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Search Results: 1 - 10 of 26337 matches for " Jean Schmidt "
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O método transiente eletromagnético (tem) aplicado ao imageamento geoelétrico da bacia de resende (RJ, Brasil)
Santos, Hans Schmidt;Flexor, Jean Marie;
Revista Brasileira de Geofísica , 2008, DOI: 10.1590/S0102-261X2008000400013
Abstract: this work presents an application of the transient electromagnetic geophysical method in the area of basin of resende, rio de janeiro, brazil. ln this basin, it was made in 2001, a geophysical survey of 88 soundings seeking to contribute for the knowledge of the hydrogeological potential of the area. this area is densely industrialized, so noise tends to hinder the use of the method. the data were interpreted using an 1-d inversion algorithm where the resistivity in depth is estimated from the induced voltage time decay. surface shows highly conductive layers (~5ω.m) and the value of 200ω.m for the transition resistivity coresponding to the geoelectric basement was suggested from lithology and stratigraphy data of the basin together with a fine adjustment gauged in the 3-d gravity model of the basin. from the 1-d inversion we built up a pseudo-3d geoelectric image of the basement geometry. despite the physical properties involved (density and resistivity) does not have any relationship between them, the topography of a previous gravity basement was used to estimate depths that were not reached by the tem signal. the resulting surface has a topography which is assumed be representative of the basin's basement. so, the use the tem method in basin of resende allowed to estimate the lateral limits of the basin and to propose limits in depth. three areas can be depicted: a structural high flanked by two structural lows (depocenters), one to east and the other to west of the basin.
On submanifolds in locally symmetric spaces of noncompact type
Jean-Francois Lafont,Benjamin Schmidt
Mathematics , 2006, DOI: 10.2140/agt.2006.6.2455
Abstract: Given a connected, compact, totally geodesic submanifold Y^m of noncompact type inside a compact locally symmetric space of noncompact type X^n, we provide a sufficient condition that ensures that [Y^m] is nonzero in H_m(X^n; R); in low dimensions, our condition is also necessary. We provide conditions under which there exist a tangential map of pairs from a finite cover (X-bar,Y-bar) to the nonnegatively curved duals (X_u,Y_u).
Signal Processing with High Complexity: Prototyping and Industrial Design
Markus Rupp,Thomas Kaiser,Jean-Francois Nezan,Gerhard Schmidt
EURASIP Journal on Embedded Systems , 2006, DOI: 10.1155/es/2006/90363
Signal Processing with High Complexity: Prototyping and Industrial Design
Rupp Markus,Kaiser Thomas,Nezan Jean-Francois,Schmidt Gerhard
EURASIP Journal on Embedded Systems , 2006,
Rigidity of Almost-Isometric Universal Covers
Aditi Kar,Jean-Francois Lafont,Benjamin Schmidt
Mathematics , 2014,
Abstract: Almost-isometries are quasi-isometries with multiplicative constant one. Lifting a pair of metrics on a compact space gives quasi-isometric metrics on the universal cover. Under some additional hypotheses on the metrics, we show that there is no almost-isometry between the universal covers. We show that Riemannian manifolds which are almost-isometric have the same volume growth entropy. We establish various rigidity results as applications.
Quasicircle boundaries and exotic almost-isometries
Jean-Francois Lafont,Benjamin Schmidt,Wouter van Limbeek
Mathematics , 2014,
Abstract: We consider properly discontinuous, isometric, convex cocompact actions of surface groups on a CAT(-1) space. We show that the limit set of such an action, equipped with the canonical visual metric, is a (weak) quasicircle in the sense of Falconer and Marsh. It follows that the visual metrics on such limit sets are classified, up to bi-Lipschitz equivalence, by their Hausdorff dimension. This result applies in particular to boundaries at infinity of the universal cover of a locally CAT(-1) surface. We show that any two periodic CAT(-1) metrics on $\mathbb H^2$ can be scaled so as to be almost-isometric (though in general, no equivariant almost-isometry exists). We also construct, on each higher genus surface, $k$-dimensional families of equal area Riemannian metrics, with the property that their lifts to the universal covers are pairwise almost-isometric but are not isometric to each other. Finally, we exhibit a gap phenomenon for the optimal multiplicative constant for a quasi-isometry between periodic CAT(-1) metrics on $\mathbb H^2$.
Dependence of Gravity Induced Absorption Changes on the Earth’s Magnetic Field as Measured during Parabolic Flight Campaigns  [PDF]
Werner Schmidt
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.411190

Various spectroscopic experiments performed on the AIRBUS ZERO G—located in Bordeaux, France—in the years 2002 to 2012 exhibit minute optical reflection/absorption changes (GIACs) as a result of gravitational changes between 0 and 1.8 g in various biological species such as maize, oats, Arabidopsis and particularly Phycomyces sporangiophores. During a flight day, the AIRBUS ZERO G conducts 31 parabolas, each of which lasts about three minutes including a period of 22 s of weightlessness. So far, we participated in 11 parabolic flight campaigns including more than 1000 parabolas performing various kinds of experiments. During our campaigns, we observed an unexplainable variability of the measuring signals (GIACs). Using GPS-positioning systems and three dimensional magnetic field sensors, these finally were traced back to the changing earth’s magnetic field associated with the various flight directions. This is the first time that the interaction of

Gravireception in Phycomyces: Threshold Determination on the Sounding Rocket TEXUS 50  [PDF]
Werner Schmidt
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.610143
Abstract: Under parabolic flight conditions microgravity is not lower than 3 to 5 times 10-2 g. In contrast to parabolic flights, sounding rocket flights are virtually vibrational-free allowing microgravity as low as 10-5 g. Thus, a rotating platform serving as centrifuge allows the precise generation of gravitational forces ranging from 5 to 100 mg (not possible during parabolic flights). On this basis we determined the threshold1 for optical reflection/absorption changes in Phycomyces to be lower than 25 × 10-3 g. This compares well with the threshold determination of gravitropism in Phycomyces on a clinostat centrifuge. Kinetics of gravity-induced absorption changes and gravity as generated by the on-board centrifuge do not coincide but show a distinctive hysteresis with a latency of 4 s (75 mg-ramp, pull-up).
Hyper Gravity-Induced Transients in Phycomyces as Measured by Single Beam Spectrophotometer on the Sounding Rocket TEXUS 50  [PDF]
Werner Schmidt
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.92019
Abstract: In the first paper of two referring to the TEXUS 50 campaign using micro dual wavelength spectrometers (MDWS) we kinetically determined the threshold1 for GIACs (gravity-induced absorption changes) in Phycomyces to be lower than 25 × 103 g (http://file.scirp.org/pdf/JMP_2015082810060783.pdf). In this second paper, we attended measurement of GIAC-spectra. Unexpectedly, during the upwards movement, i.e. the hypergravity phase up to top acceleration values reaching 11.6 g at 35.4 s after liftoff we observed transient GIAC-spectra ranging from 380 to 750 nm. In addition, during the whole acceleration phase of 68.2 s, another component near 700 nm develops which remains stable during the whole “free fall trajectory parabola” for 381.3 s. The subsequent reentry of the rocket leads to extraordinary deceleration values up 37.8 g, completely destroying Phycomyces sporangiophores excluding their spectral measurement. During the microgravity phase and by centrifuge operation we were unable to detect any GIAC-spectra (in contrast to kinetic MDWS-measurements, first paper).
Neural Mechanisms Underlying Motivation of Mental Versus Physical Effort
Liane Schmidt,Ma?l Lebreton,Marie-Laure Cléry-Melin,Jean Daunizeau,Mathias Pessiglione
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001266
Abstract: Mental and physical efforts, such as paying attention and lifting weights, have been shown to involve different brain systems. These cognitive and motor systems, respectively, include cortical networks (prefronto-parietal and precentral regions) as well as subregions of the dorsal basal ganglia (caudate and putamen). Both systems appeared sensitive to incentive motivation: their activity increases when we work for higher rewards. Another brain system, including the ventral prefrontal cortex and the ventral basal ganglia, has been implicated in encoding expected rewards. How this motivational system drives the cognitive and motor systems remains poorly understood. More specifically, it is unclear whether cognitive and motor systems can be driven by a common motivational center or if they are driven by distinct, dedicated motivational modules. To address this issue, we used functional MRI to scan healthy participants while performing a task in which incentive motivation, cognitive, and motor demands were varied independently. We reasoned that a common motivational node should (1) represent the reward expected from effort exertion, (2) correlate with the performance attained, and (3) switch effective connectivity between cognitive and motor regions depending on task demand. The ventral striatum fulfilled all three criteria and therefore qualified as a common motivational node capable of driving both cognitive and motor regions of the dorsal striatum. Thus, we suggest that the interaction between a common motivational system and the different task-specific systems underpinning behavioral performance might occur within the basal ganglia.
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