3,996 research outputs found
Optical cuff for optogenetic control of the peripheral nervous system
OBJECTIVE: Nerves in the peripheral nervous system (PNS) contain axons with specific motor, somatosensory and autonomic functions. Optogenetics offers an efficient approach to selectively activate axons within the nerve. However, the heterogeneous nature of nerves and their tortuous route through the body create a challenging environment to reliably implant a light delivery interface. APPROACH: Here, we propose an optical peripheral nerve interface – an optocuff -, so that optogenetic modulation of peripheral nerves become possible in freely behaving mice. MAIN RESULTS: Using this optocuff, we demonstrate orderly recruitment of motor units with epineural optical stimulation of genetically targeted sciatic nerve axons, both in anaesthetized and in awake, freely behaving animals. Behavioural experiments and histology show the optocuff does not damage the nerve thus is suitable for long-term experiments. SIGNIFICANCE: These results suggest that the soft optocuff might be a straightforward and efficient tool to support more extensive study of the PNS using optogenetics
Characterization of integrated optics components for the second generation of VLTI instruments
Two of the three instruments proposed to ESO for the second generation
instrumentation of the VLTI would use integrated optics for beam combination.
Several design are studied, including co-axial and multi-axial recombination.
An extensive quantity of combiners are therefore under test in our
laboratories. We will present the various components, and the method used to
validate and compare the different combiners. Finally, we will discuss the
performances and their implication for both VSI and Gravity VLTI instruments.Comment: SPIE Astronomical Instrumentation 2008 in Marseille, France --
Equation (7) update
Importance of the Saharan heat low in controlling the North Atlantic free tropospheric humidity budget deduced from IASI <i>δ</i>D observations
The isotopic composition of water vapour in the North Atlantic free
troposphere is investigated with Infrared Atmospheric Sounding Interferometer
(IASI) measurements of the D ∕ H ratio (δD) above the ocean. We
show that in the vicinity of West Africa, the seasonality of δD is
particularly strong (130 ‰), which is related with the influence of
the Saharan heat low (SHL) during summertime. The SHL indeed largely
influences the dynamic in that region by producing deep turbulent mixing
layers, yielding a specific water vapour isotopic footprint. The influence of
the SHL on the isotopic budget is analysed on various time and space scales
and is shown to be large, highlighting the importance of the SHL dynamics on
the moistening and the HDO enrichment of the free troposphere over the North
Atlantic. The potential influence of the SHL is also investigated on the
inter-annual scale as we also report important variations in δD above
the Canary archipelago region. We interpret the variability in the
enrichment, using backward trajectory analyses, in terms of the ratio of air
masses coming from the North Atlantic and air masses coming from the African
continent. Finally, the interest of IASI high sampling capabilities is
further illustrated by presenting spatial distributions of δD and
humidity above the North Atlantic from which we show that the different
sources and dehydration pathways controlling the humidity can be disentangled
thanks to the added value of δD observations. More generally, our
results demonstrate the utility of δD observations obtained from the
IASI sounder to gain insight into the hydrological cycle processes in the
West African region
Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media
Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has
been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties
of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina
nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force
microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer
while stronger coupling is observed in the case of TbCo alloys.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535
Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media
Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has
been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties
of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina
nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force
microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer
while stronger coupling is observed in the case of TbCo alloys.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535
Initial experience with continuous intra-arterial fluorescent glucose monitoring in patients in the ICU following cardiac surgery
The Fringe Detection Laser Metrology for the GRAVITY Interferometer at the VLTI
Interferometric measurements of optical path length differences of stars over
large baselines can deliver extremely accurate astrometric data. The
interferometer GRAVITY will simultaneously measure two objects in the field of
view of the Very Large Telescope Interferometer (VLTI) of the European Southern
Observatory (ESO) and determine their angular separation to a precision of 10
micro arcseconds in only 5 minutes. To perform the astrometric measurement with
such a high accuracy, the differential path length through the VLTI and the
instrument has to be measured (and tracked since Earth's rotation will
permanently change it) by a laser metrology to an even higher level of accuracy
(corresponding to 1 nm in 3 minutes). Usually, heterodyne differential path
techniques are used for nanometer precision measurements, but with these
methods it is difficult to track the full beam size and to follow the light
path up to the primary mirror of the telescope. Here, we present the
preliminary design of a differential path metrology system, developed within
the GRAVITY project. It measures the instrumental differential path over the
full pupil size and up to the entrance pupil location. The differential phase
is measured by detecting the laser fringe pattern both on the telescopes'
secondary mirrors as well as after reflection at the primary mirror. Based on
our proposed design we evaluate the phase measurement accuracy based on a full
budget of possible statistical and systematic errors. We show that this
metrology design fulfills the high precision requirement of GRAVITY.Comment: Proc. SPIE in pres
Cross-validation of IASI/MetOp derived tropospheric δD with TES and ground-based FTIR observations
International audienceThe Infrared Atmospheric Sounding Interferometer (IASI) flying on-board MetOpA and MetOpB is able to capture fine isotopic variations of the HDO to H2O ratio (δD) in the troposphere. Such observations at the high spatio temporal resolution of the sounder are of great interest to improve our understanding of the mechanisms controlling humidity in the troposphere. In this study we aim to empirically assess the validity of our error estimation previously evaluated theoretically. To achieve this, we compare IASI δD retrieved profiles with other available profiles of δD, from the TES infrared sounder onboard AURA and from three ground-based FTIR stations produced within the MUSICA project: the NDACC (Network for the Detection of Atmospheric Composition Change) sites Kiruna and Izana, and the TCCON site Karlsruhe, which in addition to near-infrared TCCON spectra also records mid-infrared spectra. We describe the achievable level of agreement between the different retrievals and show that these theoretical errors are in good agreement with empirical differences. The comparisons are made at different locations from tropical to Arctic latitudes, above sea and above land. Generally IASI and TES are similarly sensitive to δD in the free troposphere which allows to compare their measurements directly. At tropical latitudes where IASI's sensitivity is lower than that of TES, we show that the agreement improves when taking into account the sensitivity of IASI in the TES retrieval. For the comparison IASI-FTIR only direct comparisons are performed because of similar sensitivities. We identify a quasi negligible bias in the free troposphere (−3‰) between IASI retrieved δD with the TES one, which are bias corrected, but an important with the ground-based FTIR reaching −47‰. We also suggest that model-satellite observations comparisons could be optimized with IASI thanks to its high spatial and temporal sampling
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