Search results for "Signal"
showing 10 items of 6924 documents
Space-Time Analogies in Optics
2011
Abstract The so-called space-time analogy constitutes a source of inspiration to understand, engineer, and implement new systems for ultrafast optical signal processing based on concepts borrowed from the well-established field of Fourier Optics. In this review, we start by describing in a comprehensive manner the most basic notions of this analogy and discuss some recent developments with state-of-the-art technology, including the silicon-chip-based time lens and ultra-dispersive Raman devices, among others. Apart from the applications in optical communications, special emphasis is paid on the collateral benefits that the “ultra” appellative brings in fields as diverse as optical frequency…
Nonlinear theory of slow light.
2011
In the framework of the nonlinear Λ model, propagation of solitons was analysed in atomic vapours and Bose–Einstein condensates. The complicated nonlinear interplay between fast and slow-light solitons in a Λ -type medium was shown to facilitate control of its optical transparency and formation of optical gates. An exact analytical description was given for the deceleration, stopping and revival of slow-light solitons in the experimentally relevant non-adiabatic regime. A stopping slow-light soliton imprints a localized immobile polarization pattern in the medium, which, as explicitly demonstrated here, can be used as a bit of readable optical memory. The whole process can be controlled wi…
Limits for the Generation of Ultra-Wideband Signals with the Incoherent-Pulse-Shaping Technique
2007
Recently, an nil-optical technique to generate arbitrary RF waveforms through Altering of the spectral density function of a broadband spectrally incoherent optical source has been introduced. The spectrum is tailored so that the output averaged intensity after large temporal modulation and subsequent distortion in a group-delay-dispersion circuit becomes the user-defined waveform. In general, there is a tradeoff between the spectral width and the signal-to-noise ratio of the output signal. Here, we provide an analytical treatment of the problem based on the optical coherence theory. In particular, we analyze the possibility to employ this technique for ultra-wideband (UWB) applications.
A Multiwavelength Investigation of the Relationship Between 2CG135+1 and LSI+61o 303
1997
We present the results of a multiwavelength monitoring campaign targeting the gamma-ray source 2CG 135+1 in an attempt to confirm the association of this object with the radio/Be/X-ray binary system LSI +61o 303. The campaign included simultaneous radio, optical, infrared, and hard x-ray/gamma-ray observations carried out with a variety of instruments, covering (not continously) almost three binary cycles of LSI +61o 303 during the period April-July 1994. Three separate OSSE observations of the gamma-ray source were carried out, covering different phases of the radio lightcurve. Hard X-ray/gamma-ray emission was detected from the direction of 2CG 135+1 during the first of these OSSE observa…
The Cryogenic AntiCoincidence Detector Project for ATHENA+: An Overview Up to the Present Status
2014
ATHENA+ is a space mission proposal for the next ESA L2-L3 slot. One of the focal plane instruments is the X-ray integral field unit (X-IFU) working in the energy range 0.3–10 keV. It is a multi-array based on TES detectors aimed at characterizing faint or diffuse sources (e.g. WHIM or galaxy outskirt). The X-IFU will be able to achieve the required sensitivity if a low background is guaranteed. The studies performed by GEANT4 simulations depict a scenario where the use of an active anticoincidence (AC) is mandatory to reduce the background expected in L2 orbit down to the goal level of 0.005 cts cm $$^{-2}$$ s $$^{-1}$$ keV $$^{-1}$$ . This is possible using a cryogenic anticoincidence (…
a1(1420) peak as the πf0(980) decay mode of the a1(1260)
2016
We study the decay mode of the ${a}_{1}(1260)$ into a ${\ensuremath{\pi}}^{+}$ in $p$ wave and the ${f}_{0}(980)$ that decays into ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ in $s$ wave. The mechanism proceeds via a triangular mechanism where the ${a}_{1}(1260)$ decays into ${K}^{*}\overline{K}$, the ${K}^{*}$ decays to an external ${\ensuremath{\pi}}^{+}$ and an internal $K$ that fuses with the $\overline{K}$ producing the ${f}_{0}(980)$ resonance. The mechanism develops a singularity at a mass of the ${a}_{1}(1260)$ around 1420 MeV, producing a peak in the cross section of the $\ensuremath{\pi}p$ reaction, used to generate the mesonic final state, which provides a natural…
Identification of Bending Modes of Vibration in Rails by a Laser Doppler Vibrometer on a Moving Platform
2020
This paper introduces a method to identify the bending modes of vibration of railway tracks by using a laser Doppler vibrometer (LDV) mounted on a moving platform. Two sets of experiments were conducted at Transportation Technology Center Inc. (TTCI) in Pueblo Colorado, in order to validate the proposed method. First, the bending vibration modes were identified using the signals collected from a rail span (rail section between two consecutive sleepers) by accelerometers under moving car excitation. Then, vibration measurements from rail spans were obtained by using an LDV mounted on the moving railcar. All tests were carried out at four different rail car speeds: 8 km/h (5 mph), 16 km/h (10…
Studying endocytosis in space and time by means of temporal Boolean models
2006
Endocytosis is a process by which cells carry traffic from the extracellular space into various intracellular compartments. Visualization of fluorescently tagged clathrin proteins (mediators of endocytosis) allows us to image endocytosis in real time. When imaging the plasma membrane, areas of fluorescence generated by different endocytic processes overlap spatially and temporally, forming random clumps. Here, a sequence of segmented clathrin spots is considered a realization of a non-isotropic 3D Boolean model. Estimates of the intensity, the mean perimeter and the density function of the durations of endocytic events are obtained.
Measurement of the Spectral Shape of the β -Decay of Xe137 to the Ground State of Cs137 in EXO-200 and Comparison with Theory
2020
We report on a comparison between the theoretically predicted and experimentally measured spectra of the first-forbidden nonunique β-decay transition ^{137}Xe(7/2^{-})→^{137}Cs(7/2^{+}). The experimental data were acquired by the EXO-200 experiment during a deployment of an AmBe neutron source. The ultralow background environment of EXO-200, together with dedicated source deployment and analysis procedures, allowed for collection of a pure sample of the decays, with an estimated signal to background ratio of more than 99 to 1 in the energy range from 1075 to 4175 keV. In addition to providing a rare and accurate measurement of the first-forbidden nonunique β-decay shape, this work constitut…
The Cryogenic Anticoincidence Detector for ATHENA-XMS
2012
The TES cryogenic detectors, due to their high spectral resolution and imaging capability in the soft X-ray domain, are the reference devices for the next proposed space missions whose aims are to characterize the spectra of faint or diffuse sources. ATHENA is the re-scoped IXO mission, and one of its focal plane instrument is the X-ray Microcalorimeter Spectrometer (XMS) working in the energy range 0.3-10 keV. XMS will be able to achieve the proposed scientific goals if a background lower than 0.02 cts/cm2/s/keV is guaranteed. The studies performed by GEANT4 simulations depict a scenario where it is mandatory to use an active Anti-Coincidence (AC) to reduce the expected background in the L…