7,642 research outputs found

    The anomaly-induced effective action and natural inflation

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    The anomaly-induced inflation (modified Starobinsky model) is based on the application of the effective quantum field theory approach to the Early Universe. We present a brief general review of the model and show that it does not require a fine-tuning for the parameters of the theory or initial data, gives a real chance to meet a graceful exit to the FRW phase and also has positive features with respect to the metric perturbations.Comment: Invited talk at the International Workshop on Astroparticle and High Energy Physics, October 14 - 18, 2003, Valencia, Spai

    Top-Quark Production and Decay in the MSSM

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    We review the features of top-quark decays and loop-induced effects in the production cross section and CP-violating observables of e+e- -> t t-bar which are specific to the R-parity conserving Minimal Supersymmetric Standard Model (MSSM).Comment: LaTeX, 28 pages, 10 figures included, uses cite.sty. Contribution to the proceedings of the 2nd Joint ECFA/DESY Workshop on Physics and Detectors for a Linear Electron-Positron Collider. References adde

    Efficient generation of an isolated single-cycle attosecond pulse

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    A new method for efficiently generating an isolated single-cycle attosecond pulse is proposed. It is shown that the ultraviolet (UV) attosecond pulse can be utilized as a robust tool to control the dynamics of electron wave packets (EWPs). By adding a UV attosecond pulse to an infrared (IR) few-cycle pulse at a proper time, only one return of the EWP to the parent ion is selected to effectively contribute to the harmonics, then an isolated two-cycle 130-as pulse with a bandwidth of 45 eV is obtained. After complementing the chirp, an isolated single-cycle attosecond pulse with a duration less than 100 as seems achievable. In addition, the contribution of the quantum trajectories can be selected by adjusting the delay between the IR and UV fields. Using this method, the harmonic and attosecond pulse yields are efficiently enhanced in contrast to the scheme [G. Sansone {\it et al.}, Science {\bf314}, 443 (2006)] using a few-cycle IR pulse in combination with the polarization gating technique.Comment: 5 pages, 4 figure

    In vitro and in vivo expression of foreign genes by transmissible gastroenteritis coronavirus-derived minigenomes

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    A helper-dependent expression system based on transmissible gastroenteritis coronavirus (TGEV) has been developed using a minigenome of 3·9 kb (M39). Expression of the reporter gene {beta}-glucuronidase (GUS) (2–8 µg per 106 cells) and the porcine respiratory and reproductive syndrome virus (PRRSV) ORF5 (1–2 µg per 106 cells) has been shown using a TGEV-derived minigenome. GUS expression levels increased about eightfold with the m.o.i. and were maintained for more than eight passages in cell culture. Nevertheless, instability of the GUS and ORF5 subgenomic mRNAs was observed from passages five and four, respectively. About a quarter of the cells in culture expressing the helper virus also produced the reporter gene as determined by studying GUS mRNA production by in situ hybridization or immunodetection to visualize the protein synthesized. Expression of GUS was detected in the lungs, but not in the gut, of swine immunized with the virus vector. Around a quarter of lung cells showing replication of the helper virus were also positive for the reporter gene. Interestingly, strong humoral immune responses to both GUS and PRRSV ORF5 were induced in swine with this virus vector. The large cloning capacity and the tissue specificity of the TGEV-derived minigenomes suggest that these virus vectors are very promising for vaccine development

    Análisis bibliométrico de las publicaciones científicas españolas en la categoría Construction & Building Technology de la base de datos Web of Science (1997-2008)

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    En este trabajo se analizan las publicaciones procedentes de instituciones españolas recogidas en las revistas de la categoría Construction & Building Technology de la base de datos Web of Science para el periodo 1997-2008. El número de revistas incluidas es de 35 y el número de artículos publicados ha sido de 760 (Article o Review). Se ha realizado una evaluación bibliométrica con dos nuevos parámetros: Factor de Impacto Ponderado y Factor de Impacto Relativo; asimismo se incluyen el número de citas y el número de documentos a nivel institucional. Entre los centros con una mayor producción científica destaca, como era de prever, el Instituto de Ciencias de la Construcción Eduardo Torroja (CSIC), mientras que atendiendo al Factor de Impacto Ponderado ocupa el primer lugar la Universidad de Vigo. Por otro lado, sólo dos revistas Cement and Concrete Research y Materiales de Construcción aglutinan el 45.26% de toda la producción científica española, con 172 trabajos cada una de ellas. En cuanto a la colaboración internacional, destacan países como Inglaterra, México, Estados Unidos, Italia, Argentina y Franci

    Ultrafast Laser Inscription of Buried Waveguides in W-TCP Bioactive Eutectic Glasses

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    Since the first report of Davis in 1996, ultrafast laser inscription (ULI) has been widely used to fabricate buried optical devices such as active and passive waveguides inside dielectric materials. In this technique, ultra-short and ultra-intense laser pulses are tightly focused inside transparent materials leading to laser-induced nonlinear processes in the focal volume. The energy density deposited into the submicron focal volume can reach several of MJcm−3 and hence, may trigger dramatic changes in a strongly localized region, whereas the surrounding bulk material remains unchanged. This technique can be used from void formation to weak refractive index modification, which is the key feature to create buried optical waveguides. In this chapter, firstly, we review the fundamentals of the ultrafast laser inscription technique to produce optical waveguides inside dielectric materials such as crystals and glasses. Next, as an example, we revise the application of this technique to create buried waveguides inside bioactive glasses and specifically, inside W-TCP eutectic glasses

    Per a què serveix un sincrotró?

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    La construcció d'un modern sincrotró a Cerdanyola del Vallès costarà molts diners a la hisenda pública. Hem de tenir arguments per a respondre quan els nostres alumnes ens facin preguntes com ara: què és un sincrotró? Per a què serveix? Està justificada, aquesta despesa

    Análisis bibliométrico mundial de BIM a través de la colección principal de la Web of Science (2003-2017)

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    The main objective is to perform a quantitative and qualitative analysis from the institutional point of view of the related research on Building Information Modeling (BIM) collected in the Web of Science Core Collection during the period 2003- 2017. For this, all documents of the type ‘article’ or ‘review’ were reviewed and several bibliometric indicators analyzed. Similarly, the international dissemination of the research of the 16 most productive countries was analyzed, indicating the publication journals of each country and concluding that the main journals. USA is the most productive country although with a relative impact factor slightly higher than average due to the dispersion of its publications in journals of medium or low impact. It also shows how Curtin University (Australia) and the Georgia Institute of Technology (USA) have been the most productive and high impact institutions, although the outstanding rise of Hong Kong Polytechnic University is noted.El principal objetivo es realizar un análisis cuantitativo y cualitativo desde el punto de vista institucional de la investigación relacionada con BIM presente en la colección principal de la Web of Science durante el período 2003-2017. Para ello, fueron revisados los registros del tipo ‘artículo’ o ‘revisión’ y se analizaron diferentes indicadores bibliométricos. La difusión internacional de investigación de los 16 países más productivos fue analizada, indicando las revistas de publicación de cada país, así como las principales revistas. Asimismo, EE.UU. es el país más productivo, aunque con un factor de impacto relativo algo mayor que la media debido a la dispersión de sus publicaciones en revistas de medio y bajo impacto, y la Universidad de Curtin (Australia) y el Instituto de Tecnología de Georgia (EE.UU.) son las instituciones más productivas y con alto impacto, sobresaliendo también la Universidad Politécnica de Hong Kong

    Continuous spectra in high-harmonic generation driven by multicycle laser pulses

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    We present observations of the emission of XUV continua in the 20-37 eV region by high harmonic generation (HHG) with 44-7 fs7\ \mathrm{fs} pulses focused onto a Kr gas jet. The underlying mechanism relies on coherent control of the relative delays and phases between individually generated attosecond pulse, achievable by adjusting the chirp of the driving pulses and the interaction geometry. Under adequate negative chirp and phase matching conditions, the resulting interpulse interference yields a continuum XUV spectrum, which is due to both microscopic and macroscopic (propagation) contributions. This technique opens the route for modifying the phase of individual attosecond pulses and for the coherent synthesis of XUV continua from multicycle driving laser pulses without the need of an isolated attosecond burst.Comment: 14 pages, 5 figures. Submitted to Physical Review
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