158 research outputs found
High-impedence NbSi TES sensors for studying the cosmic microwave background radiation
Precise measurements of the cosmic microwave background (CMB) are crucial in
cosmology, because any proposed model of the universe must account for the
features of this radiation. Of all CMB measurements that the scientific
community has not yet been able to perform, the CMB B-mode polarization is
probably the most challenging from the instrumental point of view. The
signature of primordial gravitational waves, which give rise to a B-type
polarization, is one of the goals in cosmology today and amongst the first
objectives in the field. For this purpose, high-performance low-temperature
bolometric cameras, made of thousands of pixels, are currently being developed
by many groups, which will improve the sensitivity to B-mode CMB polarization
by one or two orders of magnitude compared to the Planck satellite HFI
detectors. We present here a new bolometer structure that is able to increase
the pixel sensitivities and to simplify the fabrication procedure. This
innovative device replaces delicate membrane-based structures and eliminates
the mediation of phonons: the incoming energy is directly captured and measured
in the electron bath of an appropriate sensor and the thermal decoupling is
achieved via the intrinsic electron-phonon decoupling of the sensor at very low
temperature. Reported results come from a 204-pixel array of NbSi
transition edge sensors with a meander structure fabricated on a 2-inch silicon
wafer using electron-beam co-evaporation and a cleanroom lithography process.
To validate the application of this device to CMB measurements, we have
performed an optical calibration of our sample in the focal plane of a dilution
cryostat test bench. We have demonstrated a light absorption close to 20% and
an NEP of about 7 W/, which is highly encouraging
given the scope for improvement in this type of detectors.Comment: 6 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1005.0555 by other author
Are stress and mixed urinary incontinence associated with impaired executive control in community-dwelling older women?
Objectives: To assess whether stress or mixed urinary incontinence (UI) is associated with deficits in executive functioning among community-dwelling women. Design: An observational study comparing the performance, using multivariate analyses of variance (MANOVAs) and Bonferroni post hoc test, of continent women and women with stress or mixed UI during executive control tasks. Setting: The research center of the Institut universitaire de gériatrie de Montréal. Participants: One hundred and fifty-five community-dwelling women aged 60 and older participated in the study. Measurements: Based on the Urogenital Distress Inventory (UDI), participants were split into three groups: 35 continent women, 43 women with stress UI, and 78 women with mixed UI. Participants completed a battery of neuropsychological tests and a computerized dual-task test. Results: Women with mixed UI showed poorer performances than continent and stress UI women in executive control functions. Deficits were specific to tests involving switching and sharing/dividing attention between two tasks. Conclusion: Results of this study suggest that mixed UI can be associated with executive control deficits in community-dwelling older women. Future intervention studies in the treatment of UI should take the higher risk of an executive control deficit in women with UI under consideration
Tunable Superconducting Properties of a-NbSi Thin Films and Application to Detection in Astrophysics
We report on the superconducting properties of amorphous NbxSi1-x thin films.
The normal-state resistance and critical temperatures can be separately
adjusted to suit the desired application. Notably, the relatively low
electron-phonon coupling of these films makes them good candidates for an "all
electron bolometer" for Cosmological Microwave Background radiation detection.
Moreover, this device can be made to suit both high and low impedance readouts
Spontaneous voltage peaks in superconducting Nb channels without engineered asymmetry
Rectification effects in solid-state devices are a consequence of
nonreciprocal transport properties. This phenomenon is usually observed in
systems with broken inversion symmetry. In most instances, nonreciprocal
transport arises in the presence of an applied magnetic field and the rectified
signal has an antisymmetric dependence on the field. We have observed
rectification of environmental electromagnetic fluctuations in plain Nb
channels without any asymmetry in design, leading to spontaneous voltage peaks
at the superconducting transition. The signal is symmetric in the magnetic
field and appears even without an applied field at the critical temperature.
This is indicative of an unconventional mechanism of nonreciprocal transport
resulting from a spontaneous breaking of inversion symmetry
Active Thermal Shearography and Infrared Thermography Applied to NDT of Reinforced Concrete Structure by Glued CFRP
International audienceThis research paper presents the study of thermography and shearography to evaluate CFRP reinforcement of concrete structures. The study explores the strengths and weaknesses of both non-destructive-testing (NDT) methods. It will be shown that by coupling the methods, the detection is more reliable and the defect evaluation more thorough as both the thermal and thermo mechanical properties are tested. Once the core theoretical concept regarding both methods is presented, the viability is demonstrated in the experimentation part of this study. With the experimental results confirming the feasibility of the coupling of both methods, the numerical model conceived allow to better conduct analysis that are not otherwise possible with the experimental results
Comparison between SPT and PT for defect characterization of CFRP plates glued on concrete or wood structures using optical active infrared thermography
International audienceThe objectives of the study summarized hereafter are to compare square pulse and pulsed thermography fordefect detection and characterization of CFRP plates used as structural reinforcement in Civil Engineering applications.Image processing and an inverse method coupled with thermal quadrupoles model are also studied
- …