991 research outputs found
On the Sensitivity of a Hollow Sphere as a Multi-modal Resonant Gravitational Wave Detector
We present a numerical analysis to simulate the response of a spherical
resonant gravitational wave detector and to compute its sensitivity. Under the
assump- tion of optimal filtering, we work out the sensitivity curve for a
sphere first taking into account only a single transducer, and then using a
coherent analysis of the whole set of transducers.Comment: 24 pages, 11 figures, published versio
Sensitivity of the spherical gravitational wave detector MiniGRAIL operating at 5 K
We present the performances and the strain sensitivity of the first spherical
gravitational wave detector equipped with a capacitive transducer and read out
by a low noise two-stage SQUID amplifier and operated at a temperature of 5 K.
We characterized the detector performance in terms of thermal and electrical
noise in the system output sygnal. We measured a peak strain sensitivity of
at 2942.9 Hz. A strain sensitivity of better than
has been obtained over a bandwidth of 30 Hz. We expect
an improvement of more than one order of magnitude when the detector will
operate at 50 mK. Our results represent the first step towards the development
of an ultracryogenic omnidirectional detector sensitive to gravitational
radiation in the 3kHz range.Comment: 8 pages, 5 figures, submitted to Physical Review
Optimising the multiplex factor of the frequency domain multiplexed readout of the TES-based microcalorimeter imaging array for the X-IFU instrument on the Athena Xray observatory
Athena is a space-based X-ray observatory intended for exploration of the hot
and energetic universe. One of the science instruments on Athena will be the
X-ray Integrated Field Unit (X-IFU), which is a cryogenic X-ray spectrometer,
based on a large cryogenic imaging array of Transition Edge Sensors (TES) based
microcalorimeters operating at a temperature of 100mK. The imaging array
consists of 3800 pixels providing 2.5 eV spectral resolution, and covers a
field of view with a diameter of of 5 arc minutes. Multiplexed readout of the
cryogenic microcalorimeter array is essential to comply with the cooling power
and complexity constraints on a space craft. Frequency domain multiplexing has
been under development for the readout of TES-based detectors for this purpose,
not only for the X-IFU detector arrays but also for TES-based bolometer arrays
for the Safari instrument of the Japanese SPICA observatory. This paper
discusses the design considerations which are applicable to optimise the
multiplex factor within the boundary conditions as set by the space craft. More
specifically, the interplay between the science requirements such as pixel
dynamic range, pixel speed, and cross talk, and the space craft requirements
such as the power dissipation budget, available bandwidth, and electromagnetic
compatibility will be discussed
Lactobacillus paracasei A13 and high-pressure homogenization stress response
Sub-lethal high-pressure homogenization treatments applied to Lactobacillus paracasei A13 demonstrated to be a useful strategy to enhance technological and functional properties without detrimental effects on the viability of this strain. Modification of membrane fatty acid composition is reported to be the main regulatory mechanisms adopted by probiotic lactobacilli to counteract high-pressure stress. This work is aimed to clarify and understand the relationship between the modification of membrane fatty acid composition and the expression of genes involved in fatty acid biosynthesis in Lactobacillus paracasei A13, before and after the application of different sub-lethal hyperbaric treatments. Our results showed that Lactobacillus paracasei A13 activated a series of reactions aimed to control and stabilize membrane fluidity in response to high-pressure homogenization treatments. In fact, the production of cyclic fatty acids was counterbalanced by the unsaturation and elongation of fatty acids. The gene expression data indicate an up-regulation of the genes accA, accC, fabD, fabH and fabZ after high-pressure homogenization treatment at 150 and 200 MPa, and of fabK and fabZ after a treatment at 200 MPa suggesting this regulation of the genes involved in fatty acids biosynthesis as an immediate response mechanism adopted by Lactobacillus paracasei A13 to high-pressure homogenization treatments to balance the membrane fluidity. Although further studies should be performed to clarify the modulation of phospholipids and glycoproteins biosynthesis since they play a crucial role in the functional properties of the probiotic strains, this study represents an important step towards understanding the response mechanisms of Lactobacillus paracasei A13 to sub-lethal high-pressure homogenization treatments
Proximity effect model for x-ray transition edge sensors
Transition Edge Sensors are ultra-sensitive superconducting detectors with
applications in many areas of research, including astrophysics. The device
consists of a superconducting thin film, often with additional normal metal
features, held close to its transition temperature and connected to two
superconducting leads of a higher transition temperature. There is currently no
way to reliably assess the performance of a particular device geometry or
material composition without making and testing the device. We have developed a
proximity effect model based on the Usadel equations to predict the effects of
device geometry and material composition on sensor performance. The model is
successful in reproducing I-V curves for two devices currently under study. We
use the model to suggest the optimal size and geometry for TESs, considering
how small the devices can be made before their performance is compromised. In
the future, device modelling prior to manufacture will reduce the need for
time-consuming and expensive testing.This work was partly supported by ESA CTP contract with No. 4000114932/15/NL/BW and EU H2020 AHEAD program
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