Highest value of fracture toughness of 6.1 MPa m1/2 is observed in 10 vol.

  11. Current–voltage studies on β-FeSi2/Si heterojunction

    Indian Academy of Sciences (India)

    later treated by pulsed laser. Temperature of thermal annealing and diode area ... Silicide; semiconducting silicide; heterojunction; pulsed laser; I–V characteristics. 1. Introduction β-FeSi2 is a semiconducting silicide .... region and the electric field due to ionized impurities in Si yields a current in the opposite direction to that ...

  12. Structure of thin CrSi{sub 2} films on Si(0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Filonenko, O.; Falke, M.; Hortenbach, H.; Henning, A.; Beddies, G.; Hinneberg, H.-J

    2004-04-15

    The morphology and texture of CrSi{sub 2} films grown on Si(0 0 1) is reported. The films have been prepared under ultra high vacuum conditions by reactive codeposition and by the template method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed to investigate the influence of the substrate temperature and the template thickness on the silicide texture and morphology. XRD evidences that the major part of CrSi{sub 2} crystallites grows with an orientation of CrSi{sub 2}(0 0 1)[1 0 0] parallel Si(0 0 1)[1 1 0] within all present experiments. Considering the morphology and preferred orientation of the crystallites the substrate temperature of 700 deg. C is determined to be optimal for the codeposition growth method. A further improvement of the CrSi{sub 2}(0 0 1) texture and an increase of the grain size by an order of magnitude is observed after deposition of 0.5 nm Cr onto the Si(0 0 1) substrate at room temperature prior to the codeposition of Cr and Si at 700 deg. C.

  13. Weld microstructure in cast AlSi9/SiC(p metal matrix composites

    Directory of Open Access Journals (Sweden)

    J. Wysocki

    2009-04-01

    Full Text Available Welded joint in cast AlSi9/SiC/20(p metal matrix composite by manual TIG arc welding using AlMg5 filler metal has been described inhis paper. Cooling curves have been stated, and the influence in distribution of reinforced particles on crystallization and weldmicrostructure. Welded joint mechanical properties have been determined: hardness and tensile.

  14. Computer aided cooling curve analysis for Al-5Si and Al-11Si alloys ...

    African Journals Online (AJOL)

    The effect of grain refiner, modifier, and combination of grain refiner cum modifier was studied on Al-5Si and Al-11Si alloys using computer aided cooling curve analysis. For combined grain refinement and modification effect, Al-Ti-B-Sr single master alloy was developed that acted as both grain refiner and modifier.

  15. Proton conductivity and methanol permeability of Nafion-SiO2/SiWA composite membranes

    Science.gov (United States)

    Thiam, Hui San; Chia, Min Yan; Cheah, Qiao Rou; Koo, Charlene Chai Hoon; Lai, Soon Onn; Chong, Kok Chung

    2017-04-01

    Proton exchange membranes for a direct methanol fuel cell (DMFC) were prepared by incorporating silica/silicotungstic acid (SiO2/SiWA) inorganic composite into a Nafion polymer. The effects of SiO2/SiWA content on proton conductivity of membranes were investigated by using a four-probe conductivity cell. Methanol permeability of composite membrane was also determined by using a homemade diffusion cell and gas chromatography technique. It was found that proton conductivity of the composite membranes decreased with SiO2/SiWA content, however the highest proton conductivity achieved was 11% greater than the pure recast Nafion membrane. The methanol permeability of composite membrane was much lower than that of pure recast Nafion, in a reduction of 58% which indicated a better resistance to fuel crossover. Nafion-SiO2/SiWA composite membrane showed promising advantages over pure Nafion on electrochemical properties such as proton conductivity and fuel crossover and it is potentially attractive for use in DMFC.

  16. Direct observation of quantum confinement of Si nanocrystals in Si-rich nitrides

    Science.gov (United States)

    Nguyen, P. D.; Kepaptsoglou, D. M.; Ramasse, Q. M.; Olsen, A.

    2012-02-01

    The band gap of the active layers in stacked Si-based tandem solar cells can be fine tuned by changing the size of embedded silicon nanocrystals (Si NCs). Although SiO2 matrices have been predominantly used for such applications, nitride phases have recently emerged as a promising alternative. In this paper, we use high-resolution scanning transmission electron microscopy and energy-loss spectroscopy to report on the electronic structure of individual Si NCs embedded in silicon nitride films. Si NCs were produced by rf sputtering and exhibited controllable crystallite size and quality via different thermal annealing conditions. Quantum confinement effects were observed through a blue shift in both conduction band edges and volume plasmon energies as a function of particle size and structure. We show that, in good agreement with theoretical models, the volume plasmon energy Ep (eV) is related to the size d (nm) of Si NCs by Ep = 16.89+ 23.90/d2. Lattice distortion in twinned Si NCs and dangling bonds at defect centers are shown to be the cause of a weakening in quantum size effects and a reduction in the light emission efficiency of the films. Both electron spectroscopy and optical results are consistent in explaining the correlation between structure and optoelectronic properties of Si NCs.

  17. Fabrication and Characteristics of an nc-Si/c-Si Heterojunction MOSFETs Pressure Sensor

    Directory of Open Access Journals (Sweden)

    Xiaofeng Zhao

    2012-05-01

    Full Text Available A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances of the four nc-Si/c-Si heterojunction MOSFETs form a Wheatstone bridge. When the additional pressure is P, the nc-Si/c-Si heterojunction MOSFETs pressure sensor can measure this additional pressure P. The experimental results show that when the supply voltage is 3 V, length-width (L:W ratio is 2:1, and the silicon membrane thickness is 75 μm, the full scale output voltage of the pressure sensor is 15.50 mV at room temperature, and pressure sensitivity is 0.097 mV/kPa. When the supply voltage and L:W ratio are the same as the above, and the silicon membrane thickness is 45 μm, the full scale output voltage is 43.05 mV, and pressure sensitivity is 2.153 mV/kPa. Therefore, the sensor has higher sensitivity and good temperature characteristics compared to the traditional piezoresistive pressure sensor.

  18. Fabrication and characteristics of an nc-Si/c-Si heterojunction MOSFETs pressure sensor.

    Science.gov (United States)

    Zhao, Xiaofeng; Wen, Dianzhong; Li, Gang

    2012-01-01

    A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances of the four nc-Si/c-Si heterojunction MOSFETs form a Wheatstone bridge. When the additional pressure is P, the nc-Si/c-Si heterojunction MOSFETs pressure sensor can measure this additional pressure P. The experimental results show that when the supply voltage is 3 V, length-width (L:W) ratio is 2:1, and the silicon membrane thickness is 75 μm, the full scale output voltage of the pressure sensor is 15.50 mV at room temperature, and pressure sensitivity is 0.097 mV/kPa. When the supply voltage and L:W ratio are the same as the above, and the silicon membrane thickness is 45 μm, the full scale output voltage is 43.05 mV, and pressure sensitivity is 2.153 mV/kPa. Therefore, the sensor has higher sensitivity and good temperature characteristics compared to the traditional piezoresistive pressure sensor.

  19. Reactivity and wettability of SiC by Ni and Ni-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rado, C. [INPG, 38 - Saint Martin d`Heres (France). LTPCM; Kalogeropoulou, S. [INPG, 38 - Saint Martin d`Heres (France). LTPCM; Eustathopoulos, N. [INPG, 38 - Saint Martin d`Heres (France). LTPCM

    1996-08-01

    Wettability of SiC by Ni and Ni-Si alloys was studied at 1633K by the sessile drop technique under high vacuum or pure He. It is shown that reactivity in this system can be controlled and even nearly suppressed while obtaining good wetting and strong interface. (orig.)

  20. Progressive degradation in a-Si: H/SiN thin film transistors

    NARCIS (Netherlands)

    Merticaru, A.R.; Mouthaan, A.J.; Kuper, F.G.

    2003-01-01

    In this paper we present the study of gate-stress induced degradation in a-Si:H/SiN TFTs. The drain current transient during gate bias stress (forward or reverse bias) and subsequent relaxation cannot be fitted with the models existent in the literature but it shows to be described by a progressive

  1. Study of dynamics of charge trapping in a-Si:H/SiN TFTs

    NARCIS (Netherlands)

    Merticaru, A.R.; Mouthaan, A.J.; Kuper, F.G.

    2001-01-01

    In this paper we present the study of the failure mechanism responsible for long-term degradation that ultimately leads to instability in a-Si:H/SiN TFTs. The experimental data points we obtain by monitoring in-situ the drain current during gate bias stress (forward and reverse bias) and relaxation

  2. Si/SiGe heterointerfaces in one-, two-, and three-dimensional nanostructures: their impact on SiGe light emission

    Directory of Open Access Journals (Sweden)

    David J. Lockwood

    2016-03-01

    Full Text Available Fast optical interconnects together with an associated light emitter that are both compatible with conventional Si-based complementary metal-oxide- semiconductor (CMOS integrated circuit technology is an unavoidable requirement for the next-generation microprocessors and computers. Self-assembled Si/Si1-xGex nanostructures, which can emit light at wavelengths within the important optical communication wavelength range of 1.3 – 1.55 μm, are already compatible with standard CMOS practices. However, the expected long carrier radiative lifetimes observed to date in Si and Si/Si1-xGex nanostructures have prevented the attainment of efficient light-emitting devices including the desired lasers. Thus, the engineering of Si/Si1-xGex heterostructures having a controlled composition and sharp interfaces is crucial for producing the requisite fast and efficient photoluminescence (PL at energies in the range 0.8-0.9 eV. In this paper we assess how the nature of the interfaces between SiGe nanostructures and Si in heterostructures strongly affects carrier mobility and recombination for physical confinement in three dimensions (corresponding to the case of quantum dots, two dimensions (corresponding to quantum wires, and one dimension (corresponding to quantum wells. The interface sharpness is influenced by many factors such as growth conditions, strain, and thermal processing, which in practice can make it difficult to attain the ideal structures required. This is certainly the case for nanostructure confinement in one dimension. However, we demonstrate that axial Si/Ge nanowire (NW heterojunctions (HJs with a Si/Ge NW diameter in the range 50 – 120 nm produce a clear PL signal associated with band-to-band electron-hole recombination at the NW HJ that is attributed to a specific interfacial SiGe alloy composition. For three-dimensional confinement, the experiments outlined here show that two quite different Si1-xGex nanostructures incorporated into a Si

  3. SiGe growth on patterned Si(001) substrates : Surface evolution and evidence of modified island coarsening

    NARCIS (Netherlands)

    Zhang, J.J.; Stoffel, M.; Rastelli, A.; Schmidt, O.G.; Jovanovi?, V.; Nanver, L.K.; Bauer, G.

    2007-01-01

    The morphological evolution of both pits and SiGe islands on patterned Si(001) substrates is investigated. With increasing Si buffer layer thickness the patterned holes transform into multifaceted pits before evolving into inverted truncated pyramids. SiGe island formation and evolution are studied

  4. Synthesis and characterization of AlTiSiN/CrSiN multilayer coatings by cathodic arc ion-plating

    Science.gov (United States)

    Yang, B.; Tian, C. X.; Wan, Q.; Yan, S. J.; Liu, H. D.; Wang, R. Y.; Li, Z. G.; Chen, Y. M.; Fu, D. J.

    2014-09-01

    AlTiSiN/CrSiN multilayer coatings were deposited on Si (1 0 0) and cemented carbide substrates using Cr, AlTi cathodes and SiH4 gases by cathodic arc ion plating system. The influences of SiH4 gases flowrate on the structural and mechanical properties of the coatings were investigated, systematically. AlTiSiN/CrSiN coatings exhibit a B1 NaCl-type nano-multilayered structure in which the CrSiN nano-layers alternate with AlTiSiN nano-layers with multiple orientations of crystal planes indicated by XRD patterns and TEM. Si contents of the coatings increase with increasing SiH4 flowrate. The hardness of the coatings increases to the maximum value of 3500 Hv0.05 with increasing SiH4 flowrate from 20 to 40 sccm and then decreases with further addition of SiH4 gases. A higher adhesive force of 73 N is obtained at the flowrate of 48 sccm. The coatings exhibit different tribological performance when the mating materials were varied from Si3N4 to cemented carbide balls and the variation of friction coefficients of the coatings against Si3N4 influenced by SiH4 flowrate are not obvious as against cemented carbide balls.

  5. Realization of Colored Multicrystalline Silicon Solar Cells with SiO2/SiNx:H Double Layer Antireflection Coatings

    Directory of Open Access Journals (Sweden)

    Minghua Li

    2013-01-01

    Full Text Available We presented a method to use SiO2/SiNx:H double layer antireflection coatings (DARC on acid textures to fabricate colored multicrystalline silicon (mc-Si solar cells. Firstly, we modeled the perceived colors and short-circuit current density (Jsc as a function of SiNx:H thickness for single layer SiNx:H, and as a function of SiO2 thickness for the case of SiO2/SiNx:H (DARC with fixed SiNx:H (refractive index n=2.1 at 633 nm, and thickness = 80 nm. The simulation results show that it is possible to achieve various colors by adjusting the thickness of SiO2 to avoid significant optical losses. Therefore, we carried out the experiments by using electron beam (e-beam evaporation to deposit a layer of SiO2 over the standard SiNx:H for 156×156 mm2 mc-Si solar cells which were fabricated by a conventional process. Semisphere reflectivity over 300 nm to 1100 nm and I-V measurements were performed for grey yellow, purple, deep blue, and green cells. The efficiency of colored SiO2/SiNx:H DARC cells is comparable to that of standard SiNx:H light blue cells, which shows the potential of colored cells in industrial applications.

  6. Simulations of Proton Implantation in Silicon Carbide (SiC)

    Science.gov (United States)

    2016-03-31

    philip.feng@case.edu Abstract: We report on exploratory research effort with preliminary results on investigating fundamental radiation effects in...of implanting protons (hydrogen ions, H+) into SiC thin layers on silicon (Si) substrate, and explore the ion implantation conditions that are...create SiC-on-insulator (SiC-on-SiO2) films and structures [4,5]. It is important to understand and control the implantation depth. Presented here

  7. Synthesis of micro-sized interconnected Si-C composites

    Science.gov (United States)

    Wang, Donghai; Yi, Ran; Dai, Fang

    2016-02-23

    Embodiments provide a method of producing micro-sized Si--C composites or doped Si--C and Si alloy-C with interconnected nanoscle Si and C building blocks through converting commercially available SiO.sub.x (0

  8. Optical Diagnostics on HIT-SI3

    Science.gov (United States)

    Everson, Christopher; Jarboe, Thomas; Morgan, Kyle

    2016-10-01

    Interferometry and Thomson Scattering are implemented on the HIT-SI3 (Helicity Injected Torus - Steady Inductive 3) device to provide time resolved measurements of electron density and spatially resolved measurements of electron temperature, respectively. HIT-SI3 is a modification of the original HIT-SI apparatus that uses three injectors instead of two. The scientific aim of HIT-SI3 is to develop a deeper understanding of how injector behavior and interactions influence current drive and spheromak stability. The interferometer system makes use of an intermediate frequency between two parallel 184.3 μm Far-Infrared (FIR) laser cavities which are optically pumped by a CO2 laser. The phase shift in this beat frequency due to the plasma index of refraction is used to calculate the line-integrated electron density. To measure the electron temperature, Thomson Scattered light from a 20 J (1 GW pulse) Ruby laser off of free electrons in the HIT-SI3 plasma is measured simultaneously at four locations across the spheromak (nominally 23 cm minor radius). Polychromators bin the collected light into 3 spectral bands to detect the relative level of scattering. Work supported by the D.O.E.

  9. Formation and thermoelectric properties of Si/CrSi2/Si(001) heterostructures with stressed chromium disilicide nanocrystallites

    Science.gov (United States)

    Goroshko, Dmitry; Chusovitin, Evgeniy; Bezbabniy, Dmitry; Dózsa, Laszlo; Pécz, Bela; Galkin, Nikolay

    2015-05-01

    Three-layer heterostructures with embedded CrSi2 nanocrystallites were grown using molecular-beam epitaxy. The nanocrystallites have epitaxial orientation to the silicon lattice and are subjected to anisotropic compressive stress in the CrSi2 [001] direction. The thermoelectric power factor of the heterostructure is about 5 times higher than that in the substrate at 300-480 K. Taking into consideration the ratio of nanocomposite and substrate thickness, the real power factor is expected to be 2-3 orders higher than the measured one and it reaches 3200 μW K-2 m-1 at 470 K.[Figure not available: see fulltext.

  10. Carbon clusters as possible defects at the SiC-SiO2 interface

    Science.gov (United States)

    Liu, Yingdi; Dang, Hongli; Liu, Yang; Li, Ying; Chisholm, Matthew; Biggerstaff, Trinity; Duscher, Gerd; Wang, Sanwu

    2009-03-01

    High state densities in the band gap of the SiC-SiO2 interface significantly reduce the channel mobilities in SiC-based high-temperature/high-power microelectronics. Investigations of the nature of the interface defects are thus of great importance. While several possible defects including very small carbon clusters with up to four carbon atoms have been identified by first-principles theory, larger carbon clusters as possible defects have attracted less attention. Here, we report first-principles quantum-mechanical calculations for two larger carbon clusters, the C10 ring and the C20 fullerence, at the SiC-SiO2 interface. We find that both carbon clusters introduce significant states in the band gap. The states extend over the entire band gap with higher densities in the upper half of the gap, thus accounting for some of the interface trap densities observed experimentally.

  11. Relationship between 4H-SiC/SiO2 transition layer thickness and mobility

    Science.gov (United States)

    Biggerstaff, T. L.; Reynolds, C. L.; Zheleva, T.; Lelis, A.; Habersat, D.; Haney, S.; Ryu, S.-H.; Agarwal, A.; Duscher, G.

    2009-07-01

    The interfacial region between silicon carbide (SiC) and its native oxide contains a high density of interfacial traps, which is considered a major problem leading to a lower mobility that has hindered SiC metal oxide semiconductor field effect transistors from reaching their theoretical expectations. We investigate the microstructure and chemistry of the 4H-SiC/SiO2 interface due to variations in nitric oxide annealing and aluminum implantation using Z-contrast imaging and electron energy loss spectroscopy. A transition layer with a carbon to silicon ratio greater than 1 is consistently observed on the SiC side of the interface in each of these samples, and the width of this transition layer is found to be inversely related to the effective channel mobility measured on fabricated devices.

  12. Carbon Clusters as Possible Defects in the SiC-SiO2 Interface

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Hongli [ORNL; Ramkumar, Gudipati [unknown; Yang, Liu [unknown; Li, Ying [ORNL; Peterson, Heather [unknown; Chisholm, Matthew F [ORNL; Biggerstaff, Trinity Leigh [ORNL; Duscher, Gerd [University of Tennessee, Knoxville (UTK); Wang, Sanwu [ORNL

    2009-01-01

    High state densities in the band gap of the SiC-SiO2 interface significantly reduce the channel mobilities in SiC-based high-temperature/high-power microelectronics. Investigations of the nature of the interface defects are thus of great importance. While several possible defects including very small carbon clusters with up to four carbon atoms have been identified by first-principles theory, larger carbon clusters as possible defects have attracted less attention. Here, we report first-principles quantum-mechanical calculations for two larger carbon clusters, the C10 ring and the C20 fullerence, in the SiC-SiO2 interface. We find that both carbon clusters introduce significant states in the band gap. The states extend over the entire band gap with higher densities in the upper half of the gap, thus accounting for some of the interface trap densities observed experimentally

  13. On the compliant behaviour of free-standing Si nanostructures on Si(001) for Ge nanoheteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kozlowski, Grzegorz

    2012-04-24

    Selective chemical vapor deposition Ge heteroepitaxy approaches for high quality Ge nanostructure growth with reasonable thermal budget must be developed for local Ge photonic module integration. A promising vision is offered by the compliant substrate effects within nanometer scale Ge/Si heteroepitaxial structures. Here, in contrast to the classical Ge deposition on bulk Si substrates, the thermal and lattice mismatch strain energy accumulated in the Ge epilayer is partially shifted to the free-standing Si nanostructure. This strain partitioning phenomenon is at the very heart of the nanoheteroepitaxy theory (NHE) and, if strain energy levels are correctly balanced, offers the vision to grow defect-free nanostructures of lattice mismatched semiconductors on Si. In case of the Ge/Si heterosystem with a lattice mismatch of 4.2%, the strain partitioning phenomenon is expected to be triggered when free-standing Si nanopillars with the width of 50 nm and below are used. In order to experimentally verify NHE with its compliant substrate effects, a set of free-standing Ge/Si nanostructures with diameter ranging from 150 to 50 nm were fabricated and investigated. The main limitation corresponds to a simultaneous detection of (a) the strain partitioning phenomenon between Ge and Si and (b) the absence of defects on the nano-scale. In this respect, synchrotron-based grazing incidence X-ray diffraction was applied to study the epitaxial relationship, defect and strain characteristics with high resolution and sensitivity in a non-destructive way. Raman spectroscopy supported by finite element method calculations were used to investigate the strain distribution within a single Ge/Si nanostructure. Special focus was devoted to transmission electron microscopy to determine the quality of the Ge epilayer. It was found, that although high quality Ge nanoclusters can be achieved by thermal annealing on Si pillars bigger than 50 nm in width, no proof of strain partitioning

  14. Coadsorption of potassium and oxygen on thin β-FeSi2 overlayers on Si(111)

    Science.gov (United States)

    Kennou, S.; Tan, T. A. Nguyen

    1991-07-01

    We report UPS, AES and WF measurements on the interaction of K and O2 on thin semiconducting epitaxial layers of β-FeSi2 on Si(111). Oxygen was adsorbed on clean and K-covered β-FeSi2 at 300 K and the system was heated up to 900 K with the suicide remaining stable. A correlation of the experimental results indicates that at RT on clean β-FeSi2 oxygen chemisorbs dissociatively on silicon sites and does not interact with iron. In the presence of K oxygen chemisorbs on iron and on silicon sites with an increased sticking coefficient. No potassium oxide was formed. Upon heating up to 800 K SiO2 is formed on the suicide film under conditions in which the suicide remains stable.

  15. Joining of SiC[sub f]/SiC composites for thermonuclear fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Ferraris, M. (Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C. Duca degli Abruzzi 24, I-10129 Torino (Italy)); Badini, C. (Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C. Duca degli Abruzzi 24, I-10129 Torino (Italy)); Montorsi, M. (Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C. Duca degli Abruzzi 24, I-10129 Torino (Italy)); Appendino, P. (Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C. Duca degli Abruzzi 24, I-10129 Torino (Italy)); Scholz, H.W. (Institute for Advanced Materials, CEC Joint Research Centre, I-21020 Ispra (Vatican City State, Holy See) (Italy))

    1994-09-01

    Due to their favourable radiological behaviour, SiC[sub f]/SiC composites are promising structural materials for future use in fusion reactors. A problem to cope with is the joining of the ceramic composite material (CMC) to itself for more complex structures. Maintenance concepts for a reactor made of SiC[sub f]/SiC will demand a method of joining. The joining agents should comply with the low-activation approach of the base material. With the acceptable elements Si and Mg, sandwich structures of composite/metal/composite were prepared in Ar atmosphere at temperatures just above the melting points of the metals. Another promising route is the use of joining agents of boro-silicate glasses: their composition can be tailored to obtain softening temperatures of interest for fusion applications. The glassy joint can be easily ceramised to improve thermomechanical properties. The joining interfaces were investigated by SEM-EDS, XRD and mechanical tests. ((orig.))

  16. Formation of permeation barriers on ceramic SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Racault, C. [Commission of the European Communities, Ispra (Italy). Joint Research Centre; Serra, E. [Safety Technology Institute, Ispra Establishment, I-21020 Ispra (Vatican City State, Holy See) (Italy); Fenici, P. [Commission of the European Communities, Ispra (Italy). Joint Research Centre

    1996-10-01

    The effectiveness as permeation barriers of the following CVD and PVD (sputtering) coatings has been investigated: TiC+Al{sub 2}O{sub 3}(CVD), SiC(CVD), SiO{sub 2}(CVD), TiN(CVD), TiN(CVD)+TiN(PVD) and SiC(CVD)+Al{sub 2}O{sub 3}(PVD). The substrate material was a SiC/SiC composite, proposed as low activation structural material for fusion applications. Permeation measurements were performed in the temperature range 300-750 K using deuterium at pressures in the range 0.5-150 kPa. A linear dependence of permeation rate on pressure was measured. The efficiency of the coatings as deuterium permeation barriers is discussed in terms of coating microstructure. The best result was obtained with a bilayer of TiN(CVD) (15 {mu}m) +TiN(PVD) (8 {mu}m). (orig.).

  17. Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2002-01-01

    Full Text Available The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 in the mixture, silicide formation occurs also as a result of the reduction of silica by silicon and silicon carbide. The sintering of synthesized composite SiC-chromium silicides powders at a high temperature under a high pressure (T = 2073 K, P = 5 GPa is accompanied by the destruction of cc-SiC particles, the cc/3 transition in silicon carbide and deformation distortions of the lattices of chromium silicides.

  18. Preparation and low temperature properties of FeSi-type RuSi

    Energy Technology Data Exchange (ETDEWEB)

    Buschinger, B. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Geibel, C. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Diehl, J. [Augsburg Univ. (Germany). Lehrstuhl fuer Experimentalphysik 2; Weiden, M. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Guth, W. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik; Wildbrett, A. [Augsburg Univ. (Germany). Lehrstuhl fuer Experimentalphysik 2; Horn, S. [Augsburg Univ. (Germany). Lehrstuhl fuer Experimentalphysik 2; Steglich, F. [Technische Hochschule Darmstadt (Germany). Inst. fuer Festkoerperphysik

    1997-07-05

    We have reinvestigated the metallographic RuSi phase diagram and could establish the transition temperature from the low temperature FeSi-type to the high temperature CsCl-type structure for stoichiometric samples. Magnetic and transport properties of the low temperature modification in the temperature range 1.5 KSi-type RuSi is found to be semiconducting but still in the extrinsic regime at room temperature. Below 100 K, an additional gap opens and at temperatures <40 K variable-range hopping conduction sets in as the dominant transport mechanism. In contrast, resistivity measurements on CsCl-type RuSi show simple metallic behavior. (orig.)

  19. Synthesis of biomorphic SiC and SiO2 ceramics

    Directory of Open Access Journals (Sweden)

    ADELA EGELJA

    2008-07-01

    Full Text Available Coniferous wood (fir was transformed by pyrolysis into carbon preforms, which were subsequently converted into biomorphic ceramics by the pressure infiltration technique with colloidal silica. An in situ reaction between the silica and the carbon template occurred in the cellular wall at a high sintering temperature. Depending on the employed atmosphere, non-oxide (SiC or oxide (SiO2 ceramics were obtained. The morphology of the resulting porous ceramics and their phase composition were investigated by scanning electron microscopy (SEM/EDX and X-ray diffraction (XRD. The experimental results showed that the biomorphic cellular morphology of the wood maintained in both the SiC and silica ceramics, which consisted of only the b-SiC phase and SiO2, respectively.

  20. Blue-light emission from sputtered Si:SiO2 films without annealing

    Science.gov (United States)

    Hanaizumi, Osamu; Ono, Kazutaka; Ogawa, Yuichi

    2003-01-01

    We observed a photoluminescence (PL) spectrum at room temperature that had a peak with full width of half maximum (FWHM) of 0.38 eV near the band gap energy of 3.2 eV from a Si:SiO2 sputtered film without annealing. Blue-light emission could be seen by the naked eye. A low-intensity PL peak with FWHM of 0.20 eV was also observed at around 1.6 eV. We have already demonstrated that our method automatically forms Si clusters contributing to visible emission. Our results did not contradict the well-founded conjecture that there were two mechanisms of emission from Si clusters: emission at 1.6-1.7 eV due to the surface state of the oxidized Si nanocrystals and emission at the band gap energy originating from the quantum confinement effect.

  1. Si nanocrystals embedded in SiO2: Optical studies in the vacuum ultraviolet range

    DEFF Research Database (Denmark)

    Pankratov, V.; Osinniy, Viktor; Kotlov, A.

    2011-01-01

    Photoluminescence excitation and transmission spectra of Si nanocrystals of different diameters embedded in a SiO2 matrix have been investigated in the broad visible-vacuum ultraviolet spectral range using synchrotron radiation. The dependence of the photoluminescence excitation spectra...... on the nanocrystals size was experimentally established. It is shown that the photoluminescence excitation and absorption spectra are significantly blueshifted with decreasing Si nanocrystal size. A detailed comparison of photoluminescence excitation and absorption spectra with data from theoretical modeling has been...... done. It is demonstrated that the experimentally determined blueshift of the photoluminescence excitation and absorption spectra is larger than the theoretical predictions. The influence of point defects in the SiO2 matrix on the optical and luminescence properties of the embedded Si nanocrystals...

  2. Processing and properties of SiCf/SiBOC ceramic matrix composites by polyborosiloxane impregnation and pyrolysis

    Science.gov (United States)

    Vijay, Vipin; Prabhakaran, P. V.; Devasia, Renjith

    2013-06-01

    SiCf/SiBOC Ceramic Matrix Composites (CMCs) were fabricated using polyborosiloxane as the matrix resin and Nicalon™ NL-202 silicon carbide fiber as the reinforcement via polymer infiltration/impregnation and pyrolysis process (PIP). Repeated PIP cycles resulted in CMCs with a density value of ≈ 2 g/cc and a maximum average flexural strength value of 108 MPa. Oxidation resistance of SiCf/SiBOC was compared with Cf/C and Cf/SiBOC at 1000°C. SiCf/SiBOC composite shows a better oxidation resistance due to the formation of a protective layer of amorphous borosilicate glass on oxidation.

  3. Determination of band offsets in strained-Si heterolayers

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, C.K.; Samanta, S.K.; Chatterjee, S.; Dalapati, G.K.; Bhattacharya, S.; Armstrong, B.M.; Gamble, H.S.; McCarthy, J.; Perova, T.S.; Moore, R.A

    2004-09-01

    Strained-Si/SiGe/Si structures are of increasing importance for microelectronic applications. A fully relaxed-SiGe buffer layer is required for growing strained-Si for applications towards high performance field effect transistors (FETs) having strained-Si as the channel. Preparation of epitaxial strained-Si layers on relaxed-SiGe (001) heterostructures using low pressure chemical vapor deposition (LPCVD) is reported. Gas source molecular beam epitaxy (GSMBE) grown strained-Si films are used to compare with LPCVD strained-Si films. Characterization of the strained-Si layers has been performed using AFM, TEM and Raman spectroscopy. Conduction and valence band offsets of strained-Si on relaxed-SiGe heterostructures have been extracted from measured capacitance-voltage (C-V) profiling of MOS capacitors fabricated on strained-Si using SiO{sub 2} as the dielectric. Extracted experimental values of the valence and conduction band offsets are in good agreement with theoretical predictions.

  4. Carrier recombination in tailored multilayer Si/Si{sub 1−x}Ge{sub x} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Mala, S.A. [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Tsybeskov, L., E-mail: tsybesko@njit.edu [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Lockwood, D.J.; Wu, X.; Baribeau, J.-M. [National Research Council, Ottawa, ON, Canada KIA 0R6 (Canada)

    2014-11-15

    Photoluminescence (PL) measurements were performed in Si/Si{sub 1−x}Ge{sub x} nanostructures with a single Si{sub 0.92}Ge{sub 0.08} nanometer-thick layer incorporated into Si/Si{sub 0.6}Ge{sub 0.4} cluster multilayers. Under pulsed laser excitation, the PL decay associated with the Si{sub 0.92}Ge{sub 0.08} nano-layer is found to be nearly a 1000 times faster compared to that in Si/Si{sub 0.6}Ge{sub 0.4} cluster multilayers. A model considering Si/SiGe hetero-interface composition and explaining the fast and slow time-dependent recombination rates is proposed.

  5. Microhardness evaluation alloys Hf-Si-B; Avaliacao de microdureza de ligas Hf-Si-B

    Energy Technology Data Exchange (ETDEWEB)

    Gigolotti, Joao Carlos Janio; Costa, Eliane Fernandes Brasil [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Rocha, Elisa Gombio; Coelho, Gilberto Carvalho, E-mail: carlosjanio@uol.com.br, E-mail: eliane-costabrasi@hotmail.com, E-mail: cnunes@demar.eel.usp.br, E-mail: elisarocha@alunos.eel.usp.br, E-mail: coelho@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil)

    2014-08-15

    The technological advance has generated increasing demand for materials that can be used under high temperature, what includes intermetallic MR-Si-B (MR = refractory metal) alloys with multiphase structures, that can also be applied in oxide environments. Thus, this work had for objective the micro hardness study of the Hf-Si-B system alloys, heat treated at 1600 deg C, in the Hf rich region. Hf-Si-B alloys had been produced with blades of Hf (min. 99.8%), Si (min. 99.998%) and B (min. 99.5%), in the voltaic arc furnace and heat treated at 1600 deg C under argon atmosphere. The relationship of the phases had been previously identified by X-ray diffraction and contrast in backscattered electron imaging mode. The alloys had their hardness analyzed by method Vickers (micro hardness) with load of 0.05 kgf and 0.2 kgf and application time of 20 s. The results, obtained from the arithmetic mean of measurements for each alloy on the heterogeneous region, showed a mean hardness of 11.08 GPA, with small coefficient of variation of 3.8%. The borides HfB2 (19.34 GPa) e HfB - 11.76 GPa, showed the hardness higher than the silicides Hf2Si (8.57 GPa), Hf5Si3 (9.63 GPa), Hf3Si2 (11.66 GPa), Hf5Si4 (10.00 GPa), HfSi (10.02 GPa) e HfSi2 (8.61 GPa). (author)

  6. A DFT investigation on geometry and chemical bonding of isoelectronic Si8N6V-, Si8N6Cr, and Si8N6Mn+ clusters

    Science.gov (United States)

    Tam, Nguyen Minh; Pham, Hung Tan; Cuong, Ngo Tuan; Tung, Nguyen Thanh

    2017-10-01

    The geometric feature and chemical bonding of isoelectronic systems Si8N6Mq (M = V, Cr, Mn and q = -1, 0, 1, respectively) are investigated by means of density-functional-theory calculations. The encapsulated form is found for all ground-state structures, where the metal atom locates at the central site of the hollow Si8N6 cage. The Si8N6 cage is established by adding two Si atoms to a distorted Si6N6 prism, which is a combination of Si4N2 and Si2N4 strings. Chemical bonding of Si8N6Mq systems is explored by using the electron localization indicator and theory of atom in molecule, revealing the vital role of metal center in stabilizing the clusters.

  7. Computer simulation of CaSiO3 glass under compression: correlation between Si-Si pair radial distribution function and intermediate range order structure

    Science.gov (United States)

    Lan, Mai Thi; Thuy Duong, Tran; Iitaka, Toshiaki; Van Hong, Nguyen

    2017-06-01

    The structural organization of CaSiO3 glass at 600 K and under pressure of 0-100 GPa is investigated by molecular dynamics simulation (MDS). Results show that the atomic structure of CaSiO3 comprises SiO n and CaO m units considered as basic structural polyhedra. At low pressure, most of the basic structural polyhedra are SiO4, CaO5, CaO6 and CaO7. At high pressure most of the basic structural polyhedra are SiO5, SiO6 and CaO9, CaO10 and CaO11. The distribution of basic structural polyhedra is not uniform resulting in formation of Ca-rich and Si-rich regions. The distribution of SiO4, SiO5 and SiO6 polyhedra is also not uniform, but it tends to form SiO4-, SiO5-, and SiO6-clusters. For the Si-O network, under compression there is a gradual transition from the tetrahedral network (SiO4) to the octahedral network (SiO6) via SiO5 polyhedra. The SiO5-clusters are the same as immediate-phase in the transformation process. The size and shape of SiO4 tetrahedra change strongly under compression. While the size of SiO5 and SiO6 has also changed significantly, but the shape is almost unchanged under compression. The SiO n polyhedra can connect to each other via one common oxygen ion (corner-sharing bond), two common oxygen ions (edge-sharing bond) or three common oxygen ions (face-sharing bond). The Si-Si bond length in corner-sharing bonds is much longer than the ones in edge-sharing and face-sharing bonds. The change of intermediate range order (IRO) structure under compression relating to edge- and face-sharing bonds amongst SiO n at high pressure is the origin of the first peak splitting of the radial distribution functions of Si-Si pair. Under compression, the number of non-bridging oxygen (NBO) decreases. This makes the Si-O network more polymerized. At low pressure, most of the Ca2+ ions incorporate into the Si-O network via NBOs. At high pressure, the amount of NBO decreases, Ca2+ ions mainly incorporate into the Si-O network via bridging oxygen (BO) that

  8. Magnetism in nanocrystalline SiC films

    Science.gov (United States)

    Semenov, A. V.; Pashchenko, V. O.; Khirnyi, V. F.; Kozlovskyi, A. A.; Mateichenko, P. V.

    2015-11-01

    Magnetism been studied in two series of nanocrystalline SiC films obtained by the method of direct deposition of ions with an energy of ~100 eV at temperatures 1150 °C and 1200 C. There were separated the contributions of diamagnetism, paramagnetism and superparamagnetism+ferromagnetism. Magnetization value of the films correlates with the deposition temperature. In the films deposited at higher temperatures the value of magnetization was by 1.5 times lower. It was concluded that induced magnetism in nanocrystalline SiC films is caused by interaction of magnetic moments of neutral VSiVC divacancies in separate nanocrystals. The estimated concentration of neutral VSiVC divacancies in nanocrystalline SiC films is ~1020 cm-3.

  9. XXe/XXIe siècles

    OpenAIRE

    Allemand-Cosneau, Claude; Chassey, Éric de; Corbel, Laurence; d’Anthenaise, Claude; Grammont, Claudine; Huber, Thomas; Krebs, Sophie; Pelizzari, Maria Antonella; Popelard, Johan; Réra, Nathan; Salomé, Laurent; Soulages, Pierre; Tillier, Bertrand

    2014-01-01

    XXe siècle Pierre Soulages, regard sur l’histoire de l’art. Réflexions autour des pratiques de mixité entre art actuel et art ancien dans les musées... Qu’en est-il du fauvisme cent ans après ? Quels enjeux pour les recherches sur le caricatural au xxe siècle ? et XXIe siècle Le futurisme et ses acceptions, l’art de l’Entre-deux-guerres, les rapports conceptuels entre photographie et architecture, les éditions d’artistes depuis les années 1960, et l’art contemporain à l’épreuve de la destruc...

  10. Ultra high vacuum growth of CrSi2 and β-FeSi2 nanoislands and Si top layers on the plasma modified monocrystalline silicon surfaces

    Science.gov (United States)

    Galkin, Nikolay G.; Astashynski, Valiantsin M.; Chusovitin, Evgenii A.; Galkin, Konstantin N.; Dergacheva, Tatyana A.; Kuzmitski, Anton M.; Kostyukevich, Evgenii A.

    A set of silicon substrates processed by compression plasma was studied by means of atomic force microscopy (AFM). AFM data revealed a threshold nature (in terms of plasma flow energy) of the formation of tube-like surface structures (SS) observed as "waves" regardless of the conductivity type, resistivity, and the substrate orientation ((111) or (100)). For the first time nanoheterostructures Si(111)/NC CrSi2/Si and Si(100)/NC β-FeSi2 / Si have been formed on silicon substrates processed by compression plasma flow. Avery high density of CrSi2 nanoislands - (2-3)×1011 cm-2 was obtained for Cr-Si system but in the case of Fe-Si system the β-FeSi2 nanoislands density was only about 2×109 cm-2. According to the optical spectroscopy data during the process of silicon capping layer formation the CrSi2 and β-FeSi2 nanocrystals move up to the surface.

  11. SiC/Si heterojunction diodes fabricated by self-selective and by blanket rapid thermal chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yih, P.H.; Li, J.P.; Steckl, A.J. (Univ. of Cincinnati, OH (United States). Dept. of Electrical and Computer Engineering)

    1994-03-01

    SiC/Si heterojunction diodes have been fabricated by two different rapid thermal chemical vapor deposition (RTCVD) processes: a localized self-selective growth and blanket growth. The self-selective growth of crystalline cubic ([beta]) SiC was obtained by propane carbonization of the Si substrate in regions unprotected by an SiO[sub 2] layer, producing planar diodes. Mesa diodes were fabricated using the blanket growth of polycrystalline [beta]-SiC produced by the decomposition of methylsilane (CH[sub 3]SiH[sub 3]). The SiC/Si heterojunction diodes show good rectifying properties for both device structures. Reverse breakdown voltage of 50 V was obtained with the self-selective SiC/Si diode. The mesa diodes exhibited even higher breakdown voltages (V[sub br]) of 150 V and excellent ideality factors of 1.06 at 25 C. The high V[sub br] and good forward rectifying characteristics indicate that the SiC/Si heterojunction diode represents a promising approach for the fabrication of wide-gap emitter SiC/Si heterojunction bipolar transistors.

  12. Ag on Si(111) from basic science to application

    Energy Technology Data Exchange (ETDEWEB)

    Belianinov, Aleksey [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    In our work we revisit Ag and Au adsorbates on Si(111)-7x7, as well as experiment with a ternary system of Pentacene, Ag and Si(111). Of particular interest to us is the Si(111)-(√3x√3)R30°}–Ag (Ag-Si-√3 hereafter). In this thesis I systematically explore effects of Ag deposition on the Ag-Si-√3 at different temperatures, film thicknesses and deposition fluxes. The generated insight of the Ag system on the Si(111) is then applied to generate novel methods of nanostructuring and nanowire growth. I then extend our expertise to the Au system on the Ag-Si(111) to gain insight into Au-Si eutectic silicide formation. Finally we explore behavior and growth modes of an organic molecule on the Ag-Si interface.

  13. Generation of siRNA Nanosheets for Efficient RNA Interference

    Science.gov (United States)

    Kim, Hyejin; Lee, Jae Sung; Lee, Jong Bum

    2016-04-01

    After the discovery of small interference RNA (siRNA), nanostructured siRNA delivery systems have been introduced to achieve an efficient regulation of the target gene expression. Here we report a new siRNA-generating two dimensional nanostructure in a formation of nanosized sheet. Inspired by tunable mechanical and functional properties of the previously reported RNA membrane, siRNA nanosized sheets (siRNA-NS) with multiple Dicer cleavage sites were prepared. The siRNA-NS has two dimensional structure, providing a large surface area for Dicer to cleave the siRNA-NS for the generation of functional siRNAs. Furthermore, downregulation of the cellular target gene expression was achieved by delivery of siRNA-NS without chemical modification of RNA strands or conjugation to other substances.

  14. Characteristics of Al-Si-Mg Reinforced SiC Composites Produced by Stir Casting Route

    Science.gov (United States)

    Zulfia, A.; Zhakiah, T.; Dhaneswara, D.; Sutopo

    2017-05-01

    Al-Si-Mg alloy that is strengthened by silicon carbide particles has the potential to have excellent mechanical properties with light weight. In this study, metal matrix composites reinforced silicon carbide from 2 vf-% to 15 vf-% and magnesium amounted to 10 wt-% as an external dopant were fabricated by stir casting route. The magnesium was added to promote the wetting between Al matrix and reinforced SiC. The process involved SiC blended inside the molten Al by a stirrer with a rotational speed of 500 rpm at 800 °C for 2 minutes and degassed with Ar gas for 4 minutes to remove all of the gas content in the molten Al. The molten composite was then cast into the plate and tensile test sample molds. The effect of SiC addition on the mechanical properties and microstructure of the composites was investigated. The result showed that the optimum tensile strength was reached at 8 vf-% SiC with the value of 175 MPa, while the elongation was 9.1%. The maximum hardness and wear rate were achieved at 10 vf-% SiC with the values of 57 HRB and 0.0022 mm3/m, respectively. Such increase was related to the microstructures dominated by the presence of Chinese script, primary and eutectic Mg2Si which were contributed to the mechanical properties of the composites.

  15. Formation of ZnO nanostructures grown on Si and SiO2 substrates.

    Science.gov (United States)

    Lee, Seungjin; Park, Eunkyung; Lee, Jongtack; Park, Taehee; Lee, Sang-Hwa; Kim, Jae-Yong; Yi, Whikun

    2013-09-01

    ZnO nanorods are grown on Si-based substrate by chemical bath deposition method in aqueous solution using zinc nitrate hexahydrate. Various substrates having different surface morphology are used to evaluate their effect on growing ZnO nanorods, such as flat Si(100) wafer, small and large textured-Si wafer, porous silicon, flat SiO2 wafer, small and large textured-SiO2 wafer. The length, diameter, geometry, and coverage density of ZnO nanorods are investigated by field-emission scanning electron microscopy and summarized. SiO2 is a preferred substrate for the growth of ZnO nanorods to Si if the surface morphology of substrate is same, and the textured surface has much higher coverage density (> 95%) than the flat surface. Each nanorod is vertically grown along the c-axis on the top of each pyramid face for textured substrate, and forms the 3D sea sponge-like ZnO structure. The characteristics of ZnO nanorods grown on various substrates are analyzed by grazing-angle X-ray diffraction (XRD) and photoluminescence (PL) measurements.

  16. Fiber creep rate and high-temperature properties of SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Lewinsohn, C.A.; Jones, R.H.; Youngblood, G.E.; Henager, C.H. Jr. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Results of studies aimed at relating the fiber creep rate to the subcritical crack growth rate and fracture properties of SiC/SiC composites have demonstrated that the crack growth rate in a bulk composite is controlled by the fiber creep rate. This result was demonstrated for Nicalon-CG and Hi-Nicalon fiber reinforced material where a 50--75 c shift in the creep strength of the fiber resulted in a similar shift in the crack growth rate of the composite. Irradiation enhanced creep of SiC fibers and matrix must also be considered in the performance assessment of SiC/SiC composites. The shape of the displacement versus time curve for composites containing Hi-Nicalon fibers were similar to those of the previously tested materials, containing Ceramic-grade fibers, that exhibited subcritical crack growth controlled by time-dependent relaxation of the fiber-bridging stresses due to fiber creep. The crack velocity in the CG-C composites at 1100 C in argon was very close to that of the Hi-C materials at 1150--1175 C, this roughly corresponds to the temperature differential shown by DiCarlo et al. to obtain the same relaxation in 1 hour bend stress relaxation (BSR) tests in the two fibers. This supports the hypothesis that subcritical crack growth in SiC/SiC composites is controlled by fiber creep.

  17. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    Science.gov (United States)

    Bahrami, A.; Pech-Canul, M. I.; Gutiérrez, C. A.; Soltani, N.

    2015-12-01

    A study of the wetting behavior of three substrate types (SiC, SiO2-derived RHA and SiC/SiO2-derived RHA) by two Al-Si-Mg alloys using the sessile drop method has been conducted, using amorphous and crystalline SiO2 in the experiment. Mostly, there is a transition from non-wetting to wetting contact angles, being the lowest θ values achieved with the alloy of high Mg content in contact with amorphous SiO2. The observed wetting behavior is attributed to the deposited Mg on the substrates. A strong diffusion of Si from the SiC/Amorphous RHA substrate into the metal drop explains the free Si segregated at the drop/substrate interface and drop surface. Although incorporation of both SiO2-derived RHA structures into the SiC powder compact substrates increases the contact angles in comparison with the SiC substrate alone, the still observed acute contact angles in RHA/SiC substrates make them promising for fabrication of composites with high volume fraction of reinforcement by the pressureless infiltration technique. The observed wetting characteristics, with decrease in surface tension and contact angles is explained by surface related phenomena. Based on contact angle changes, drop dimensions and surface tension values, as well as on the interfacial elemental mapping, and XRD analysis of substrates, some wetting and reaction pathways are proposed and discussed.

  18. Thickness and temperature depending intermixing of SiO{sub x}/SiO{sub 2} and SiO{sub x}N{sub y}/SiO{sub 2} superlattices: Experimental observation and thermodynamic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Zhigunov, D. M. [Faculty of Physics, M. V. Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow (Russian Federation); Sarikov, A. [IMDEA Materials Institute, c/ Eric Kandel, 2, 28906 Getafe, Madrid (Spain); V. Lashkarev Institute of Semiconductor Physics NAS Ukraine, 45 Nauki Avenue, 03028 Kiev (Ukraine); Chesnokov, Yu. M.; Vasiliev, A. L. [National Research Centre “Kurchatov Institute”, pl. Akademika Kurchatova 1, 123182 Moscow (Russian Federation); Zakharov, N. [Max-Planck-Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Kashkarov, P. K. [Faculty of Physics, M. V. Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow (Russian Federation); National Research Centre “Kurchatov Institute”, pl. Akademika Kurchatova 1, 123182 Moscow (Russian Federation)

    2016-05-30

    Multilayered SiO{sub x}/SiO{sub 2} and SiO{sub x}N{sub y}/SiO{sub 2} thin films were fabricated using different techniques and subsequently annealed at high temperatures (≥1100 °C) in order to form Si nanocrystals by means of the well-known superlattice approach. The thickness of the SiO{sub x} and SiO{sub x}N{sub y} layers was varied from 1.5 to 5 nm, while for the SiO{sub 2} layers it was fixed at 4 nm. Using transmission electron microscopy, we showed that the multilayered structure generally sustains the high temperature annealing for both types of films. However, for samples with ultrathin SiO{sub x} or SiO{sub x}N{sub y} layers a breakdown of the superlattice structure and a complete intermixing of layers were observed at high temperatures. On the contrary, annealing at lower temperature (900 °C) preserves the multilayered structure even of such samples. Theoretical calculations showed that the intermixing of SiO{sub x}/SiO{sub 2} and SiO{sub x}N{sub y}/SiO{sub 2} superlattices in the ultrathin layers thickness limit may be explained thermodynamically by the gain in the Gibbs free energy, which depends in turn on the annealing temperature.

  19. Comparative Study of Thermal Shock Behavior with Fabrication Method of SiC{sub f}/SiC Composite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Hee; Park, Kwang Heon [Kyunghee University, Seoul (Korea, Republic of); Kim, Weon Ju; Park, Ji Yeon; Kim, Dae Jong; Lee, Hyeon Geun [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    An active search is ongoing for an alternative material to be used for manufacturing of nuclear fuel cladding. Studies are currently aimed at improving the safety of this cladding. In particular, ceramic-based nuclear fuel cladding, such as SiC, is receiving much attention due to the excellent radiation resistance, high strength, chemical durability against oxidation and corrosion, and excellent thermal conduction of ceramics. SiC{sub f}f/SiC composite cladding is required to maintain soundness against destruction and corrosion, and have excellent thermal conductivity to remove sufficiently the heat generated by nuclear fuel in output operation. For the reason, SiCf/SiC composite layers with densification are needed in SiC fiber bundle. As manufacturing methods to fill SiC matrix phase, there are Liquid Silicon Infiltration (LSI), Chemical Vapor Infiltration (CVI), Slurry Infiltration and Hot Pressure Sintering (SI-HPS), Polymer Infiltration and Pyrolysis (PIP), and Hybrid processes in combination of multiple processes (CVI+PIP, CVI{sub R}S and PIP+RS). This study conducted a comparison analysis, based on the manufacturing method, of the thermal shock behavior of metal cladding that had an SiC composite protective film added. The SiC{sub f}/SiC composite layer and the Zry-4 surface were separated, and cracks occurred in the SiC{sub f}/SiC composite. In the case of the cladding that had the SiC{sub f}/SiC composite protective film manufactured by the CVI process, there was no microcrack inside the SiC{sub f}/SiC composite. A microcracks that penetrated the fiber was observed inside the SiC{sub f}/SiC composite when it was manufactured using the PIP process; this was due to the absence of an interphase coating that increased the fracture toughness of the fiber.

  20. Si/Fe flux ratio influence on growth and physical properties of polycrystalline β-FeSi2 thin films on Si(100) surface

    Science.gov (United States)

    Tarasov, I. A.; Visotin, M. A.; Aleksandrovsky, A. S.; Kosyrev, N. N.; Yakovlev, I. A.; Molokeev, M. S.; Lukyanenko, A. V.; Krylov, A. S.; Fedorov, A. S.; Varnakov, S. N.; Ovchinnikov, S. G.

    2017-10-01

    This work investigates the Si/Fe flux ratio (2 and 0.34) influence on the growth of β-FeSi2 polycrystalline thin films on Si(100) substrate at 630 °C. Lattice deformations for the films obtained are confirmed by X-ray diffraction analysis (XRD). The volume unit cell deviation from that of β-FeSi2 single crystal are 1.99% and 1.1% for Si/Fe =2 and Si/Fe =0.34, respectively. Absorption measurements show that the indirect transition ( 0.704 eV) of the Si/Fe =0.34 sample changes to the direct transition with a bandgap value of 0.816 eV for the sample prepared at Si/Fe =2. The absorption spectrum of the Si/Fe =0.34 sample exhibits an additional peak located below the bandgap energy value with the absorption maximum of 0.36 eV. Surface magneto-optic Kerr effect (SMOKE) measurements detect the ferromagnetic behavior of the β-FeSi2 polycrystalline films grown at Si/Fe =0.34 at T=10 K, but no ferromagnetism was observed in the samples grown at Si/Fe =2. Theoretical calculations refute that the cell deformation can cause the emergence of magnetization and argue that the origin of the ferromagnetism, as well as the lower absorption peak, is β-FeSi2 stoichiometry deviations. Raman spectroscopy measurements evidence that the film obtained at Si/Fe flux ratio equal to 0.34 has the better crystallinity than the Si/Fe =2 sample.

  1. Production of NiSi phase by grain boundary diffusion induced solid state reaction between Ni{sub 2}Si and Si(1 0 0) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Shenouda, S.S., E-mail: shenouda_physics@yahoo.com [University of Debrecen, Department of Solid State Physics, H-4010, Debrecen, P.O. Box 2 (Hungary); Ain Shams University, Department of Physics, Faculty of Education, Roxy, Cairo (Egypt); Langer, G.A.; Katona, G.L.; Daróczi, L. [University of Debrecen, Department of Solid State Physics, H-4010, Debrecen, P.O. Box 2 (Hungary); Csik, A. [Institute Nuclear Research, Hungarian Academy of Sciences (ATOMKI), H-4001, Debrecen, P.O. Box 51 (Hungary); Beke, D.L. [University of Debrecen, Department of Solid State Physics, H-4010, Debrecen, P.O. Box 2 (Hungary)

    2014-11-30

    Graphical abstract: Sketch of grain boundary diffusion of Si (blue) into Ni{sub 2}Si film (yellow) forming NiSi (red). - Highlights: • New processing method for creation of homogeneous thin NiSi contacts from nanocrystalline-Ni{sub 2}Si/Si(1 0 0) substrate. • The NiSi forms by grain-boundary diffusion and reaction in a certain low temperature-time and thickness-time window. • The nucleated NiSi growths perpendicular to the grain boundaries and its velocity can also be determined. - Abstract: We report a process to obtain thin (5–20 nm thick) NiSi layers on Si(1 0 0) substrate from magnetron deposited Ni{sub 2}Si thin films at low temperatures (180–200°C). The time evolution of transformation was followed by means of Secondary Neutral Mass Spectrometry, transmission electron microscopy and resistance measurements. It is shown that there exist certain temperature-time and thickness-time windows inside of which the formation of NiSi takes place. The NiSi phase, formed along the grain boundaries of Ni{sub 2}Si and grew by the motion of these interfaces, gradually consumes the Ni{sub 2}Si phase. From the depth profiles of the first stage of the process, using the linear dependence of the average composition inside the film on the annealing time, the velocity of the grain boundary diffusion induced interface motion was also estimated. The normalized value of the resistance, proportional to the amount of the new phase, showed similar time evolution and yielded similar value for the interface velocity.

  2. Phytoextraction. A new pilot-plant project for the soil decontamination; Fitodecontaminazione. Un sistema pilota per la fito-decontaminazione di suoli inquinati da piombo

    Energy Technology Data Exchange (ETDEWEB)

    Bregante, M.; Paganetto, A.; Magistrelli, P.; Martella, L.; Gambale, F. [Consiglio Nazionale delle Ricerche, Istituto di Cibernetica e Biofisica, Genoa (Italy); Sacchi, G.A.; Rivetta, A.; Cocucci, R. [Milan Univ., Milan (Italy). Dipt. di Produzione Vegetale

    2001-12-01

    The environmental pollution is continuously increasing owing to anthropic activity. High concentrations of heavy metals may have drastic consequences on human health, particularly on children development. Conventional approaches have high economical and environmental costs that do not allow soil decontamination unless sites are particularly valuable. Phytoextraction uses plants producing biomass to transfer metals from the soil to the aerial parts of the plants at the expenses of solar energy. This work illustrates the activity performed within a Life-Environment european project in order to verify whether phytoremediation can be transferred from the laboratory scale to the field scale. [Italian] L'inquinamento del suolo dovuto all'accumulo di metalli come conseguenza delle attivita' umane sta continuamente e drammaticamente aumentando. Principali cause di contaminazione sono l'accumulo di rifiuti urbani, l'utilizzo di fertilizzanti, il traffico motorizzato, gli inceneritori, le centrali termoelettriche, le emissiioni industriali nocive, lo sfruttamento e dismissione di miniere. La decontaminazione di suoli inquinati da metalli e' un problema estremamente difficile da trattare. La bonifica di suoli inquinati da metalli mediante l'utilizzo di piante metallofite e/o agronomiche (fitoestrazione) emerge quindi come una tecnica estremamente interessante. Viene percio' illustrato il progetto PhyLeS (Phytoextraction of Lead from Soil), un progetto pilota finanziato dal programma Europeo Life/Ambiente (DG XI), che si propone di verficare i potenziali vantaggi e la trasferibilita' della metodica di fitoestrazione assistita dalla scala di laboratorio a quella di campo.

  3. Prefazione—aspetti relativi al benessere animale nel trasporto a lunga distanza

    Directory of Open Access Journals (Sweden)

    Gardner Murray

    2008-03-01

    veterinario e di sanità animale. Riconoscendone l'importanza, la World Organisation for Animal Health (Office International des Épizooties: OIE nel suo IV piano Strategico (punti a e b, ha identificato il benessere animale come tema chiave ed ha lanciato una serie di iniziative come lo sviluppo di linee guida per il benessere animale comuni per istruire i paesi, le industrie ed il pubblico in genere sulle pratiche più appropriate. Le risultanti linee guide dell'OIE per il trasporto di animali via mare e terra hanno fornito l'indispensabile punto di riferimento per ulteriori sviluppi futuri.Questo numero di Veterinaria Italiana si occupa di trasporto del bestiame. Non è una semplice collazione di articoli scientifici sull'argomento. Piuttosto, la sua unicità deriva dal fatto che fornisce un'indicazione e una guida sulle misure pratiche per migliorare l'approccio basato su dati scientifici. Politici, analisti del rischio, legislatori, manager della qualità, progettisti e formatori, avranno grandi vantaggi da questo numero, che servirà come documento di riferimento sull'argomento.Il ruolo dei veterinari e dei sevizi veterinari nel fornire guida ed indicazioni su benessere, sanità e allevamento di animali è fondamentale e non va sottovalutato. Essi hanno la grande responsabilità di occuparsi di questo argomento e grazie alle competenze acquisite, possono ‘fare la differenza’ nel supportare il continuo miglioramento del benessere e della sanità animale.

  4. Primary Crystals of AlfeMnSi Intermetallics in the Cast AlSi Alloys

    Directory of Open Access Journals (Sweden)

    Warmuzek M.

    2017-09-01

    Full Text Available In this paper the results of the microscopic observations of the intermetallic AlFeMnSi phases crystals formed in the liquid hypo- and eutectic AlSi alloys containing transition metals 3.0 wt.% Fe and 0.1, 0.5 and 2.0 wt.% Mn were presented. The crystals morphology has been revealed on both polished and deep etched microsections. The different stages of the primary AlFeMnSi phases particles formation in the solidifying alloy and their final morphology were shown as influenced by cooling rate and alloy chemical composition.

  5. Development of Readout Interconnections for the Si-W Calorimeter of SiD

    Energy Technology Data Exchange (ETDEWEB)

    Woods, M.; Fields, R.G.; Holbrook, B.; Lander, R.L.; Moskaleva, A.; Neher, C.; Pasner, J.; Tripathi, M.; /UC, Davis; Brau, J.E.; Frey, R.E.; Strom, D.; /Oregon U.; Breidenbach, M.; Freytag, D.; Haller, G.; Herbst, R.; Nelson, T.; /SLAC; Schier, S.; Schumm, B.; /UC, Santa Cruz

    2012-09-14

    The SiD collaboration is developing a Si-W sampling electromagnetic calorimeter, with anticipated application for the International Linear Collider. Assembling the modules for such a detector will involve special bonding technologies for the interconnections, especially for attaching a silicon detector wafer to a flex cable readout bus. We review the interconnect technologies involved, including oxidation removal processes, pad surface preparation, solder ball selection and placement, and bond quality assurance. Our results show that solder ball bonding is a promising technique for the Si-W ECAL, and unresolved issues are being addressed.

  6. Thermophysical and mechanical properties of SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Snead, L.L. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    The key thermophysical and mechanical properties for SiC/SiC composites are summarized, including temperature-dependent tensile properties, elastic constants, thermal conductivity, thermal expansion, and specific heat. The effects of neutron irradiation on the thermal conductivity and dimensional stability (volumetric swelling, creep) of SiC is discussed. The estimated lower and upper temperatures limits for structural applications in high power density fusion applications are 400 and 1000 C due to thermal conductivity degradation and void swelling considerations, respectively. Further data are needed to more accurately determine these estimated temperature limits.

  7. Development of readout interconnections for the Si-W calorimeter of SiD

    Science.gov (United States)

    Woods, M.; Fields, R. G.; Holbrook, B.; Lander, R. L.; Moskaleva, A.; Neher, C.; Pasner, J.; Tripathi, M.; Brau, J. E.; Frey, R. E.; Strom, D.; Breidenbach, M.; Freytag, D.; Haller, G.; Herbst, R.; Nelson, T.; Schier, S.; Schumm, B.

    2011-12-01

    The SiD collaboration is developing a Si-W sampling electromagnetic calorimeter, with anticipated application for the International Linear Collider. Assembling the modules for such a detector will involve special bonding technologies for the interconnections, especially for attaching a silicon detector wafer to a flex cable readout bus. We review the interconnect technologies involved, including oxidation removal processes, pad surface preparation, solder ball selection and placement, and bond quality assurance. Our results show that solder ball bonding is a promising technique for the Si-W ECAL, and unresolved issues are being addressed.

  8. Synthesis, characterization and luminescence of europium perchlorate with MABA-Si complex and coating structure SiO2@Eu(MABA-Si) luminescence nanoparticles.

    Science.gov (United States)

    Fu, Zhi-Fang; Li, Wen-Xian; Bai, Juan; Bao, Jin-Rong; Cao, Xiao-Fang; Zheng, Yu-Shan

    2017-05-01

    This article reports a novel category of coating structure SiO 2 @Eu(MABA-Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O was synthesized using HOOCC 6 H 4 N(CONH(CH 2 ) 3 Si(OCH 2 CH 3 ) 3 ) 2 (MABA-Si) and was used as a ligand. Furthermore, the as-prepared silica NPs were successfully coated with the -Si(OCH 2 CH 3 ) 3 group of MABA-Si to form Si-O-Si chemical bonds by means of the hydrolyzation of MABA-Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O. Coating structure SiO 2 @Eu(MABA-Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core-SiO 2 particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA-Si) was ~20 nm. In the binary complex Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O, the fluorescence spectra illustrated that the energy of the ligand MABA-Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO 2 @Eu(MABA-Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core-SiO 2 spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained. Copyright © 2016 John Wiley & Sons, Ltd.

  9. Chemical bonding and charge redistribution - Valence band and core level correlations for the Ni/Si, Pd/Si, and Pt/Si systems

    Science.gov (United States)

    Grunthaner, P. J.; Grunthaner, F. J.; Madhukar, A.

    1982-01-01

    Via a systematic study of the correlation between the core and valence level X-ray photoemission spectra, the nature of the chemical bonding and charge redistribution for bulk transition metal silicides has been examined. Particular emphasis is placed on Pt2Si and PtSi. It is observed that the strength of the metal (d)-silicon (p) interaction increases in the order Ni2Si, Pd2Si, Pt2Si. It is also observed that both the metal and silicon core lines shift to higher binding energy as the silicides are formed. The notion of charge redistribution for metallic bonds is invoked to explain these data.

  10. A declaration of independence for Mg/Si. [Al/Si intensity ratio predictive usefulness for Mg/Si intensity ratio in lunar X-ray fluorescence

    Science.gov (United States)

    Hubbard, N.; Keith, J. E.

    1978-01-01

    The weak covariation that exists between Al/Si and Mg/Si for large areas of the lunar surface is little, if any, stronger than that forced on a random set of numbers that are subject to closure. The Mg and Al variations implied by the Mg/Si and Al/Si intensity ratio data are qualitatively like those seen in lunar soil sample data. Two petrogenetic provinces are suggested for terra materials; one appears to have 50% higher Mg values than the other. Using the improved data, Mg/Si variations can be studied at a signal-to-noise ratio greater than 5/1.

  11. Liquinert quartz crucible for the growth of multicrystalline Si ingots

    OpenAIRE

    Fujiwara, Kozo; Horioka, Yukichi; Sakuragi, Shiro

    2017-01-01

    The growth of a multicrystalline silicon (mc-Si) ingot for solar cell applications was attempted using a Liquinert quartz crucible. A mc-Si ingot was also grown in a quartz crucible coated with Si3N4 powder for comparison with that from the Liquinert quartz crucible. The mc-Si ingot grown in the Liquinert quartz crucible had a shinier surface which has few impurity particles and higher minority carrier lifetime than the mc-Si ingot grown in a quartz crucible coated with Si3N4 powder. These re...

  12. Materials and devices for quantum information processing in Si/SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Sailer, Juergen

    2010-12-15

    In this thesis, we cover and discuss the complete way from material science, the fabrication of two-dimensional electron systems (2DES) in Si/SiGe heterostructures in molecular beam epitaxy (MBE), to quantum effects in few-electron devices based on these samples. We applied and compared two different approaches for the creation of pseudo-substrates that are as smooth, relaxed and defect free as possible. In the 'graded buffer' concept, starting from pure Si, the Ge content of the SiGe alloy is slowly and linearly increased until the desired Ge content is reached. In contrast, in the so-called 'low-temperature Si' concept, the SiGe alloy is deposited directly with the final Ge content, but onto a layer of highly defective Si. In terms of crystal defects, the 'graded buffer' turned out to be superior in comparison to the 'low-temperature Si' concept at the expense of a significantly higher material consumption. By continued optimization of the growth process, aiming at reducing the influence of the impurity, it nevertheless became possible to improve the charge carrier mobility from a mere 2000 cm{sup 2}/(Vs) to a record mobility exceeding 100 000 cm{sup 2}/(Vs). Within this work, we extended our MBE system with an electron beam evaporator for nuclear spin free {sup 28}Si. Together with the already existing effusion cell for {sup 70}Ge we were able to realize first 2DES in a nuclear spin free environment after successfully putting it to operation. The highest mobility 2DES in a nuclear spin free environment which have been realized in this thesis exhibited electron mobilities of up to 55 000 cm{sup 2}/(Vs). Quantum effects in Si/SiGe have been investigated in two- and zero-dimensional nanostructures. A remarkable phenomenon in the regime of the integer quantum Hall effect in Si/SiGe 2DES has been discovered and researched. For applications in quantum information processing and for the creation of qubits it is mandatory to

  13. $^{31}$Si Self-Diffusion in Si-Ge Alloys and Si-(B-)C-N Ceramics and Diffusion Studies for Al and Si Beam Developments

    CERN Multimedia

    Nylandsted larsen, A; Voss, T L; Strohm, A

    2002-01-01

    An invaluable method for studying diffusion in solids is the radiotracer technique. However, its applicability had been restricted to radiotracer atoms with half-lives $t_{1/2}$ of about 1~d or longer. Within the framework of IS372 a facility was developed in which short-lived radiotracer atoms ( 5min $\\scriptstyle{\\lesssim}$ $t_{1/2}\\scriptstyle{\\lesssim}$1 d ) can be used. For the implantation of the short-lived tracers the facility is flanged to the ISOLDE beamline, and all post-implantation steps required in the radiotracer technique are done in situ.\\\\ After successful application of this novel technique in diffusion studies of $^{11}$C ($t_{1/2}$ = 20.3 min), this experiment aims at performing self-diffusion studies of $^{31}$Si ($t_{1/2}$ = 2.6~h) in Si--Ge alloys and in amorphous Si--(B--)C--N ceramics.\\\\ Our motivation for measuring diffusion in Si--Ge alloys is their recent technological renaissance as well as the purpose to test the prediction that in these alloys the self-diffusion mechanism chang...

  14. Blistering behavior in Mo/Si multilayers

    NARCIS (Netherlands)

    Kuznetsov, Alexey; Gleeson, Michael; van de Kruijs, Robbert Wilhelmus Elisabeth; Bijkerk, Frederik; Kuznetsov, A.S.

    2011-01-01

    This paper is concerned with mapping the characteristics of blistering induced on Mo/Si multilayers as a result of irradiation by hydrogen species generated in a thermal capillary cracker. The nature and extent of the damage observed is dependent on exposure conditions such as the sample

  15. Universal Converter Using SiC

    Energy Technology Data Exchange (ETDEWEB)

    Dallas Marckx; Brian Ratliff; Amit Jain; Matthew Jones

    2007-01-01

    The grantee designed a high power (over 1MW) inverter for use in renewable and distributed energy systems, such as PV cells, fuel cells, variable speed wind turbines, micro turbines, variable speed gensets and various energy storage methods. The inverter uses 10,000V SiC power devices which enable the use of a straight-forward topology for medium voltage (4,160VAC) without the need to cascade devices or topologies as is done in all commercial, 4,160VAC inverters today. The use of medium voltage reduces the current by nearly an order of magnitude in all current carrying components of the energy system, thus reducing size and cost. The use of SiC not only enables medium voltage, but also the use of higher temperatures and switching frequencies, further reducing size and cost. In this project, the grantee addressed several technical issues that stand in the way of success. The two primary issues addressed are the determination of real heat losses in candidate SiC devices at elevated temperature and the development of high temperature packaging for SiC devices.

  16. A porous SiC ammonia sensor

    NARCIS (Netherlands)

    Connolly, E.J.; Timmer, B.H.; Pham, H.T.M.; Groeneweg, J.; Sarro, P.M.; Olthuis, Wouter; French, P.J.

    2005-01-01

    When used as the dielectric in a capacitive sensing arrangement, porous SiC has been found to be extremely sensitive to the presence of ammonia (NH3) gas. The exact sensing method is still not clear, but NH3 levels as low as 0.5 ppm could be detected. We report the fabrication and preliminary

  17. SiD Letter of Intent

    CERN Document Server

    Aihara, H.; Oreglia, M.; Berger, E.L.; Guarino, V.; Repond, J.; Weerts, H.; Xia, L.; Zhang, J.; Zhang, Q.; Srivastava, A.; Butler, J.M.; Goldstein, Joel; Velthuis, J.; Radeka, V.; Zhu, R.-Y.; Lutz, P.; de Roeck, A.; Elsener, K.; Gaddi, A.; Gerwig, H.; Grefe, C.; Klempt, W.; Linssen, L.; Schlatter, D.; Speckmayer, P.; Thom, J.; Yang, J.; Christian, D.C.; Cihangir, S.; Cooper, W.E.; Demarteau, M.; Fisk, H.E.; Garren, L.A.; Krempetz, K.; Kutschke, R.K.; Lipton, R.; Para, A.; Tschirhart, R.; Wenzel, H.; Yarema, R.; Grunewald, M.; Pankov, A.; U., Gomel State Tech.; Dutta, T.; Dauncey, P.D.; Balbuena, J.P.; Fleta, C.; Lozano, M.; Ullan, M.; Christian, G.B.; Faus-Golfe, A.; Fuster, J.; Lacasta, C.; Marinnas, C.; Vos, M.; Duarte, J.; Fernandez, M.; Gonzalez, J.; Jaramillo, R.; Lopez, Virto A.; Martinez-Eivero, C.; Moya, D.; Ruiz-Mimeno, A.; Vila, I.; Colledani, C.; Dorokhov, A.; Hu-Guo, C.; Winter, M.; Moortgat-Pick, G.; Onoprienko, D.V.; Kim, G.N.; Park, H.; Adloff, C.; Blaha, J.; Blaising, J.-J.; Cap, S.; Chefdeville, M.; Drancourt, C.; Espargiliare, A.; Gaglione, R.; Geffroy, N.; Jacquemier, J.; Karyotakis, Y.; Prast, J.; Vouters, G.; Gronberg, J.; Walston, S.; Wright, D.; Sawyer, L.; Laloum, M.; Ciobanu, C.; Chauveau, J.; Savoy-Navarro, A.; Andricek, L.; Moser, H.-G.; Cowan, R.f.; Fisher, P.; Yamamoto, R.K.; Kenney, ClMl; Boos, E.E.; Merkin, M.; Chen, S.; Chakraborty, D.; Dyshkant, A.; Hedin, D.; Zutshi, V.; Galkin, V.; D'Ascenzo, N.; Ossetski, D.; Saveliev, V.; Kapusta, F.; De Masi, R.; Vrba, V.; Lu, C.; McDonald, K.T.; Smith, A.J.S.; Bortoletto, D.; Coath, R.; Crooks, J.; Damerell, C.; Gibson, M.; Nichols, A.; Stanitzki, M.; Strube, J.; Turchetta, R.; Tyndel, M.; Weber, M.; Worm, S.; Zhang, Z.; Barklow, T.L.; Belymam, A.; Breidenbach, M.; Cassell, R.; Craddock, W.; Deaconu, C.; Dragone, A.; Graf, N.A.; Haller, G.; Herbst, R.; Hewett, J.L.; Jaros, J.A.; Johnson, A.S.; Kim, P.C.; MacFarlane, D.B.; Markiewicz, T.; Maruyama, T.; McCormick, J.; Moffeit, K.; Neal, H.A.; Nelson, T.K.; Oriunno, M.; Partridge, R.; Peskin, M.E.; Rizzo, T.G.; Rowson, P.; Su, D.; Woods, M.; Chakrabarti, S.; Dieguez, A.; Garrido, Ll.; Kaminski, J.; Conway, J.S.; Chertok, M.; Gunion, J.; Holbrook, B.; Lander, R.L.; Tripathi, S.M.; Fadeyev, V.; Schumm, B.A.; Oreglia, M.; Gill, J.; Nauenberg, U.; Oleinik, G.; Wagner, S.R.; Ranjan, K.; Shivpuri, R.; Varner, G.S.; Orava, R.; Van Kooten, R.; Bilki, B.; Charles, M.; Kim, T.J.; Mallik, U.; Norbeck, E.; Onel, Y.; Brau, B.P.; Willocq, S.; Taylor, G.N.; Riles, Keith; Yang, H.-J.; Kriske, R.; Cremaldi, L.; Rahmat, R.; Lastovicka-Medin, G.; Seidel, S.; Hildreth, M.D.; Wayne, M.; Brau, J.E.; Frey, R.; Sinev, N.; Strom, D.M.; Torrence, E.; Banda, Y.; Burrows, P.N.; Devetak, E.; Foster, B.; Lastovicka, T.; Li, Y.-M.; Nomerotski, A.; Riera-Babures, J.; Vilasis-Cardona, X.; Manly, S.; Adeva, B.; Iglesias Escudero, C.; Vazquez Regueiro, P.; Saborido Silva, J.J.; Gallas Torreira, A.; Gao, D.; Jie, W.; Jungfeng, Y.; Li, C.; Liu, S.; Liu, Y.; Sun, Y.; Wang, Q.; Yi, J.; Yonggang, W.; Zhao, Z.; De, K.; Farbin, A.; Park, S.; Smith, J.; White, A.P.; Yu, J.; Lou, X.C.; Abe, T.; Iwasaki, M.; Lubatti, H.J.; Band, H.R.; Feyzi, F.; Prepost, R.; Karchin, P.E.; Milstene, C.; Baltay, C.; Dhawan, S.; Kwon, Y.-J.

    2009-01-01

    Letter of intent describing SiD (Silicon Detector) for consideration by the International Linear Collider IDAG panel. This detector concept is founded on the use of silicon detectors for vertexing, tracking, and electromagnetic calorimetry. The detector has been cost-optimized as a general-purpose detector for a 500 GeV electron-positron linear collider.

  18. siRNA for Influenza Therapy

    Directory of Open Access Journals (Sweden)

    Sailen Barik

    2010-07-01

    Full Text Available Influenza virus is one of the most prevalent and ancient infections in humans. About a fifth of world's population is infected by influenza virus annually, leading to high morbidity and mortality, particularly in infants, the elderly and the immunocompromised. In the US alone, influenza outbreaks lead to roughly 30,000 deaths each year. Current vaccines and anti-influenza drugs are of limited use due to high mutation rate of the virus and side effects. In recent years, RNA interference, triggered by synthetic short interfering RNA (siRNA, has rapidly evolved as a potent antiviral regimen. Properly designed siRNAs have been shown to function as potent inhibitors of influenza virus replication. The siRNAs outperform traditional small molecule antivirals in a number of areas, such as ease of design, modest cost, and fast turnaround. Although specificity and tissue delivery remain major bottlenecks in the clinical applications of RNAi in general, intranasal application of siRNA against respiratory viruses including, but not limited to influenza virus, has experienced significant success and optimism, which is reviewed here.

  19. siRNA for Influenza Therapy.

    Science.gov (United States)

    Barik, Sailen

    2010-07-01

    Influenza virus is one of the most prevalent and ancient infections in humans. About a fifth of world's population is infected by influenza virus annually, leading to high morbidity and mortality, particularly in infants, the elderly and the immunocompromised. In the US alone, influenza outbreaks lead to roughly 30,000 deaths each year. Current vaccines and anti-influenza drugs are of limited use due to high mutation rate of the virus and side effects. In recent years, RNA interference, triggered by synthetic short interfering RNA (siRNA), has rapidly evolved as a potent antiviral regimen. Properly designed siRNAs have been shown to function as potent inhibitors of influenza virus replication. The siRNAs outperform traditional small molecule antivirals in a number of areas, such as ease of design, modest cost, and fast turnaround. Although specificity and tissue delivery remain major bottlenecks in the clinical applications of RNAi in general, intranasal application of siRNA against respiratory viruses including, but not limited to influenza virus, has experienced significant success and optimism, which is reviewed here.

  20. Si diffusion in GaAs

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Theoretical studies are carried out to ascertain the dominant mechanism of Si diffusion in GaAs. Lattice dynamical model calculations have shown that the most probable diffusion mechanism is through a single vacancy even though several experiments cannot fix the mechanism as substitutional, substitutional–.

  1. Ordering of vacancies on Si(001)

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.

    1997-01-01

    Missing dimer vacancies are always present on the clean Si(001) surface. The vacancy density can be increased by ion bombardment (Xe+, Ar+), etching (O2, Br2, I2, etc.) or Ni contamination. The equilibrium shape at low vacancy concentrations (<0.2¿0.3 monolayers) of these vacancy islands is

  2. Design of lentivirally expressed siRNAs

    NARCIS (Netherlands)

    Liu, Ying Poi; Berkhout, Ben

    2013-01-01

    RNA interference (RNAi) has been widely used as a tool for gene knockdown in fundamental research and for the development of new RNA-based therapeutics. The RNAi pathway is typically induced by expression of ∼22 base pair (bp) small interfering RNAs (siRNAs), which can be transfected into cells. For

  3. Shape modification of Si nanowires by using faceted silicide catalysts nucleated in Au-Si catalyst solution during the growth

    Directory of Open Access Journals (Sweden)

    Erchao Meng

    2013-09-01

    Full Text Available The shape modification of Si nanowires is demonstrated using faceted solid silicide catalysts. The Si nanowires were grown on Si(111 substrates covered with Au as a catalyst using MnCl2 and Si powders as source materials. The solid silicide catalysts were nucleated and formed in the Au-Si catalyst solution at the top of the nanowires during the growth. The faceted solid silicides grew larger with increased growth time and played a role as a solid catalyst. The faceted shape of the catalyst defines the shape of the faceted Si nanowire. The squared Si nanowires were grown with the growth direction of Si[111] and the sidewalls of {110} and {211} planes. The growth evolution of the faceted Si nanowires occurs by a vapor-liquid-solid mechanism followed by the silicide vapor-solid-solid mechanism.

  4. Band gap tuning in Si-SiO2 nanocomposite: Interplay of confinement effect and surface/interface bonding

    Science.gov (United States)

    Rani, Ekta; Ingale, Alka; Phase, D. M.; Chaturvedi, A.; Mukherjee, C.; Joshi, M. P.; Kukreja, L. M.

    2017-12-01

    Correlation between size, bonding of Si and O at the surface/interface of Si nanocrystals and frequency of Si phonons in Si-SiO2 nanocomposites is established using Raman mapping and X-ray photoelectron spectroscopy. Corroboration of these results with absorption spectroscopy shows that lowering of direct transition of light electron conduction band to heavy hole valence band ∼2.8 and 2.95 eV is a result of the interplay between effect of electron confinement (increases band gap) and oxidation bonding environment at the surface/interface (decreases band gap) of a nanocrystal in Si-SiO2 nanocomposites. These studies have generated deeper insight into the fundamental understanding of the nanocomposite, which can allow easy optical microscopy monitoring of Si-SiO2 based device fabrication.

  5. Effects of laser-induced quenching and restoration of photoluminescence in hybrid Si/SiOx nanoparticles

    Science.gov (United States)

    Bagratashvili, V. N.; Dorofeev, S. G.; Ischenko, A. A.; Kononov, N. N.; Panchenko, V. Ya; Rybaltovskii, A. O.; Sviridov, A. P.; Senkov, S. N.; Tsypina, S. I.; Yusupov, V. I.; Yuvchenko, S. A.; Zimnyakov, D. A.

    2013-09-01

    We studied the processes of pulsed and continuous-wave (CW) laser excitation of photoluminescence (PL) in nc-Si/SiOx nanoparticles. CW laser irradiation of the nc-Si/SiOx sol in dimethylsulfoxide (DMSO) and in a thin film was found to quench PL with an essentially nonexponential dynamics. The laser-induced variation of the Rayleigh scattering signal from the nc-Si/SiOx sol in DMSO was found to replicate that of the PL quenching. The IR and Raman spectra of the laser-exposed nc-Si/SiOx exhibited no new bands that could be evidence of their chemical transformations. There were also no perceptible effects pointing to laser-induced aggregation of the nc-Si/SiOx particles in the sol. 355 nm pulse-periodic laser irradiation of the nc-Si/SiOx particles preliminarily exposed to a 405 nm CW laser (which causes a strong PL quenching effect) was found to result in a rapid restoration of the original PL signal, which means that the effect of laser quenching of PL can be entirely reversible. We considered a mechanism of the reversible photosensitivity of nc-Si/SiOx, based on the processes of ionization of the photoluminescent oxygen-deficient centers in their suboxide shell and electron capture by traps, followed by their laser-assisted photorecombination.

  6. Purity and radioactive decay behaviour of industrial 2D-reinforced SiC[sub f]/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, H.W. (Institute for Advanced Materials, CEC Joint Research Centre, I-21020 Ispra (Vatican City State, Holy See) (Italy)); Zucchetti, M. (Dipartimento di Energetica, Politecnico di Torino, C. Duca degli Abruzzi 24, I-10129 Torino (Italy)); Casteleyn, K. (Institute for Advanced Materials, CEC Joint Research Centre, I-21020 Ispra (Vatican City State, Holy See) (Italy)); Adelhelm, C. (IMF I, Kernforschungszentrum Karlsruhe GmbH, Postfach 3640, D-76344 Karlsruhe (Germany))

    1994-09-01

    Ceramic matrix composites based on SiC with continuous fibres (SiC[sub f]/SiC) are considered promising structural materials for future fusion devices. It was still to clarify, whether impurities in industrial SiC[sub f]/SiC could jeopardise radiological advantages. Experimental impurity analyses revealed a two-dimensionally reinforced SiC[sub f]/SiC with the matrix produced by CVI as very pure. Chemo-spectrometric methods were combined with radioactivation methods (CPAA, NAA). A quantification of the main constituents Si, C and O was added. Calculations with the FISPACT-2.4 code and EAF-2 library identified elements detrimental for different low-activation criteria. For the neutron exposure, EEF reactor-study first wall and blanket conditions were simulated. The calculated SiC[sub f]/SiC included 48 trace elements. Even under conservative assumptions, all low-activation limits of European interest are fulfilled. Exclusively the hands-on recycling limit for the First Wall can intrinsically not be satisfied with SiC. The theoretical goal of a SiC[sub f]/SiC depleted of [sup 28]Si (isotopic tailoring) is critically discussed. ((orig.))

  7. New Insights into Understanding Irreversible and Reversible Lithium Storage within SiOC and SiCN Ceramics

    Directory of Open Access Journals (Sweden)

    Magdalena Graczyk-Zajac

    2015-02-01

    Full Text Available Within this work we define structural properties of the silicon carbonitride (SiCN and silicon oxycarbide (SiOC ceramics which determine the reversible and irreversible lithium storage capacities, long cycling stability and define the major differences in the lithium storage in SiCN and SiOC. For both ceramics, we correlate the first cycle lithiation or delithiation capacity and cycling stability with the amount of SiCN/SiOC matrix or free carbon phase, respectively. The first cycle lithiation and delithiation capacities of SiOC materials do not depend on the amount of free carbon, while for SiCN the capacity increases with the amount of carbon to reach a threshold value at ~50% of carbon phase. Replacing oxygen with nitrogen renders the mixed bond Si-tetrahedra unable to sequester lithium. Lithium is more attracted by oxygen in the SiOC network due to the more ionic character of Si-O bonds. This brings about very high initial lithiation capacities, even at low carbon content. If oxygen is replaced by nitrogen, the ceramic network becomes less attractive for lithium ions due to the more covalent character of Si-N bonds and lower electron density on the nitrogen atom. This explains the significant difference in electrochemical behavior which is observed for carbon-poor SiCN and SiOC materials.

  8. Electrical behavior of MIS devices based on Si nanoclusters embedded in SiOxNy and SiO2 films

    Directory of Open Access Journals (Sweden)

    Debieu Olivier

    2011-01-01

    Full Text Available Abstract We examined and compared the electrical properties of silica (SiO2 and silicon oxynitride (SiOxNy layers embedding silicon nanoclusters (Sinc integrated in metal-insulator-semiconductor (MIS devices. The technique used for the deposition of such layers is the reactive magnetron sputtering of a pure SiO2 target under a mixture of hydrogen/argon plasma in which nitrogen is incorporated in the case of SiOxNy layer. Al/SiOxNy-Sinc/p-Si and Al/SiO2-Sinc/p-Si devices were fabricated and electrically characterized. Results showed a high rectification ratio (>104 for the SiOxNy-based device and a resistive behavior when nitrogen was not incorporating (SiO2-based device. For rectifier devices, the ideality factor depends on the SiOxNy layer thickness. The conduction mechanisms of both MIS diode structures were studied by analyzing thermal and bias dependences of the carriers transport in relation with the nitrogen content.

  9. Synthesis of SiC decorated carbonaceous nanorods and its hierarchical composites Si@SiC@C for high-performance lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chundong [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Li, Yi, E-mail: liyi@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou (China); Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Ostrikov, Kostya [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4000 (Australia); Plasma Nanoscience, Industrial Innovation Program, CSIRO Manufacturing Flagship, Lindfield, New South Wales 2070 (Australia); Yang, Yonggang [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou (China); Zhang, Wenjun, E-mail: apwjzh@cityu.edu.hk [Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China)

    2015-10-15

    SiC- based nanomaterials possess superior electric, thermal and mechanical properties. However, due to the tricky synthesis process, which needs to be carried out under high temperature with multi-step reaction procedures, the further application is dramatically limited. Herein, a simple as well as a controllable approach is proposed for synthesis of SiC- based nanostructures under low temperature. Phenyl-bridged polysilsesquioxane was chosen as the starting material to react with magnesium at 650 °C, following which SiC@C nanocomposites were finally obtained, and it maintains the original bent rod-like architecture of polysilsesquioxanes. The possible formation process for the nanocomposites can proposed as well. The electrochemical behaviour of nanocomposites was accessed, verifying that the synthesized SiC@C nanocomposites deliver good electrochemical performance. Moreover, SiC@C also shows to be a promising scaffold in supporting Si thin film electrode in achieving stable cycling performance in lithium ion batteries. - Highlights: • SiC@C bent nanorods were synthesized with a magnesium reaction approach. • Carbon nanorod spines studded with ultrafine β-SiC nanocrystallines was realized. • The synthesized SiC@C keeps the original rod-like structure of polysilsesquioxanes. • The possible formation process for the nanocomposites was analysed and proposed. • Si@SiC@C nanocomposites reveal good electrochemical performance in LIBs.

  10. Growth of strained Si/relaxed SiGe heterostructures on Si(110) substrates using solid-source molecular beam epitaxy

    Science.gov (United States)

    Arimoto, Keisuke; Nakazawa, Hiroki; Mitsui, Shohei; Utsuyama, Naoto; Yamanaka, Junji; Hara, Kosuke O.; Usami, Noritaka; Nakagawa, Kiyokazu

    2017-11-01

    A strained Si/relaxed SiGe heterostructure grown on Si(110) substrate is attractive as a platform for high-hole-mobility Si-based electronic devices. To improve the electrical property, a smoother surface is desirable. In this study, we investigated surface morphology and microstructural aspects of strained Si/relaxed SiGe/Si(110) heterostructures grown by solid-source (SS) molecular beam epitaxy (MBE). It was revealed that SSMBE provides a way to grow strained Si/relaxed SiGe heterostructures with smooth surfaces. In addition, it was found that the strain in the SiGe layer of the SSMBE-grown sample is highly anisotropic whereas that of the GSMBE-grown sample is almost biaxially relaxed. Along with the surface morphology, the symmetry in degree of strain relaxation has implications for the electrical property. Results of a calculation shows that anisotropic strain is preferable for device application since it confines holes solely in the strained Si layer where hole mobility is enhanced.

  11. Atomistic Modelling of Si Nanoparticles Synthesis

    Directory of Open Access Journals (Sweden)

    Giovanni Barcaro

    2017-02-01

    Full Text Available Silicon remains the most important material for electronic technology. Presently, some efforts are focused on the use of Si nanoparticles—not only for saving material, but also for improving the efficiency of optical and electronic devices, for instance, in the case of solar cells coated with a film of Si nanoparticles. The synthesis by a bottom-up approach based on condensation from low temperature plasma is a promising technique for the massive production of such nanoparticles, but the knowledge of the basic processes occurring at the atomistic level is still very limited. In this perspective, numerical simulations can provide fundamental information of the nucleation and growth mechanisms ruling the bottom-up formation of Si nanoclusters. We propose to model the low temperature plasma by classical molecular dynamics by using the reactive force field (ReaxFF proposed by van Duin, which can properly describe bond forming and breaking. In our approach, first-principles quantum calculations are used on a set of small Si clusters in order to collect all the necessary energetic and structural information to optimize the parameters of the reactive force-field for the present application. We describe in detail the procedure used for the determination of the force field and the following molecular dynamics simulations of model systems of Si gas at temperatures in the range 2000–3000 K. The results of the dynamics provide valuable information on nucleation rate, nanoparticle size distribution, and growth rate that are the basic quantities for developing a following mesoscale model.

  12. Interpretazioni geofisiche della prima serie di triangolazioni eseguite presso la diga di Pieve di Cadore

    Directory of Open Access Journals (Sweden)

    M. C. Spadera

    1958-06-01

    Full Text Available Fra le deformazioni che si possono verificarein un corpo solido elastico, vi è quellache si manifesta sotto forma di variazionedi volume e che è nota con il nome di dilatazione.Ci limiteremo ad una esposizionesommaria.

  13. Reduction in interface defect density in p-BaSi2/n-Si heterojunction solar cells by a modified pretreatment of the Si substrate

    Science.gov (United States)

    Yamashita, Yudai; Yachi, Suguru; Takabe, Ryota; Sato, Takuma; Emha Bayu, Miftahullatif; Toko, Kaoru; Suemasu, Takashi

    2018-02-01

    We have investigated defects that occurred at the interface of p-BaSi2/n-Si heterojunction solar cells that were fabricated by molecular beam epitaxy. X-ray diffraction measurements indicated that BaSi2 (a-axis-oriented) was subjected to in-plane compressive strain, which relaxed when the thickness of the p-BaSi2 layer exceeded 50 nm. Additionally, transmission electron microscopy revealed defects in the Si layer near steps that were present on the Si(111) substrate. Deep level transient spectroscopy revealed two different electron traps in the n-Si layer that were located at 0.33 eV (E1) and 0.19 eV (E2) below the conduction band edge. The densities of E1 and E2 levels in the region close to the heterointerface were approximately 1014 cm‑3. The density of these electron traps decreased below the limits of detection following Si pretreatment to remove the oxide layers from the n-Si substrate, which involved heating the substrate to 800 °C for 30 min under ultrahigh vacuum while depositing a layer of Si (1 nm). The remaining traps in the n-Si layer were hole traps located at 0.65 eV (H1) and 0.38 eV (H2) above the valence band edge. Their densities were as low as 1010 cm‑3. Following pretreatment, the current versus voltage characteristics of the p-BaSi2/n-Si solar cells under AM1.5 illumination were reproducible with conversion efficiencies beyond 5% when using a p-BaSi2 layer thickness of 100 nm. The origin of the H2 level is discussed.

  14. Vertical charge-carrier transport in Si nanocrystal/SiO2 multilayer structures.

    Science.gov (United States)

    Osinniy, V; Lysgaard, S; Kolkovsky, Vl; Pankratov, V; Nylandsted Larsen, A

    2009-05-13

    Charge-carrier transport in multilayer structures of Si nanocrystals (NCs) embedded in a SiO(2) matrix grown by magnetron sputtering has been investigated. The presence of two types of Si NCs with different diameters after post-growth annealing is concluded from transmission-electron microscopy and photoluminescence measurements. Based on the electric field and temperature dependences of capacitance and resistivity, it is established that the carrier transport is best described by a combination of phonon-assisted and direct tunneling mechanisms. Poole-Frenkel tunneling seems to be a less suitable mechanism to explain the vertical carrier transport due to the very high values of refractive indices obtained within this model. The possibility to more effectively collect charge carriers generated by light in structures having Si NCs of different size is discussed.

  15. High-temperature tensile strength of near-stoichiometric SiC/SiC composites

    Science.gov (United States)

    Hironaka, K.; Nozawa, T.; Hinoki, T.; Igawa, N.; Katoh, Y.; Snead, L. L.; Kohyama, A.

    2002-12-01

    In an attempt to characterize mechanical properties of near-stoichiometric SiC/SiC composites, tensile tests were conducted at room temperature in air and at elevated temperature under mild oxidizing gases atmosphere. SiC/SiC composites were fabricated by forced-flow chemical vapor infiltration method using two-dimensional fabrics of carbon coated near-stoichiometric Tyranno™SA fibers. Tensile tests were conducted on composites with two types of lay-up schemes using edge-loading small specimens. The effect of lay-up orientation on the mechanical properties and fracture behavior of composites were also examined. Tensile strength of composite was slightly decreased at 1573 K, while it retained approximately 80% of the strength at room temperature. Porosity dependence on elastic modulus was clearly exhibited.

  16. Nitrogen Plasma Processing of SiO2/4H-SiC Interfaces

    Science.gov (United States)

    Modic, A.; Sharma, Y. K.; Xu, Y.; Liu, G.; Ahyi, A. C.; Williams, J. R.; Feldman, L. C.; Dhar, S.

    2014-04-01

    A nitrogen plasma annealing process for gate dielectric applications in 4H-SiC metal oxide semiconductor (MOS) technology has been investigated. This process results in substantially greater interfacial N coverage at the SiO2/4H-SiC interface and lower interface trap densities than the state-of-the-art nitric oxide (NO) annealing process. Despite these exciting results, the field-effect mobility of MOS field-effect transistors (MOSFETs) fabricated by use of this process is very similar to that of NO-annealed MOSFETs. These results emphasize the importance of understanding mobility-limiting mechanisms in addition to charge trapping in next-generation 4H-SiC MOSFETs.

  17. Simulation and performance comparison of Si and SiC-based interleaved boost converter

    Science.gov (United States)

    Almalaq, Yasser; Alateeq, Ayoob; Matin, Mohammad

    2017-08-01

    In this paper, simulation and performance comparison of Si and SiC based interleaved boost converter is presented. Wide bandgap devices such as silicon carbide and gallium nitride are desirable and recommended in high-power applications because of their capability of operating under high temperature, high switching frequency, and high voltage with reduced switching losses. The main advantage of using SiC materials is the ability to raise the switching frequency which will reduce the size. However, their cost is high compared to Si. In this paper, 60V input voltage is used to get 120V output voltage under 100 KHz switching frequency and 0.5 duty cycle. With the help of LTSpice software, an efficiency comparison between silicon and silicon carbide by considering interleaved boost converter are simulated and studied.

  18. 75-GHz SiGe Heterojunction Bipolor Transistors: GaAs Performance in Si Technology?

    Science.gov (United States)

    1992-05-22

    frequency results of the base-collector junction without penalty on cur- SiGe and Si epitaxial base transistors (cf. Figs. I and rent density...0.60x.3 0.604.3 20 / IT (GHz) 2, 2o . .. 50A SI BJT R(W/Ob) 3.8 s 10 k (0) 60 so’ ’ . . Re (a) is 1985 1990 R (0I) 18 8 Publication Date 0VCE0 M 2.4 3.2...ee ls "SIMS profile for the SiGe-base transistors of 0Fig. 1, The Ge grading is positioned precisely 20 in the most heavily doped region of the base NC

  19. How do students from Student Incubators (SI) use networks and how can SI support the activity?

    DEFF Research Database (Denmark)

    Andersen, Henrik Mariendal

    2015-01-01

    This paper examines Student Entrepreneur’s (SE) use of networks as part of their activities in a Student Incubator (SI). Recommendations are made as to how SI can create activities to support students' use of internal and external relationships and discusses the paradox between running a learning...... is on SEs because students are likely to have a smaller (in size), less well-founded and limited professional network. In addition, an SI is assumed to be characterized by “limitations” related to their student status. So far none has paid any attention to how SEs "compensate for" and/or develop relevant...... internal and external relationships and how SI supports an appropriate project and business development process with these assumptions and “limitations” in mind. To investigate this, a series of qualitative interviews with SEs are conducted, with an emphasis on the use of relationships...

  20. IBA study of SiGe/SiO{sub 2} nanostructured multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Barradas, Nuno P., E-mail: nunoni@ctn.ist.utl.pt [Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 (ao km 139,7), 2695-066 Bobadela LRS (Portugal); Laboratório de Engenharia Nuclear, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 (ao km 139,7), 2695-066 Bobadela LRS (Portugal); Alves, E. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Vieira, E.M.F. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); Parisini, A. [CNR-IMM Sezione di Bologna, via P. Gobetti 101, 40129 Bologna (Italy); Conde, O. [Physics Department and ICEMS, University of Lisbon, 1749-016 Lisboa (Portugal); Martín-Sánchez, J. [Laser Processing Group, Instituto de Óptica, CSIC, C/Serrano 121, 28006 Madrid (Spain); Rolo, A.G. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); Chahboun, A. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); FST Tanger, Physics Department, BP 416 Tanger (Morocco); Gomes, M.J.M. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal)

    2014-07-15

    SiGe/SiO{sub 2} multilayers with layer thickness of 5 nm were deposited with RF magnetron sputtering. The as deposited samples had well defined SiGe amorphous layers. Different annealing treatments were made to promote the formation of SiGe nanocrystals. We report an ion beam analysis study with the Rutherford backscattering and elastic recoil analysis detection techniques, in order to determine the thickness and composition of the nanolayers, and gain insight into the evolution of the roughness of the layers. The results are correlated with other structural properties of the samples, as measured with complementary techniques such as grazing incidence X-ray diffraction annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy.

  1. Specific features of current flow in α-Si : H/Si heterojunction solar cells

    Science.gov (United States)

    Sachenko, A. V.; Kostylyov, V. P.; Sokolovskyi, I. O.; Bobyl', A. V.; Verbitskii, V. N.; Terukov, E. I.; Shvarts, M. Z.

    2017-02-01

    Specific features of the formation of dark I-V characteristics of α-Si: H/Si heterojunction solar cells are investigated taking account the ratio between silicon doping level N d and excess concentration Δ n of electron-hole pairs. It is demonstrated that, at Δ n ≥ Nd, the I-V characteristic is fundamentally different from the characteristic of a classical Shockley diode due the effect of the backside surface (additional drop of the applied voltage). The results of analysis are used to describe the experimental I-V characteristics reported in studies on α-Si: H/Si heterojunction solar cells. Numerical values of the ideality factors of the dark I-V characteristics are obtained by comparing the experimental and calculated curves.

  2. Magnetohydrodynamic (MHD) considerations for liquid metal blanket and a SiC/SiC composite structure

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, R.; Greeff, J. de; Vinche, C. [Commission Europeenne Community, JRC, Vatican City State, Holy See (Italy)

    1998-07-01

    The electrical conductivity was measured on SiC/SiC composite specimens, in the as-received conditions and after neutron irradiation, for temperatures between 20 deg. C and 1000 deg. C. The tests were aimed at estimating the magnitude of MHD effects in liquid metal blankets and a SiC/SiC composites structure. The electrical conductivity of the unirradiated samples increased continuously with temperature and ranged from 330 ({omega} m){sup -1} at 20 deg. C to 550 ({omega} m){sup -1} at 1000 deg.C. The irradiation reduced only slightly the magnitude of {sigma} indicating the materials tested cannot be treated as an electrical insulator in a MHD analysis for liquid metal blankets. (authors)

  3. Positive magnetoresistance in Co40Fe40B20/SiO2/Si heterostructure

    KAUST Repository

    Zhang, Y.

    2016-07-20

    Current-perpendicular-to-plane electronic transport properties and magnetoresistance of amorphous Co40Fe40B20/SiO2/Si heterostructures are investigated systematically. A backward diode-like rectifying behavior was observed due to the formation of a Schottky barrier between Co40Fe40B20 and Si. The junction resistance shows a metal-insulator transition with decreasing temperature in both the forward and reverse ranges. A large positive magnetoresistance (MR) of ∼2300% appears at 200 K. The positive MR can be attributed to the magnetic-field-controlled impact ionization process of carriers. MR shows a temperature-peak-type character under a constant bias current, which is related to the spin-dependent barrier in the Si near the interface. © CopyrightEPLA, 2016.

  4. Betavoltaic device in por-SiC/Si C-Nuclear Energy Converter

    Science.gov (United States)

    Akimchenko, Alina; Chepurnov, Victor; Dolgopolov, Mikhail; Gurskaya, Albina; Kuznetsov, Oleg; Mashnin, Alikhan; Radenko, Vitaliy; Radenko, Alexander; Surnin, Oleg; Zanin, George

    2017-10-01

    The miniature and low-power devices with long service life in hard operating conditions like the Carbon-14 beta-decay energy converters indeed as eternal resource for integrated MEMS and NEMS are considered. Authors discuss how to create the power supply for MEMS/NEMS devices, based on porous SiC/Si structure, which are tested to be used as the beta-decay energy converters of radioactive C-14 into electrical energy. This is based on the silicon carbide obtaining by self-organizing mono 3C-SiC endotaxy on the Si substrate. The new idea is the C-14 atoms including in molecules in the silicon carbide porous structure by this technology, which will increase the efficiency of the converter due to the greater intensity of electron-hole pairs generation rate in the space charge region. The synthesis of C-14 can be also performed by using the electronically controlled magneto-optic chamber.

  5. High-temperature tensile strength of near-stoichiometric SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Hironaka, K. E-mail: keisuke@iae.kyoto-u.ac.jp; Nozawa, T.; Hinoki, T.; Igawa, N.; Katoh, Y.; Snead, L.L.; Kohyama, A

    2002-12-01

    In an attempt to characterize mechanical properties of near-stoichiometric SiC/SiC composites, tensile tests were conducted at room temperature in air and at elevated temperature under mild oxidizing gases atmosphere. SiC/SiC composites were fabricated by forced-flow chemical vapor infiltration method using two-dimensional fabrics of carbon coated near-stoichiometric Tyranno SA fibers. Tensile tests were conducted on composites with two types of lay-up schemes using edge-loading small specimens. The effect of lay-up orientation on the mechanical properties and fracture behavior of composites were also examined. Tensile strength of composite was slightly decreased at 1573 K, while it retained approximately 80% of the strength at room temperature. Porosity dependence on elastic modulus was clearly exhibited.

  6. Physical studies of strained Si/SiGe heterostructures. From virtual substrates to nanodevices

    Energy Technology Data Exchange (ETDEWEB)

    Minamisawa, Renato Amaral

    2011-10-21

    During the past two decades, the decrease in intrinsic delay of MOSFETs has been driven by the scaling of the device dimensions. The performance improvement has relied mostly in the increase of source velocity with gate scaling, while the transport properties of the channel have remained constant, i.e., those of conventional Si. Starting at the 90 nm node, uniaxial strain has been introduced in the transistor channel in order to further increase the source velocity. Beyond the 32 nm node, novel channel materials, with superior carrier velocities, and novel device architectures are required in order to continue the performance enhancement of MOSFETs while preserving the electrostatic control. In this Thesis, different physical aspects of strained Si and SiGe materials are investigated as a mean to increase carrier velocity in MOSFET channels. Novel approaches for the fabrication of strained Si based on ion implantation and anneal induced relaxation of virtual substrates are developed. The strain relaxation of SiGe layers is improved using a buried thin Si:C layer in the Si(100) substrate. Further, a Si{sup +} ion implantation and annealing method is investigated for relaxing virtual substrates using lower implantation dose. Finally, the uniaxial relaxation of {l_brace}110{r_brace} surface oriented substrates is demonstrated using a He ion implantation and anneal technique. Apart of channel material studies, the fundamental and technological challenges involved in the integration of strained Si and SiGe into MOSFETs are assessed. The impact of source and drain formation on the elastic strain and electrical properties of strained Si layers and nanowires is examined. Also, the formation of ultra-shallow junction in strained Si/strained Si{sub 0.5}Ge{sub 0.5}/SSOI heterostructures is investigated using different types of ion implanted specie and annealing. The results show that BF{sup +}{sub 2} implantation and low temperature annealing are suitable approaches for

  7. Blue photoluminescence and local structure of Si nanostructures embedded in SiO2 matrices

    Science.gov (United States)

    Zhang, Qi; Bayliss, S. C.; Hutt, D. A.

    1995-04-01

    Strong and stable blue photoluminescence (PL), visible to the naked eye under 0.4 μW of 300 nm and 2.7 μW of 370 nm excitation, has been observed for samples of Si clusters embedded in SiO2 matrices, prepared by rf co-sputtering followed by N2 annealing at 800 °C. Si K-edge extended x-ray absorption fine structure (EXAFS) and near-edge x-ray absorption fine structure (NEXAFS) strongly suggest the existence of Si nanoclusters with crystalline cores in the efficient emitting material. The PL excitation dependence is explained by an increase in the conduction band density of states deep in the band, and the formation of a band tail.

  8. Si-H induced synthesis of Si/Cu2O nanowire arrays for photoelectrochemical water splitting

    Science.gov (United States)

    Zhang, Shaoyang; She, Guangwei; Li, Shengyang; Mu, Lixuan; Shi, Wensheng

    2018-01-01

    We report a facile and low-cost method to synthesize Si/Cu2O heterojunction nanowire arrays, without SiOx, at the Si/Cu2O interface. The reductive Si–H bonds on the surface of Si nanowires plays a key role in situ by reducing Cu(II) ions to Cu2O nanocubes and avoiding the SiOx interface layer. Different pH values would vary the electrochemical potential of reactions and as a result, different products would be formed. Utilized as a photoanode for water splitting, Si/Cu2O nanowire arrays exhibit good photoelectrochemical performance.

  9. Di Dio che viene dall'Ikea

    Directory of Open Access Journals (Sweden)

    Paolo Amodio

    2014-06-01

    Full Text Available The possibilities offered by the last generation of scanning and transmission electron microscopes allow to spy on the inner structure of biological tissues and to observe bio-architectures which multiply – overcoming classical categories – the conventional standards of order and symmetry, revealing hierarchically organized micro- and nano-structures. These new paradigms form the basis for creating effective physical-mathematical models, leading to simulate (and predict the destiny of biological organisms and elementary “living” systems. The whole world of Research is therefore forced to an updated (bien sûr, more authentic (maybe, necessary (?, interdisciplinary (was ist das? common thinking over? What’s the buzz about Beauty?

  10. La nuova fisica che ci aspetta

    CERN Multimedia

    Shiga, David

    2007-01-01

    The big accelerator that will enter in function at CERN at the end of the year will have the hard task to verify the relevance of the string theory, today the better candiddate to be the famous "theory of everything" that physicists are looking for since decades. (1 page)

  11. Che cosa impariamo dalla crisi argentina

    OpenAIRE

    Bianchi Patrizio

    2002-01-01

    This article explores the industrial roots of the present Argentina's crisis. Since the mid of 19th century, Argentina developed a model of social modernization without industrialization, based on export of primary commodity to Western developed countries. This model was exhausted during the 1930s; crisis, because of the ring of protectionism in the Western countries and replaced by an import-substitution approach, which promoted a wide range of small sub-optimal plants. In the mid-1970s, the...

  12. Initiation Mechanisms in IHE and CHE Materials

    Science.gov (United States)

    Jardine, Andrew; Williamson, David; Walley, Stephen; Palmer, Stewart; Leppard, Claire; Fracture and Shock Physics Group, University of Cambridge Team; AWE Team

    2013-06-01

    Impact sensitivity and subsequent impact initiation is one of the key characteristics of explosive materials. Various standardised tests exist, such as the Rotter or BAM impact tests, which allow the relative sensitivity of different materials to be characterised. However, these provide little insight into the underlying behaviour of the material. The use of a periscopic glass-anvil drop-weight apparatus has proven to provide valuable information about the hotspot initiation of many materials. In this paper we describe experiments which apply the technique, in conjunction with high speed video and additional diagnostic instrumentation, to study the mechanism of initiation of modern explosive materials including TATB, LLM-105, Fox-7, HMX, RDX and PETN.

  13. Che cos'e la storia?

    OpenAIRE

    Vella, Andrew P.

    1984-01-01

    In this article, the author tackles some important points when it comes to teaching history at University level; 1. A definition of History 2. The difficulties in writing History 3. Historical objectives and 4. Research techniques and Historical sources.

  14. Origin of multistate resistive switching in Ti/manganite/Si$O_x$/Si heterostructures

    OpenAIRE

    Acevedo, W. Román; Acha, C.; Sánchez, M. J.; Levy, P.; Rubi, D.

    2016-01-01

    We report on the growth and characterization of Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/Si$O_x$/n-Si memristive devices. We demonstrate that using current as electrical stimulus unveils an intermediate resistance state, in addition to the usual high and low resistance states that are observed in standard voltage controlled experiments. Based on thorough electrical characterization (impedance spectroscopy, current-voltage curves analysis), we disclose the contribution of three different microscopic reg...

  15. Vaporization of SiO2 and MgSiO3

    Science.gov (United States)

    Stixrude, L. P.; Xiao, B.

    2016-12-01

    Vaporization of SiO2 and MgSiO3B Xiaoa and L Stixrude*a, a Department of Earth Sciences, University College London, WC1E 6BT London, UK *presenting author, email: l.stixrude@ucl.ac.uk Vaporization is an important process in Earth's earliest evolution during which giant impacts are thought to have produced a transient silicate atmosphere. As experimental data are very limited, little is known of the near-critical vaporization of Earth's major oxide components: MgO and SiO2. We have performed novel ab initio molecular dynamics simulations of vapor-liquid coexistence in the SiO2 and MgSiO3 systems. The simulations, based on density functional theory using the VASP code, begin with a suitably prepared liquid slab embedded in a vacuum. During the dynamical trajectory in the canonical ensemble, we see spontaneous vaporization, leading eventually to a steady-state chemical equilibrium between the two coexisting phases. We locate the liquid-vapor critical point at 6600 K and 0.40 g/cm3 for MgSiO3 and 5300 K and 0.43 g/cm3 for SiO2. By carefully examining the trajectories, we determine the composition and speciation of the vapor. For MgSiO3, We find that the vapor is significantly richer in Mg, O, and atomic (non-molecular) species than extrapolation of low-temperature experimental data has suggested. These results will have important implications for our understanding of the initial chemistry of the Earth and Moon and the initial thermal state of Earth.

  16. Marbled texture of sputtered Al/Si alloy thin film on Si

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, M.G. [Physics Department and NIS Interdepartmental Center, University of Torino, via P. Giuria 1, 10125 Torino (Italy); Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Muñoz-Tabares, J.A.; Chiodoni, A. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy); Sgorlon, C. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Para, I. [Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Carta, R.; Richieri, G. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Bejtka, K. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy); Merlin, L. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Vittone, E. [Physics Department and NIS Interdepartmental Center, University of Torino, via P. Giuria 1, 10125 Torino (Italy)

    2016-08-01

    DC magnetron sputtering is a commonly used technique for the fabrication of silicon based electronic devices, since it provides high deposition rates and uniform large area metallization. However, in addition to the thickness uniformity, coating optical uniformity is a crucial need for semiconductor industrial processes, due to the wide use of optical recognition tools. In the silicon-based technology, aluminum is one of the most used materials for the metal contact. Both the pre-deposition substrate cleaning and the sputtering conditions determine the quality and the crystalline properties of the final Al deposited film. In this paper is shown that not all the mentioned conditions lead to good quality and uniform Al films. In particular, it is shown that under certain standard process conditions, Al/Si alloy (1% Si) metallization on a [100] Si presents a non-uniform reflectivity, with a marbled texture caused by flakes with milky appearance. This optical inhomogeneity is found to be caused by the coexistence of randomly orient Al/Si crystal, with heteroepitaxial Al/Si crystals, both grown on Si substrate. Based on the microstructural analysis, some strategies to mitigate or suppress this marbled texture of the Al thin film are proposed and discussed. - Highlights: • Sputtered Al/Si layers deposited on Si present evident optical non-uniformity • It could be an issue for optical recognition tools used in semiconductor industries • Optical non-uniformity is due to randomly oriented growth of Al grains. • Substrate misorientation and process temperature can mitigate the problem.

  17. Nanoscale Structuring by Misfit Dislocations in Si1-xGex/Si Epitaxial Systems

    DEFF Research Database (Denmark)

    Shiryaev, S.Y.; Jensen, Flemming; Hansen, J. Lundsgaard

    1997-01-01

    New capabilities of misfit dislocations for spatial manipulation of islands in Si1-xGex/Si heteroepitaxial systems have been elucidated. Formation of highly ordered Ge-island patterns on substrates prestructured by slip bands of misfit dislocations is revealed. The major sources leading...... to the ordering are identified to be dislocation strain fields at the surface and modifications of the nearsurface-layer morphology induced by dislocation slip....

  18. Influence of Oxidation Parameters on Roughness at the Si-SiO2 Interface.

    Science.gov (United States)

    1980-01-01

    between Si and SiO 2 down to the resolution of 1 nm (corresponding to about 3 atomic layers). Krivanek and coworkers ( 21 ) demonstrated even with a...Buiocchi, M.S. Abrahams, W.E. Ham, Appl. Phys. Lett. 30 (1977) 120 21. O.L. Krivanek , T.T. Sheng and D.C. Tsui, Appl. Phys. Lett. 32 (1978) 437 22. H.H

  19. Modeling Environmental Degradation of SiC/BN/SiC CMCs (Preprint)

    Science.gov (United States)

    2017-04-28

    AFRL-RX-WP-JA-2017-0308 MODELING ENVIRONMENTAL DEGRADATION OF SIC/BN/SIC CMCS (PREPRINT) Craig Przybyla and Michael K Cinibulk...2017 Interim 22 July 2013 – 6 January 2017 4. TITLE AND SUBTITLE MODELING ENVIRONMENTAL DEGRADATION OF SIC/BN/SIC CMCS (PREPRINT) 5a. CONTRACT...91360 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39-18 Modeling environmental degradation of SiC/BN/SiC CMCs Triplicane A

  20. FOCUS SULLA SENSIBILITÀ LINGUISTICA: LA TRADUZIONE COLLABORATIVA NELLA CLASSE DI LINGUA

    Directory of Open Access Journals (Sweden)

    Gioia Panzarella

    2017-03-01

    Full Text Available Può la traduzione facilitare la didattica delle lingue moderne? Questo articolo illustra i primi risultati di un progetto di ricerca in corso presso l’Università di Warwick, Regno Unito, (in collaborazione con l’Università di Monash, Australia che riguarda l’uso della traduzione collaborativa nell’insegnamento delle lingue a studenti universitari e a studenti Erasmus. Le autrici si sono concentrate sui vantaggi in termini di sensibilità linguistica e consapevolezza culturale derivanti da un particolare modello di traduzione collaborativa. Quando la proposta di “Collaborative Translation: A Model for Inclusion” si applica al particolare contesto della didattica delle lingue, infatti, l’insegnante e gli studenti esplorano insieme il processo di traduzione di un testo verso la lingua madre degli studenti. Il valore di questo approccio risiede nel privilegiare una messa in discussione della corrispondenza univoca tra due termini in due diverse lingue: l’insegnante è infatti un collaboratore della traduzione che agisce come facilitatore, chiedendo agli studenti-collaboratori di assumersi la responsabilità della traduzione. L’abilità linguistica in sé, di conseguenza, ha un ruolo secondario rispetto alla curiosità e alla riflessione linguistica nei confronti della propria lingua. I  workshop di inglese e di italiano sono stati rivolti rispettivamente a studenti principianti e a studenti avanzati. Focus on language sensitivity: collaborative translation in language class How can translation facilitate language learning? Reporting on the preliminary findings of an ongoing research project into the use of translation in language learning at the University of Warwick, UK (in collaboration with the University of Monash, Australia, the authors investigate the advantages of a specific translation model in terms of linguistic sensitivity and cultural awareness. The ‘Collaborative Translation: A Model for Inclusion’ prototype is