Search results for "SHIFT"
showing 10 items of 1226 documents
Actively Q-switched DFB fiber laser for Brillouin sensor applications
2009
Q-switching of distributed feedback (DFB) fiber lasers permits to achieve high peak powers, preserving an ultra narrow linewidth [1,2]. The development of a new in-line acousto-optic modulator based on a magnetostrictive actuator, instead of a piezoelectric-based device, permits an efficient excitation of elastic pulses propagating along the optical fiber and an easy access to both emission outputs of the laser. The repetition rate can be continuously adjusted, as well as the amplitude of the elastic pulses. The interaction of these elastic pulses with a fiber Bragg grating written in an erbium-doped fiber permits an actively Q-switched operation of the DFB fiber laser [3]. The birefringenc…
Single- to three-wavelength switchable ytterbium-doped fiber laser based on intracavity induced loss by a long-period holey fiber grating
2011
In this paper, we propose and demonstrate a versatile and simple single-, dual- and three-wavelength switchable ytterbium-doped fiber laser using the intracavity induced-loss generated by a mechanically induced long-period grating (MLPFG) in a holey fiber. The laser net gain in the cavity is reshaped through the MLPFG by adjusting the twist rate and the pressure of the holey fiber in the long-period grating. In this way, the twist response of the MLPFG enables the laser to switch between the single-, dual-, and three-wavelength operations and the tuning of the simultaneous two- and three-wavelengths. These results are of great interest in the design of flexible multiwavelength sources with …
Language Mediation and Aspects of Accommodation in the Use of ELF
2014
There are numerous varieties of English spoken in Italy today, each repre-sented by one or more of the various migrant communities living in the country. These manifestations of World englishes reflect a wide range of lexical, syntactical, phonetic, pragmatic, interpersonal and cultural features. This paper argues that an interpreter or language mediator trained in standard English may not necessarily be able to comprehend or make him/herself understood adequately in other varieties of English. Thus, the recruitment of mediators/interpreters requires a certain amount of caution in terms of language choice. In order to investigate intelligibility, comprehensibility and accommodation in the c…
Poor nutritional quality of primary producers and zooplankton driven by eutrophication is mitigated at upper trophic levels
2022
Eutrophication and rising water temperature in freshwaters may increase the total production of a lake while simultaneously reducing the nutritional quality of food web components. We evaluated how cyanobacteria blooms, driven by agricultural eutrophication (in eutrophic Lake Köyliöjärvi) or global warming (in mesotrophic Lake Pyhäjärvi), influence the biomass and structure of phytoplankton, zooplankton, and fish communities. In terms of the nutritional value of food web components, we evaluated changes in the ω-3 and ω-6 polyunsaturated fatty acids (PUFA) of phytoplankton and consumers at different trophic levels. Meanwhile, the lakes did not differ in their biomasses of phytoplankton, zoo…
Regional Powers as Leaders or Rambos? The Ambivalent Behaviour of Brazil and South Africa in Regional Economic Integration
2013
The behaviour of regional powers towards their own regions is often volatile in the developing world, which leads to unstable integration processes. This article argues that this volatility is due to limited intra-regional gains from regional integration in developing regions, which implies that the behaviour of regional powers is constrained by extra-regional economic interests. When regional integration is not in conflict with extra-regional interests, regional powers provide regional leadership. However, when extra-regional interests are in conflict with regional integration, regional powers become regional Rambos. This argument is illustrated with the two examples of Brazil's behaviour …
El sector no lucrativo en el marco de la nueva era tecnológica: el desafío del Crowdfunding social en España. Análisis del caso de la asociación Alba…
2017
Los albores del siglo XXI se presentan a las economías y las sociedades en el marco de un desafiante doble cambio de paradigma. Uno, alentado por el neoliberalismo gobernante en gran parte del mundo avanzado, que ha provocado que la propia sociedad admita la arresponsabilidad de las estructuras gobernantes en la prestación de los servicios que componen el Estado del bienestar. Otro, tecnológico, que ha cambiado el modo en que la sociedad se informa, se comunica y se relaciona. Frente a estas dos realidades la sociedad civil ha tomado conciencia de su papel transformador e impulsor de cambios, así como de las crecientes necesidades de atención social que han surgido en este principio de sigl…
Reciprocal regulation of the human sterol regulatory element binding protein (SREBP)-1a promoter by Sp1 and EGR-1 transcription factors.
2007
AbstractSterol regulatory element binding protein (SREBP)-1a is a transcription factor that is highly expressed in actively growing cells, and is involved in the biosynthesis of cholesterol, fatty acids and phospholipids. We have mapped the minimal human SREBP-1a promoter region to 75bp upstream of the translation start site where we discovered a functional role for the 3 GC-boxes containing overlapping sites for the Sp1 and EGR-1 transcription factors. Intact SP1-binding sites are essential for promoter activity, whereas EGR-1 suppresses the transcription of the human SREBP-1a promoter. These results reveal a novel physiologically relevant transcriptional mechanism for the reciprocal regul…
Initial state radiation experiment at MAMI
2014
In an attempt to contribute further insight into the discrepancy between the Lamb shift and elastic scattering determinations of the proton charge radius, a new experiment at MAMI is underway, aimed at measuring proton form-factors at very low momentum transfers by using a new technique based on initial state radiation. This paper reports on the conclusions of the pilot measurement performed in 2010, whose main goal was to check the feasibility of the proposed experiment and to recognize and overcome any obstacles before running the full experiment. The modifications to the experimental apparatus are then explained which significantly improved the quality of data collected in the full scale…
Exactly solvable model of two three-dimensional harmonic oscillators interacting with the quantum electromagnetic field: The far-zone Casimir-Polder …
2005
We consider two three-dimensional isotropic harmonic oscillators interacting with the quantum electromagnetic field in the Coulomb gauge and within dipole approximation. Using a Bogoliubov-like transformation, we can obtain transformed operators such that the Hamiltonian of the system, when expressed in terms of these operators, assumes a diagonal form. We are also able to obtain an expression for the energy shift of the ground state, which is valid at all orders in the coupling constant. From this energy shift the nonperturbative Casimir-Polder potential energy between the two oscillators can be obtained. When approximated to the fourth order in the electric charge, the well-known expressi…
Energy level shifts of a uniformly accelerated atom in the presence of boundary conditions
2009
We discuss the radiative level shifts of an atom moving with uniform acceleration near an infinite reflecting plate. We first consider the case of a two-level system interacting with a massless scalar field in the vacuum state. The acceleration of the two-level atom is supposed in a direction parallel to the conducting plate. We evaluate the contribution of vacuum fluctuations and of the radiation reaction field to the energy shift of the atomic levels, and discuss their behaviour as a function of the atomic acceleration and of the atom-plate distance. Then, we investigate the more general case of an hydrogen atom accelerating near a perfectly reflecting plate and interacting with the elect…