708 research outputs found
Uncooled bolometer response of a low noise La2/3Sr1/3MnO3 thin film
We report measurements of the optical responses of a La2/3Sr1/3MnO3 (LSMO)
sample at a wavelength of 533 nm in the 300-400 K range. The 200 nm thick film
was grown by pulsed laser deposition on (100) SrTiO3 substrate and showed
remarkably low noise. At 335 K the temperature coefficient of the resistance of
a 100 micrometers wide 300 micrometers long LSMO line was 0.017 K-1 and the
normalized Hooge parameter was 9 e-30 m3, which is among the lowest reported
values. We then measured an optical sensitivity at I = 5 mA of 10.4 V.W-1 and
corresponding noise equivalent power (NEP) values of 8.1 e-10 W.Hz-1/2 and 3.3
e-10 W. Hz-1/2 at 30 Hz and above 1kHz, respectively. Simple considerations on
bias current conditions and thermal conductance G are finally given for further
sensitivity improvements using LSMO films. The performances were indeed
demonstrated on bulk substrates with G of 10-3 W.K-1. One could expect a NEP
reduction by three orders of magnitude if a membrane-type geometry was used,
which makes this LSMO device competitive against commercially available
uncooled bolometers.Comment: 15 pages. Accepted for publication in Appl. Phys. Let
Propagation of social representations
Based on a minimal formalism of social representations as a set of associated cognems, a simple model of propagation of representations is presented. Assuming that subjects share the constitutive cognems, the model proposes that mere focused attention on the set of cognems in the field of common conscience may replicate the pattern of representation from context into subjects, or, from subject to subject, through actualization by language, where cognems are represented by verbal signs. Limits of the model are discussed, and evolutionist perspectives are presented with the support of field data
Modulated optical reflectance measurements on La2/3Sr1/3MnO3 thin films
The modulated optical reflectance (MOR) measurement technique was applied to
colossal magnetoresistive materials, in particular, La2/3Sr1/3MnO3 (LSMO) thin
films. The contactless measurement scheme is prospective for many applications
spanning from materials characterization to new devices like reading heads for
magnetically recorded media. A contrasted room temperature surface scan of a
100 microns wide 400 microns long bridge patterned into LSMO film provided
preliminary information about the film homogeneity. Then the temperature was
varied between 240 and 400 K, i.e. through the ferromagnetic to paramagnetic
transition. A clear relation between the MOR signal measured as function of the
temperature and the relative derivative of the resistivity up to the Curie
temperature was observed. This relationship is fundamental for the MOR
technique and its mechanism was explored in the particular case of LSMO.
Analysis in the framework of the Drude model showed that, within certain
conditions, the measured MOR signal changes are correlated to changes in the
charge carrier concentration.Comment: 29 pages, accepted for publication in J. Appl. Phy
Ridge subduction sparked reorganization of the Pacific plate-mantle system 60-50 million years ago
A reorganization centered on the Pacific plate occurred ~53–47 million years ago. A “top-down” plate tectonic mechanism, complete subduction of the Izanagi plate, as opposed to a “bottom-up” mantle flow mechanism, has been proposed as the main driver. Verification based on marine geophysical observations is impossible as most ocean crust recording this event has been subducted. Using a forward modeling approach, which assimilates surface plate velocities and shallow thermal structure of slabs into mantle flow models, we show that complete Izanagi plate subduction and margin-wide slab detachment induced a major change in sub-Pacific mantle flow, from dominantly southward before 60 Ma to north-northeastward after 50 Ma. Our results agree with onshore geology, mantle tomography, and the inferred motion of the Hawaiian hot spot and are consistent with a plate tectonic process driving the rapid plate-mantle reorganization in the Pacific hemisphere between 60 and 50 Ma. This reorganization is reflected in tectonic changes in the Pacific and surrounding ocean basins
Moored current meter, AVHRR, CTD, and drifter data from the Agulhas Current and Retroflexion region (1985-1987) Volume XLII
Stored in the Archives of the Woods Hole Oceanographic Institution is the floppy disk on which can be found the one-day average currents, the path of the Agulhas Current, CTD stations in "Live Atlas" format, SST frontal analyses (Chassignet and Olson, personal communcation) as well as
programs written in QuickBASIC which allow one to access and display these observations. The programs are stored in ASCII and
can be run under the Microsoft QuickBasic (Version 4.0 or higher). Instructions for running the programs can be found in a file
entitled "read.me" on the disk.Data are presented from an experiment designed to explore the spatial and temporal structure of the Agulhas Current and
Retroflexion by direct means. Included are the current meter results from 10 moorings in the Retroflexion region, CTD stations
occupied on the deployment cruise in 1985, data from satellite tracked (ARGOS) freely during surface buoys and numerous images
of the sea surface temperature.Funding was provided by the Office of Naval Research through Contract Nos.
NOOO14-84C-O134, NOO014-85-C-0001, and NOOO14-87-K-0007
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The Role of Electron Transport and Trapping in MOS Total-Dose Modeling
Deep and shallow electron traps form in irradiated thermal SiO{sub 2} as a natural response to hole transport and trapping. The density and stability of these defects are discussed, as are their implications for total-dose modeling
Integrated North Sea grids: The costs, the benefits and their distribution between countries
A large number of offshore wind farms and interconnectors are expected to be constructed in the North Sea region over the coming decades, creating substantial opportunities for the deployment of integrated network solutions. Creating interconnected offshore grids that combine cross-border links and connections of offshore plants to shore offers multiple economic and environmental advantages for Europe's energy system. However, despite evidence that integrated solutions can be more beneficial than traditional radial connection practices, no such projects have been deployed yet. In this paper we quantify costs and benefits of integrated projects and investigate to which extent the cost-benefit sharing mechanism between participating countries can impede or encourage the development of integrated projects. Three concrete interconnection case studies in the North Sea area are analysed in detail using a national-level power system model. Model outputs are used to compute the net benefit of all involved stakeholders under different allocation schemes. Given the asymmetric distribution of costs and benefits, we recommend to consistently apply the Positive Net Benefit Differential mechanism as a starting point for negotiations on the financial closure of investments in integrated offshore infrastructure
The Shapes of Flux Domains in the Intermediate State of Type-I Superconductors
In the intermediate state of a thin type-I superconductor magnetic flux
penetrates in a disordered set of highly branched and fingered macroscopic
domains. To understand these shapes, we study in detail a recently proposed
"current-loop" (CL) model that models the intermediate state as a collection of
tense current ribbons flowing along the superconducting-normal interfaces and
subject to the constraint of global flux conservation. The validity of this
model is tested through a detailed reanalysis of Landau's original conformal
mapping treatment of the laminar state, in which the superconductor-normal
interfaces are flared within the slab, and of a closely-related straight-lamina
model. A simplified dynamical model is described that elucidates the nature of
possible shape instabilities of flux stripes and stripe arrays, and numerical
studies of the highly nonlinear regime of those instabilities demonstrate
patterns like those seen experimentally. Of particular interest is the buckling
instability commonly seen in the intermediate state. The free-boundary approach
further allows for a calculation of the elastic properties of the laminar
state, which closely resembles that of smectic liquid crystals. We suggest
several new experiments to explore of flux domain shape instabilities,
including an Eckhaus instability induced by changing the out-of-plane magnetic
field, and an analog of the Helfrich-Hurault instability of smectics induced by
an in-plane field.Comment: 23 pages, 22 bitmapped postscript figures, RevTex 3.0, submitted to
Phys. Rev. B. Higher resolution figures may be obtained by contacting the
author
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