1,271 research outputs found
Assessment method for photo-induced waveguides
A method to probe the guiding characteristics of waveguides formed in
real-time is proposed and evaluated. It is based on the analysis of the time
dependent light distribution observed at the exit face of the waveguide while
progressively altering its index profile and probed by a large diameter optical
beam. A beam propagation method is used to model the observed dynamics. The
technique is applied to retrieve the properties of soliton-induced waveguides
Comparación de tests: Cooper y Rockport
La presente investigación compara los tests de Cooper y Rockport según las variables frecuencia cardiaca (FC), consumo máximo de oxígeno (VO2máx.), valoración del esfuerzo percibido y distancia ¿ tiempo. La muestra se corresponde con 27 alumnos de 2º de ESO de un instituto de Madrid. El registro de FC se hizo a través de pulsómetros en periodos de 60 segundos. Se constataron para el test de Cooper, FC máx > 200 lat.· min-1 en el 66,6 % (sexo femenino). El 100 % (sexo masculino) registró FC > 200 lat.· min-1. En el test de Rockport los valores de FC fueron inferiores; el 40 % (sexo femenino) registró FC > 200 lat.· min-1 y el 44,4% (sexo masculino) observó una FC > 200 lat.· min-1. Cinco sujetos superaron su FC máxima teórica. Se constata diferencias significativas en la valoración de la escala del esfuerzo percibido entre los tests (sexo femenino) y en la valoración del VO2máx. en ambos sexos
Roles of resonance and dark irradiance for infrared photorefractive self-focusing and solitons in bi-polar InP:Fe
This paper shows experimental evidence of photorefractive steady state
self-focusing in InP:Fe for a wide range of intensities, at both 1.06 and
1.55m. To explain those results, it is shown that despite the bi-polar
nature of InP:Fe where one photocarrier and one thermal carrier are to be
considered, the long standing one photocarrier model for photorefractive
solitons can be usefully applied. The relationship between the dark irradiance
stemming out of this model and the known resonance intensity is then discussed
Locking Local Oscillator Phase to the Atomic Phase via Weak Measurement
We propose a new method to reduce the frequency noise of a Local Oscillator
(LO) to the level of white phase noise by maintaining (not destroying by
projective measurement) the coherence of the ensemble pseudo-spin of atoms over
many measurement cycles. This scheme uses weak measurement to monitor the phase
in Ramsey method and repeat the cycle without initialization of phase and we
call, "atomic phase lock (APL)" in this paper. APL will achieve white phase
noise as long as the noise accumulated during dead time and the decoherence are
smaller than the measurement noise. A numerical simulation confirms that with
APL, Allan deviation is averaged down at a maximum rate that is proportional to
the inverse of total measurement time, tau^-1. In contrast, the current atomic
clocks that use projection measurement suppress the noise only down to the
level of white frequency, in which case Allan deviation scales as tau^-1/2.
Faraday rotation is one of the possible ways to realize weak measurement for
APL. We evaluate the strength of Faraday rotation with 171Yb+ ions trapped in a
linear rf-trap and discuss the performance of APL. The main source of the
decoherence is a spontaneous emission induced by the probe beam for Faraday
rotation measurement. One can repeat the Faraday rotation measurement until the
decoherence become comparable to the SNR of measurement. We estimate this
number of cycles to be ~100 cycles for a realistic experimental parameter.Comment: 18 pages, 7 figures, submitted to New Journal of Physic
Optical measurement of heteronuclear cross-relaxation interactions in Tm:YAG
We investigate cross-relaxation interactions between Tm and Al in Tm:YAG
using two optical methods: spectral holeburning and stimulated echoes. These
interactions lead to a reduction in the hyperfine lifetime at magnetic fields
that bring the Tm hyperfine transition into resonance with an Al transition. We
develop models for measured echo decay curves and holeburning spectra near a
resonance, which are used to show that the Tm-Al interaction has a resonance
width of 10~kHz and reduces the hyperfine lifetime to 0.5 ms. The antihole
structure is consistent with an interaction dominated by the Al nearest
neighbors at 3.0 Angstroms, with some contribution from the next nearest
neighbors at 3.6 Angstroms.Comment: 13 pages, 9 figure
Apparition d'une résistance au Temephos dans le complexe SIMULIUM DAMNOSUM (S. SQUAMOSUM) sur le site du barrage de Song-Loulou (Sanaga maritime, Cameroun)
- …