1,333 research outputs found
Theoretical tools for atom laser beam propagation
We present a theoretical model for the propagation of non self-interacting
atom laser beams. We start from a general propagation integral equation, and we
use the same approximations as in photon optics to derive tools to calculate
the atom laser beam propagation. We discuss the approximations that allow to
reduce the general equation whether to a Fresnel-Kirchhoff integral calculated
by using the stationary phase method, or to the eikonal. Within the paraxial
approximation, we also introduce the ABCD matrices formalism and the beam
quality factor. As an example, we apply these tools to analyse the recent
experiment by Riou et al. [Phys. Rev. Lett. 96, 070404 (2006)]
Tuberculosis treatment in a refugee and migrant population: 20 years of experience on the Thai-Burmese border.
Although tuberculosis (TB) is a curable disease, it remains a major global health problem and an important cause of morbidity and mortality among vulnerable populations, including refugees and migrants
Optical parametric oscillation with distributed feedback in cold atoms
There is currently a strong interest in mirrorless lasing systems, in which
the electromagnetic feedback is provided either by disorder (multiple
scattering in the gain medium) or by order (multiple Bragg reflection). These
mechanisms correspond, respectively, to random lasers and photonic crystal
lasers. The crossover regime between order and disorder, or correlated
disorder, has also been investigated with some success. Here, we report
one-dimensional photonic-crystal lasing (that is, distributed feedback lasing)
with a cold atom cloud that simultaneously provides both gain and feedback. The
atoms are trapped in a one-dimensional lattice, producing a density modulation
that creates a strong Bragg reflection with a small angle of incidence. Pumping
the atoms with auxiliary beams induces four-wave mixing, which provides
parametric gain. The combination of both ingredients generates a mirrorless
parametric oscillation with a conical output emission, the apex angle of which
is tunable with the lattice periodicity
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Short term bioassay and bioassay chemistry of materials related to synthetic fossil fuels
An abstract was prepared for one paper. Abstracts of the five additional papers appeared previously in ERA
Developmental regulation of neuraminidase-sensitive lectin-binding glycoproteins during myogenesis of rat L6 myoblasts
Устройство для перемещения датчиков в магнитном поле малогабаритного бетатрона
Рассматривается возможность увеличения точности измерений характеристик магнитного поля посредством более точной установки датчиков в исследуемой точке
Who I Am: The Meaning of Early Adolescents’ Most Valued Activities and Relationships, and Implications for Self-Concept Research
Self-concept research in early adolescence typically measures young people’s self-perceptions of competence in specific, adult-defined domains. However, studies have rarely explored young people’s own views of valued self-concept factors and their meanings. For two major self domains, the active and the social self, this mixed-methods study identified factors valued most by 526 young people from socioeconomically diverse backgrounds in Ireland (10-12 years), and explored the meanings associated with these in a stratified subsample (n = 99). Findings indicate that self-concept scales for early adolescence omit active and social self factors and meanings valued by young people, raising questions about content validity of scales in these domains. Findings also suggest scales may under-represent girls’ active and social selves; focus too much on some school-based competencies; and, in omitting intrinsically salient self domains and meanings, may focus more on contingent (extrinsic) rather than true (intrinsic) self-esteem
L\'evy flights of photons in hot atomic vapours
Properties of random and fluctuating systems are often studied through the
use of Gaussian distributions. However, in a number of situations, rare events
have drastic consequences, which can not be explained by Gaussian statistics.
Considerable efforts have thus been devoted to the study of non Gaussian
fluctuations such as L\'evy statistics, generalizing the standard description
of random walks. Unfortunately only macroscopic signatures, obtained by
averaging over many random steps, are usually observed in physical systems. We
present experimental results investigating the elementary process of anomalous
diffusion of photons in hot atomic vapours. We measure the step size
distribution of the random walk and show that it follows a power law
characteristic of L\'evy flights.Comment: This final version is identical to the one published in Nature
Physic
A slow gravity compensated Atom Laser
We report on a slow guided atom laser beam outcoupled from a Bose-Einstein
condensate of 87Rb atoms in a hybrid trap. The acceleration of the atom laser
beam can be controlled by compensating the gravitational acceleration and we
reach residual accelerations as low as 0.0027 g. The outcoupling mechanism
allows for the production of a constant flux of 4.5x10^6 atoms per second and
due to transverse guiding we obtain an upper limit for the mean beam width of
4.6 \mu\m. The transverse velocity spread is only 0.2 mm/s and thus an upper
limit for the beam quality parameter is M^2=2.5. We demonstrate the potential
of the long interrogation times available with this atom laser beam by
measuring the trap frequency in a single measurement. The small beam width
together with the long evolution and interrogation time makes this atom laser
beam a promising tool for continuous interferometric measurements.Comment: 7 pages, 8 figures, to be published in Applied Physics
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