510 research outputs found
Long Distance Transport of Ultracold Atoms using a 1D optical lattice
We study the horizontal transport of ultracold atoms over macroscopic
distances of up to 20 cm with a moving 1D optical lattice. By using an optical
Bessel beam to form the optical lattice, we can achieve nearly homogeneous
trapping conditions over the full transport length, which is crucial in order
to hold the atoms against gravity for such a wide range. Fast transport
velocities of up to 6 m/s (corresponding to about 1100 photon recoils) and
accelerations of up to 2600 m/s2 are reached. Even at high velocities the
momentum of the atoms is precisely defined with an uncertainty of less than one
photon recoil. This allows for construction of an atom catapult with high
kinetic energy resolution, which might have applications in novel collision
experiments.Comment: 15 pages, 8 figure
A relativistic study of Bessel beams
We present a fully relativistic analysis of Bessel beams revealing some
noteworthy features that are not explicit in the standard description. It is
shown that there is a reference frame in which the field takes a particularly
simple form, the wave appearing to rotate in circles. The concepts of
polarization and angular momentum for Bessel beams is also reanalyzed.Comment: 11 pages, 2 fig
Association of FTO With Obesity-Related Traits in the Cebu Longitudinal Health and Nutrition Survey (CLHNS) Cohort
OBJECTIVE—The underlying genetic component of obesity-related traits is not well understood, and there is limited evidence to support genetic association shared across multiple studies, populations, and environmental contexts. The present study investigated the association between candidate variants and obesity-related traits in a sample of 1,886 adult Filipino women from the Cebu Longitudinal Health and Nutrition Survey (CLHNS) cohort
Embryonic Lethality, Liver Degeneration, and Impaired NF-κB Activation in IKK-β-Deficient Mice
AbstractIκB kinase-α and -β (IKK-α and IKK-β), the catalytic subunits of the IKK complex, phosphorylate IκB proteins on specific serine residues, thus targeting IκB for degradation and activating the transcription factor NF-κB. To elucidate the in vivo function of IKK-β, we generated IKK-β-deficient mice. The homozygous mouse embryo dies at ∼14.5 days of gestation due to liver degeneration and apoptosis. IKK-β-deficient embryonic fibroblasts have both reduced basal NF-κB activity and impaired cytokine-induced NF-κB activation. Similarly, basal and cytokine-inducible kinase activities of the IKK complex are greatly reduced in IKK-β-deficient cells. These results indicate that IKK-β is crucial for liver development and regulation of NF-κB activity and that IKK-α can only partially compensate for the loss of IKK-β
Adjusting bone mass for differences in projected bone area and other confounding variables: an allometric perspective.
The traditional method of assessing bone mineral density (BMD; given by bone mineral content [BMC] divided by projected bone area [Ap], BMD = BMC/Ap) has come under strong criticism by various authors. Their criticism being that the projected bone "area" (Ap) will systematically underestimate the skeletal bone "volume" of taller subjects. To reduce the confounding effects of bone size, an alternative ratio has been proposed called bone mineral apparent density [BMAD = BMC/(Ap)3/2]. However, bone size is not the only confounding variable associated with BMC. Others include age, sex, body size, and maturation. To assess the dimensional relationship between BMC and projected bone area, independent of other confounding variables, we proposed and fitted a proportional allometric model to the BMC data of the L2-L4 vertebrae from a previously published study. The projected bone area exponents were greater than unity for both boys (1.43) and girls (1.02), but only the boy's fitted exponent was not different from that predicted by geometric similarity (1.5). Based on these exponents, it is not clear whether bone mass acquisition increases in proportion to the projected bone area (Ap) or an estimate of projected bone volume (Ap)3/2. However, by adopting the proposed methods, the analysis will automatically adjust BMC for differences in projected bone size and other confounding variables for the particular population being studied. Hence, the necessity to speculate as to the theoretical value of the exponent of Ap, although interesting, becomes redundant
Nonlinear vortex light beams supported and stabilized by dissipation
We describe nonlinear Bessel vortex beams as localized and stationary
solutions with embedded vorticity to the nonlinear Schr\"odinger equation with
a dissipative term that accounts for the multi-photon absorption processes
taking place at high enough powers in common optical media. In these beams,
power and orbital angular momentum are permanently transferred to matter in the
inner, nonlinear rings, at the same time that they are refueled by spiral
inward currents of energy and angular momentum coming from the outer linear
rings, acting as an intrinsic reservoir. Unlike vortex solitons and dissipative
vortex solitons, the existence of these vortex beams does not critically depend
on the precise form of the dispersive nonlinearities, as Kerr self-focusing or
self-defocusing, and do not require a balancing gain. They have been shown to
play a prominent role in "tubular" filamentation experiments with powerful,
vortex-carrying Bessel beams, where they act as attractors in the beam
propagation dynamics. Nonlinear Bessel vortex beams provide indeed a new
solution to the problem of the stable propagation of ring-shaped vortex light
beams in homogeneous self-focusing Kerr media. A stability analysis
demonstrates that there exist nonlinear Bessel vortex beams with single or
multiple vorticity that are stable against azimuthal breakup and collapse, and
that the mechanism that renders these vortexes stable is dissipation. The
stability properties of nonlinear Bessel vortex beams explain the experimental
observations in the tubular filamentation experiments.Comment: Chapter of boo
Generation of nearly nondiffracting Bessel beams with a Fabry–Perot interferometer
A new concept for generating zero-order Bessel beams was studied theoretically. The spatial intensity distribution was calculated numerically using a wave optics model. Approximate analytical expressions were derived to describe the radial intensity distribution in planes perpendicular to the optical axis of an imaging
lens.Texas InstrumentsNational Science FoundationOTKA Foundation of the Hungarian Academy of Science
Decline in Physical Fitness From Childhood to Adulthood Associated With Increased Obesity and Insulin Resistance in Adults
To examine how fitness in both childhood and adulthood is associated with adult obesity and insulin resistance. A prospective cohort study set in Australia in 2004-2006 followed up a cohort of 647 adults who had participated in the Australian Schools Health and Fitness Survey in 1985 and who had undergone anthropometry and cardiorespiratory fitness assessment during the survey. Outcome measures were insulin resistance and obesity, defined as a homeostasis model assessment index above the 75th sex-specific percentile and BMI ≥30 kg/m^sup 2^, respectively. Lower levels of child cardiorespiratory fitness were associated with increased odds of adult obesity (adjusted odds ratio [OR] per unit decrease 3.0 [95% CI 1.6- 5.6]) and insulin resistance (1.7 [1.1-2.6]). A decline in fitness level between childhood and adulthood was associated with increased obesity (4.5 [2.6-7.7]) and insulin resistance (2.1 [1.5- 2.9]) per unit decline. A decline in fitness from childhood to adulthood, and by inference a decline in physical activity, is associated with obesity and insulin resistance in adulthood. Programs aimed at maintaining high childhood physical activity levels into adulthood may have potential for reducing the burden of obesity and type 2 diabetes in adults.<br /
X-wave mediated instability of plane waves in Kerr media
Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e.
non-dispersive and non-diffractive pulsed beams) that get amplified along
propagation. This effect can be considered a form of conical emission (i.e.
spatio-temporal modulational instability), and can be used as a key for the
interpretation of the out of axis energy emission in the splitting process of
focused pulses in normally dispersive materials. A new class of spatio-temporal
localized wave patterns is identified. X-waves instability, and nonlinear
X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure
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