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1.
The second-sound velocity of a superfluid mixture increases when a static and homogeneous magnetic field is applied. In particular, for dilute mixtures (molar
3
He concentration <0.1) and low temperatures, (0.1<T<0.6 K) the relative velocity increase is independent of concentration and is given by u
2/u
25×10–16
B
e
2
T
–2. It should be easily observed wheneverB
e
T
–1is larger than 10
5
G K–1
and can lead to a novel measurement of the magnetic susceptibility. 相似文献
2.
We study how the Néel order breaks the symmetries of the hamiltonian in quantum antiferromagnet. The construction of a quantum wave packet that mimics the classical groundstate implies the existence of an extensive number of states: 1) with an energy scale much smaller than the spin-waves excitations (magnons); 2) with well defined symmetries.For the case of the triangular lattice, we find that all necessary properties to obtain a Néel state are well verified, already on periodic samples as small as 21 spins. For this system, this is a new and strong evidence of Néel order in the thermodynamic limit. 相似文献
3.
Eric Royer Maxime Lhuillier Michel Dhome Jean-Marc Lavest 《International Journal of Computer Vision》2007,74(3):237-260
This paper presents a new real-time localization system for a mobile robot. We show that autonomous navigation is possible
in outdoor situation with the use of a single camera and natural landmarks. To do that, we use a three step approach. In a
learning step, the robot is manually guided on a path and a video sequence is recorded with a front looking camera. Then a
structure from motion algorithm is used to build a 3D map from this learning sequence. Finally in the navigation step, the
robot uses this map to compute its localization in real-time and it follows the learning path or a slightly different path
if desired. The vision algorithms used for map building and localization are first detailed. Then a large part of the paper
is dedicated to the experimental evaluation of the accuracy and robustness of our algorithms based on experimental data collected
during two years in various environments. 相似文献
4.
5.
The functional expression of Ca2+-activated K+ channels (KCa) in developing chick ciliary ganglion (CG) neurons requires interactions with target tissues and preganglionic innervation. Here, we show that the stimulatory effects of target tissues are mediated by an isoform of TGFbeta. Exposure of cultured CG neurons to TGFbeta1, but not TGFbeta2 or TGFbeta3, caused robust stimulation of KCa. The KCa stimulatory effects of target tissue extracts were blocked by a neutralizing pan-TGFbeta antiserum but not by specific TGFbeta2 or TGFbeta3 antisera. Intraocular injection of TGFbeta1 caused robust stimulation of KCa, whereas intraocular injection of pan-TGFbeta antiserum inhibited expression of KCa in CG neurons developing in vivo. The effects of TGFbeta1 were potentiated by beta-neuregulin-1, a differentiation factor expressed in preganglionic neurons. 相似文献
6.
7.
The majority of methods for the automatic surface reconstruction of an environment from an image sequence have two steps: Structure-from-Motion and dense stereo. From the computational standpoint, it would be interesting to avoid dense stereo and to generate a surface directly from the sparse cloud of 3D points and their visibility information provided by Structure-from-Motion. The previous attempts to solve this problem are currently very limited: the surface is non-manifold or has zero genus, the experiments are done on small scenes or objects using a few dozens of images. Our solution does not have these limitations. Furthermore, we experiment with hand-held or helmet-held catadioptric cameras moving in a city and generate 3D models such that the camera trajectory can be longer than one kilometer. 相似文献
8.
9.
We present the classical phase diagram of a multiple-spin exchange hamiltonian involving up to five-particle exchange. Schwinger-boson (mean field theory) calculations confirm the classical picture of competing ferromagnetic and antiferromagnetic phases, and suggest that the frustration induced by four-particle exchange might destroy long range order. 相似文献
10.