40 research outputs found
Symmetrical field effect and slow electron relaxation in granular aluminium
Conductivity and field effect measurements in thin insulating Al granular
films are reported. The occurrence of a symmetrical field effect and of very
slow conductance relaxations is demonstrated. They are identical to the
electron glassy behaviours already reported in insulating indium oxide thin
films. The results suggest that the phenomena are quite general. The study of
structurally discontinuous samples should help to understand the origin and
mechanism of the glassy behaviour
Electrical glassy behavior in granular aluminium thin films
We present new results obtained by field effect measurements on insulating
granular Al thin films. First, reproducible and stable conductance fluctuations
are seen in micron size samples as a function of gate voltage. The anomalous
field effect and its slow relaxation already known to exist in macroscopic
samples are shown to still exist in small samples and to have no influence on
the fluctuations pattern. Secondly, "true" aging is demonstrated, i.e. the
anomalous field effect relaxation depends on the time elapsed since the
cooling, the longer this time the longer it takes for the system to react to a
gate voltage change. Interpretations and implications of these findings are
discussed.Comment: 5th International Conference on Electronic Crystals (ECRYS),
Carg\`ese : France (2008
Screening and conductance relaxations in insulating granular aluminium thin films
We have recently found in insulating granular Al thin film a new experimental
feature (Delahaye et al., Phys. Rev. Lett. 106, 186602, 2011), namely the
existence of a conductance relaxation that is not sensitive to gate voltage
changes. This conductance relaxation is related to the existence of a
metallic-like screening in the film and can be used to estimate its
characteristic length scale. In the present paper, we give some experimental
details on how this feature was measured and present our first results on the
screening length temperature dependence.Comment: 14th Transport in interacting disordered systems (TIDS14) conference,
September 5-8 2011, Acre (Israel
Observation of thermally activated glassiness and memory dip in a-NbSi insulating thin films
We present electrical conductance measurements on amorphous NbSi insulating
thin films. These films display out-of equilibrium electronic features that are
markedly different from what has been reported so far in disordered insulators.
Like in the most studied systems (indium oxide and granular Al films), a slow
relaxation of the conductance is observed after a quench to liquid helium
temperature which gives rise to the growth of a memory dip in MOSFET devices.
But unlike in these systems, this memory dip and the related conductance
relaxations are still visible up to room temperature, with clear signatures of
a temperature dependent dynamics
Stimulate feed intake before weaning and control intake after weaning to optimise health and growth performance
[EN] Post-weaning feed restriction is a common practice in rabbit farming to reduce mortality, but results in lower growth performance and slaughter weights. This study aimed to assess the influence of 2 diets both rich in fibre and low in starch, with high or low digestible energy (DE) and digestible protein (DP) contents for a constant DP/DE ratio offered from 18 to 70 d of age, on the growth performance and health parameters of rabbits. Eight hundred rabbit kits were divided in 2 experimental groups differing in the feed offered from 18 to 70 d: a high concentrate diet (HC group; 10.37 MJ DE/kg DM and 102 g DP/kg DM) or low concentrate diet (LC group; 9.63 MJ DE/kg DM and 95 g DP/kg DM). Feed was offered ad libitum before weaning (35 d) and from 63 to 70 d, while feed offered from 35 to 63 d was controlled to obtain similar DE intake in both groups. Feed intake, animal weights and health status were recorded weekly. Mortality was recorded daily. Feed intake was similar in both groups before weaning (P=0.204), and consequently the DE intake was higher in the HC group compared to the LC group before weaning (3.91 vs. 3.39 MJ, respectively; P=0.017). Feed intake from 63 to 70 d was lower in the HC than in the LC group (229 vs. 239 g/d/kit, respectively; P<0.001).Total DE ingested after weaning was similar in both groups (45.44 MJ; P=0.143). Kits were heavier in the HC group throughout the study (P<0.05). A higher average daily gain during the periods of 18-28, 35-42 and 56-63 d was seen in the HC group (+8.1%, +16.8% and +4.5%, respectively; P<0.05). Mortality and morbidity rates were similar between groups throughout the study (P=1.0 and P=0.104, respectively). Our results suggest that when the feed intake after weaning is controlled, i) the feeding strategy before weaning determines the weight at weaning and at slaughter age; and ii) rabbits fed a diet more highly concentrated but rich in fibre increase their growth performance without negative consequences on their digestive health.The authors gratefully acknowledge the technical help of C. Bannelier, B. Gabinaud and M. Segura (INRA, UMR
1388 GenPhySE), and the assistance of the staff at the rabbit experimental unit (PECTOUL, Toulouse, France).Read, T.; Combes, S.; Gidenne, T.; Destombes, N.; Grenet, L.; Fortun-Lamothe, L. (2015). Stimulate feed intake before weaning and control intake after weaning to optimise health and growth performance. World Rabbit Science. 23(3):145-153. doi:10.4995/wrs.2015.3977SWORD14515323
Electronic and physico-chemical properties of nanmetric boron delta-doped diamond structures
Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called deltadoped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe
resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6K<T<450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.660.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm.14 page
GrAHal-CAPP for axion dark matter search with unprecedented sensitivity in the 1–3 μeV mass range
A collaboration between CNRS-Grenoble and IBS-CAPP Daejeon plans to build a Sikivie’s type haloscope for axion/ALPs dark matter search at the Dine-Fischler-Srednicki-Zhitnitskii sensitivity for the 300–600 MHz range. It will be based on the large-bore superconducting “outsert” coil of the Grenoble hybrid magnet, providing a central magnetic field up to 9 T in an 810-mm warm bore diameter. This magnet has recently been successfully powered up to 8.5 T, achieving the first step of the electrical commissioning phase. The design principles of the cryostat with its double dilution refrigerators to cool below 50 mK, the light Cu RF cavity of 700-mm diameter, and its tuning rod(s) and the first stages of the measurement chain are presented. Perspectives for the targeted sensitivity assuming less than a 2-year integration time are given
Etude d'effets de granularite dans les nouveaux supraconducteurs de la famille de Nd-Ce-Cu-O
SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 82237 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Slow conductance relaxation in granular aluminium films
the proceedings editor does not allow on-line preprints (!) link to the paper on the editor site: http://onlinelibrary.wiley.com/doi/10.1002/pssc.200303622/abstractInternational audienceConductance measurements of thin granular aluminium films are reported. They exhibit a symmetrical field effect anomaly and slow relaxation of the conductance after the samples are put out of equilibrium by abruptly changing the temperature or the gate voltage. The results are identical to the ones reported in InOx thin films, suggesting that these phenomena are quite general in disordered insulators. The study of granular systems may help to elucidate the origin of the glassy behaviour
Symmetric Determinantal Representations in Characteristic 2
3 figuresInternational audienceThis paper studies Symmetric Determinantal Representations (SDR) in characteristic 2, that is the representation of a multivariate polynomial P by a symmetric matrix M such that P=det(M), and where each entry of M is either a constant or a variable. We first give some sufficient conditions for a polynomial to have an SDR. We then give a non-trivial necessary condition, which implies that some polynomials have no SDR, answering a question of Grenet et al. A large part of the paper is then devoted to the case of multilinear polynomials. We prove that the existence of an SDR for a multilinear polynomial is equivalent to the existence of a factorization of the polynomial in certain quotient rings. We develop some algorithms to test the factorizability in these rings and use them to find SDRs when they exist. Altogether, this gives us polynomial-time algorithms to factorize the polynomials in the quotient rings and to build SDRs. We conclude by describing the case of Alternating Determinantal Representations in any characteristic