Search results for "Lector"
showing 10 items of 341 documents
Detection system for forward emitted photons at the Experimental Storage Ring at GSI
2013
A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the b…
A new method to measure the wavelength of single-mode pulsed lasers with a scanning Michelson interferometer
1994
We report on the possibility to measure the wave-lengths of pulsed single-mode lasers by means of a two-beam Michelson interferometer in motion [1,2]. The corner reflector moves with a nearly constant speed creating a path differenceL so thatL/C ≪ 1/Δν, Δν being the spectral width of the laser to be measured. The reference laser is a stabilized He-Ne (Spectra-Physics, model 117 A) to a precision of the order of two parts in 109. The fringe pattern of the two beams (reference beam and measured beam) is sampled simultaneously with a repetition rate of 40 ms. With this new method, the frequency doubled injection-seeded Nd: YAG laser wavelength has been measured with an accuracy of the order of…
Light weight, thin plastic foil, X-ray telescopes
2002
We present results from a program to develop an X-ray telescope made from thin plastic shells. Our initial results have been obtained from multi-shell cylindrical lenses that are used in a point-to-point configuration to image the small focal spot of a an X-ray tube on a microchannel plate detector. We describe the steps that led up to the present design and present data from the tests that have been used to identify the properties of the plastic material that make it a suitable X-ray reflector. We discuss two applications of our technology to X-ray missions that are designed to address some of the scientific priorities set forth in NASA's long term plans for high energy astrophysics. One m…
Noise fiber lasers
2021
In this paper, we present a brief review of the noise operation mode of fiber lasers. These lasers were studied recently by collaborative group that includes researchers, professors, and Ph.D. students from the Centro de Investigaciones en Optica, A.C. (Leon, Guanajuato, Mexico) and from the Universidad de Valencia (Valencia, Spain). Meanwhile, the pioneer works in this topic important for understanding the physics behind fiber lasers’ operation and for practical applications were done with the active participation of Dr. Evgeny Kuzin from the Instituto Nacional de Astrofisica, Optica y Electronica (Puebla, Mexico) and Dr. Georgina Beltrán-Pérez from the Benemérita Universidad Autónoma de P…
Cuando la izquierda quiere ser de centro
2002
Diritti di partecipazione politica e piattaforme digitali, alcune riflessioni
2022
Questo scritto affronta il tema dell’impatto dei social networks sui diritti di partecipazione politica, con riguardo al diritto all’informazione, al diritto di associarsi in partiti, al diritto di voto come esito di campagne elettorali digitali. Il mutamento della comunicazione politica e del dibattito pubblico refluisce sulla correttezza dei processi democratici; ciò pone l’esigenza della regolazione dei social networks quale spazio mediatico utilizzato dai soggetti politici (individui od organizzazioni) per influenzare la formazione dell’opinione pubblica e costruire il consenso a proprio favore, soprattutto nell’ambito delle campagne elettorali. L’articolo si sofferma, dunque, sui probl…
Análisis automatizado de encuadres mediáticos. Estudio de la cobertura en prensa del debate 7d 2015 : el debate decisivo
2017
La digitalización y el almacenamiento de las noticias en bases de datos favorece la investigación de grandes lotes de información textual mediante el análisis de contenido asistido por computadora. Varios autores señalan las ventajas de la utilización de este tipo de programas en los estudios de framing. El objetivo de este trabajo es analizar la presencia en los medios de comunicación de los encuadres utilizados por los participantes en el debate electoral televisado el 7 de diciembre de 2015 con motivo de las elecciones generales españolas de 2015. En el estudio implementamos un análisis automatizado de contenido con el programa WordStat para extraer los encuadres de los textos analizados…
Proces selekcji kandydatów partii politycznych w wyborach Prezydenta RP – motywacje, dylematy, strategie
2022
Wybory prezydenckie pomimo dużego stopnia spersonalizowania, stanowią ważną przestrzeń rywalizacji międzypartyjnej. Doświadczenia polskich elekcji prezydenckich pokazują, że są one zdominowane przez kandydatów partyjnych. Podstawowym celem niniejszego artykułu, jest ukazanie procesu selekcji kandydatów partii politycznych na urząd Prezydenta RP, jako jednego z kontekstów wyborów prezydenckich w Polsce. Istotnym punktem rozważań jest odniesienie wskazanego procesu do aktywności przywódców partyjnych w tym zakresie, a dokładnie zauważalnej tendencji do rezygnacji z kandydowania. Trend ten wiąże się z wykorzystywaniem przez partie polityczne tzw. surogatów, czyli kandydatów zastępczych. Porusz…
The participation paradox: demand for and fear of immigrant participation
2019
In this paper, we address the ambivalence in European immigrant integration discourses toward the political participation of immigrants. We show how this ambivalence manifests in what we call a ‘participation paradox’, which is constituted by two apparently conflicting, but potentially mutually reinforcing characteristics of the discourse. The first emphasizes the need for immigrants to be active in order to attain a well-integrated society and well-functioning democratic polity; the second is a call for the protection of liberal democratic institutions from the alleged ‘illiberal threats’ that migrants pose to society. Immigrant participation is thus both demanded and feared. Using illustr…
Room-temperature polariton luminescence from a bulk GaN microcavity
2006
We report strong exciton-photon coupling at room temperature in a hybrid high quality bulk 3 lambda/2 GaN cavity with a bottom lattice-matched AlInN/AlGaN distributed Bragg reflector through angle-resolved polarized photoluminescence (PL). Coupling of the optically active free excitons (X-A, X-B, and X-C) to the cavity mode is demonstrated, with their contribution to the PL spectra varying with polarization. Under TE polarization, exciton oscillator strengths for X-A and X-B are about one order of magnitude larger than in bulk GaAs. Photoluminescence exhibits a strong bottleneck effect despite its thermal lineshape.