415 research outputs found
Proof-of-principle demonstration of vertical gravity gradient measurement using a single proof mass double-loop atom interferometer
We demonstrate a proof-of-principle of direct Earth gravity gradient
measurement with an atom interferometer-based gravity gradiomter using a single
proof mass of cold 87 rubidium atoms. The atomic gradiometer is implemented in
the so-called double-loop configuration, hence providing a direct gravity
gradient dependent phase shift insensitive do DC acceleration and constant
rotation rate. The atom interferometer (AI) can be either operated as a
gravimeter or a gradiomter by simply adding an extra Raman -pulse. We
demonstrate gravity gradient measurements first using a vibration isolation
platform and second without seismic isolation using the correlation between the
AI signal and the vibration signal measured by an auxilliary classical
accelerometer. The simplicity of the experimental setup (a single atomic source
and unique detection) and the immunity of the AI to rotation-induced contrast
loss, make it a good candidate for onboard gravity gradient measurements.Comment: 11 pages, 7 figure
New concepts of inertial measurements with multi-species atom interferometry
In the field of cold atom inertial sensors, we present and analyze innovative
configurations for improving their measurement range and sensitivity,
especially attracting for onboard applications. These configurations rely on
multi-species atom interferometry, involving the simultaneous manipulation of
different atomic species in a unique instrument to deduce inertial
measurements. Using a dual-species atom accelerometer manipulating
simultaneously both isotopes of rubidium, we report a preliminary experimental
realization of original concepts involving the implementation of two atom
interferometers first with different interrogation times and secondly in phase
quadrature. These results open the door to a new generation of atomic sensors
relying on high performance multi-species atom interferometric measurements
Light transport in cold atoms: the fate of coherent backscattering in the weak localization regime
The recent observation of coherent backscattering (CBS) of light by atoms has
emphasized the key role of the velocity spread and of the quantum internal
structure of the atoms. Firstly, using highly resonant scatterers imposes very
low temperatures of the disordered medium in order to keep the full contrast of
the CBS interference. This criterion is usually achieved with standard laser
cooling techniques. Secondly, a non trivial internal atomic structure leads to
a dramatic decrease of the CBS contrast. Experiments with Rubidium atoms (with
a non trivial internal structure) and with Strontium (with the simplest
possible internal structure) show this behaviour and confirm theoretical
calculations
Saturation induced coherence loss in coherent backscattering of light
We use coherent backscattering (CBS) of light by cold Strontium atoms to
study the mutual coherence of light waves in the multiple scattering regime. As
the probe light intensity is increased, the atomic optical transition starts to
be saturated. Nonlinearities and inelastic scattering then occur. In our
experiment, we observe a strongly reduced enhancement factor of the coherent
backscattering cone when the intensity of the probe laser is increased,
indicating a partial loss of coherence in multiple scattering
Coffee and risk of type 2 diabetes
Type 2 diabetes is one of the diseases that largely determined by lifestyle factors. Coffee is one of the most consumed beverages in the world and recently released data suggest the effects of coffee consumption on type 2 diabetes. The objective of the present study was to evaluate the effects of habitual coffee consumption on various aspects of type 2 diabetes and its most common complications.
This study is part of the national FINRISK studies. Baseline surveys were carried out between 1972 and 1997. The surveys covered two eastern regions in 1972 and 1977, but were expanded to include a third region in southwestern Finland in 1982, 1987, 1992, and 1997. The Helsinki capital area was included in the survey in 1992 and 1997 and the Oulu province, in northern Finland, in 1997. Each survey was drawn from an independent random sample of the national register of subjects aged 25-64. In 1997, an additional sample of subjects aged 65-74 was conducted. The blood pressure, weight, and height of subjects were measured. By using self-administered questionnaires data were collected on medical history, socioeconomic factors, physical activity, smoking habits, and alcohol, coffee, and tea consumption.
Higher coffee consumption was associated with higher body mass index, occupational physical activity and cigarette smoking, and lower blood pressure, education level, leisure time physical activity, tea consumption and alcohol use. Age, body mass index, systolic blood pressure and current smoking were positively associated with the risk of type 2 diabetes, however, education, and occupational, commuting and leisure time physical activity were inversely associated.
The significant inverse association between coffee consumption and the risk of type 2 diabetes was found in both sexes but the association was stronger in women. Coffee consumption was significantly and inversely associated with fasting glucose, 2-hour plasma glucose, fasting insulin, impaired fasting glucose, impaired glucose regulation, and hyperinsulinemia among both men and women and with isolated impaired glucose tolerance among women.
Serum gamma-glutamyltransferase modified the association between coffee consumption and incident diabetes. Among subjects with high serum -glutamyltransferase (>75th percentile), coffee consumption showed an inverse association for women, as well as men and women combined. An inverse association also occurred between coffee consumption and the risk of total, cardiovascular disease, and coronary heart disease mortality among patients with type 2 diabetes.
The results of this study showed that habitual coffee consumption may be associated with a reduced risk of type 2 diabetes. Coffee consumption may have some effects on several markers of glycemia, and may lower the incident of type 2 diabetes in high normal serum -glutamyltransferase levels. Total, cardiovascular disease, and coronary heart disease mortality rate among subjects with type 2 diabetes may also be reduced by coffee consumption.Ei julkaistu
Local gravity measurement with the combination of atom interferometry and Bloch oscillations
We present a local measurement of gravity combining Bloch oscillations and
atom interferometry. With a falling distance of 0.8 mm, we achieve a
sensitivity of 2x10-7 g with an integration time of 300 s. No bias associated
with the Bloch oscillations has been measured. A contrast decay with Bloch
oscillations has been observed and attributed to the spatial quality of the
laser beams. A simple experimental configuration has been adopted where a
single retro-reflected laser beam is performing atoms launch, stimulated Raman
transitions and Bloch oscillations. The combination of Bloch oscillations and
atom interferometry can thus be realized with an apparatus no more complex than
a standard atomic gravimeter
Doppler cooling to the recoil limit using sharp atomic transitions
In this paper, we develop an analytical approach to Doppler cooling of atoms
by one- or two-photon transitions when the natural width of the excited level
is so small that the process leads to a Doppler temperature comparable to the
recoil temperature. A ``quenching'' of the sharp line is introduced in order to
allow control of the time scale of the problem. In such limit, the usual
Fokker-Planck equation does not correctly describe the cooling process. We
propose a generalization of the Fokker-Planck equation and derive a new model
which is able to reproduce correctly the numerical results, up to the recoil
limit. Two cases of practical interest, one-photon Doppler cooling of strontium
and two-photon Doppler cooling of hydrogen are considered.Comment: 5 pages, RevTex 4, submitted to JOSA B (special issue "laser cooling
of atoms"
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