828 research outputs found
Important Parameters for Hand Function Assessment of Stroke Patients
Clinical scales such as Fugl-Meyer Assessment and Motor Assessment Scale are widely used to evaluate stroke patient's motor performance. However, the scoring systems of these assessments provide only rough estimation, making it difficult to objectively quantify impairment and disability or even rehabilitation progress throughout their rehabilitation period. In contrast, robot-based assessments are objective, repeatable, and could potentially reduce the assessment time. However, robot-based assessment scales are not as well established as conventional assessment scale and the correlation to conventional assessment scale is unclear. This paper discusses the important parameters in order to assess the hand function of stroke patients. This knowledge will provide a contribution to the development of a new robot-based assessment device effectively by including the important parameters in the device. The important parameters were included in development of iRest and yielded promising results that illustrate the potential of the important parameters in assessing the hand function of stroke patients
Automatic Alignment of pre and intraoperative Data using Anatomical Landmarks for Augmented Laparoscopic Liver Surgery
International audienceEach year in Europe 50,000 new liver cancer cases are diagnosed for which hepatic surgery combined to chemotherapy is the most common treatment. In particular the number of laparoscopic liver surgeries has increased significantly over the past years. This type of minimally invasive procedure which presents many benefits for the patient is challenging for the surgeons due to the limited field of view. Recently new augmented reality techniques which merge preoperative data and intraoperative images and permit to visualize internal structures have been proposed to help surgeons during this type of surgery. One of the difficulties is to align preoperative data with the intraoperative images. We propose in this paper a semi-automatic approach for solving the ill-posed problem of initial alignment for Augmented Reality systems during liver surgery. Our registration method relies on anatomical landmarks extracted from both the laparoscopic images and three-dimensional model, using an image-based soft-tissue reconstruction technique and an atlas-based approach, respectively. The registration evolves automatically from a quasi-rigid to a non-rigid registration. Furthermore, the surface-driven deformation is induced in the volume via a patient specific biomechanical model. The experiments conducted on both synthetic and in vivo data show promising results with a registration error of 2 mm when dealing with a visible surface of 30% of the whole liver
On Signatures of Twisted Magnetic Flux Tube Emergence
Recent studies of NOAA active region 10953, by Okamoto {\it et al.} ({\it
Astrophys. J. Lett.} {\bf 673}, 215, 2008; {\it Astrophys. J.} {\bf 697}, 913,
2009), have interpreted photospheric observations of changing widths of the
polarities and reversal of the horizontal magnetic field component as
signatures of the emergence of a twisted flux tube within the active region and
along its internal polarity inversion line (PIL). A filament is observed along
the PIL and the active region is assumed to have an arcade structure. To
investigate this scenario, MacTaggart and Hood ({\it Astrophys. J. Lett.} {\bf
716}, 219, 2010) constructed a dynamic flux emergence model of a twisted
cylinder emerging into an overlying arcade. The photospheric signatures
observed by Okamoto {\it et al.} (2008, 2009) are present in the model although
their underlying physical mechanisms differ. The model also produces two
additional signatures that can be verified by the observations. The first is an
increase in the unsigned magnetic flux in the photosphere at either side of the
PIL. The second is the behaviour of characteristic photospheric flow profiles
associated with twisted flux tube emergence. We look for these two signatures
in AR 10953 and find negative results for the emergence of a twisted flux tube
along the PIL. Instead, we interpret the photospheric behaviour along the PIL
to be indicative of photospheric magnetic cancellation driven by flows from the
dominant sunspot. Although we argue against flux emergence within this
particular region, the work demonstrates the important relationship between
theory and observations for the successful discovery and interpretation of
signatures of flux emergence.Comment: 14 pages, 8 figures, accepted for publication in Solar Physic
Polaron formation for a non-local electron-phonon coupling: A variational wave-function study
We introduce a variational wave-function to study the polaron formation when
the electronic transfer integral depends on the relative displacement between
nearest-neighbor sites giving rise to a non-local electron-phonon coupling with
optical phonon modes. We analyze the ground state properties such as the
energy, the electron-lattice correlation function, the phonon number and the
spectral weight. Variational results are found in good agreement with analytic
weak-coupling perturbative calculations and exact numerical diagonalization of
small clusters. We determine the polaronic phase diagram and we find that the
tendency towards strong localization is hindered from the pathological sign
change of the effective next-nearest-neighbor hopping.Comment: 11 page
Generalized hole-particle transformations and spin reflection positivity in multi-orbital systems
We propose a scheme combining spin reflection positivity and generalized
hole-particle and orbital transformations to characterize the symmetry
properties of the ground state for some correlated electron models on bipartite
lattices. In particular, we rigorously determine at half-filling and for
different regions of the parameter space the spin, orbital and pairing
pseudospin of the ground state of generalized two-orbital Hubbard models which
include the Hund's rule coupling.Comment: 6 pages, 2 figure
A Parametric Study of Erupting Flux Rope Rotation. Modeling the "Cartwheel CME" on 9 April 2008
The rotation of erupting filaments in the solar corona is addressed through a
parametric simulation study of unstable, rotating flux ropes in bipolar
force-free initial equilibrium. The Lorentz force due to the external shear
field component and the relaxation of tension in the twisted field are the
major contributors to the rotation in this model, while reconnection with the
ambient field is of minor importance. Both major mechanisms writhe the flux
rope axis, converting part of the initial twist helicity, and produce rotation
profiles which, to a large part, are very similar in a range of shear-twist
combinations. A difference lies in the tendency of twist-driven rotation to
saturate at lower heights than shear-driven rotation. For parameters
characteristic of the source regions of erupting filaments and coronal mass
ejections, the shear field is found to be the dominant origin of rotations in
the corona and to be required if the rotation reaches angles of order 90
degrees and higher; it dominates even if the twist exceeds the threshold of the
helical kink instability. The contributions by shear and twist to the total
rotation can be disentangled in the analysis of observations if the rotation
and rise profiles are simultaneously compared with model calculations. The
resulting twist estimate allows one to judge whether the helical kink
instability occurred. This is demonstrated for the erupting prominence in the
"Cartwheel CME" on 9 April 2008, which has shown a rotation of \approx 115
degrees up to a height of 1.5 R_sun above the photosphere. Out of a range of
initial equilibria which include strongly kink-unstable (twist Phi=5pi), weakly
kink-unstable (Phi=3.5pi), and kink-stable (Phi=2.5pi) configurations, only the
evolution of the weakly kink-unstable flux rope matches the observations in
their entirety.Comment: Solar Physics, submitte
Serine-385 phosphorylation of inwardly rectifying K(+) channel subunit (Kir6.2) by AMP-dependent protein kinase plays a key role in rosiglitazone-induced closure of the K(ATP) channel and insulin secretion in rats
Rosiglitazone, an insulin sensitiser, not only improves insulin sensitivity but also enhances insulin secretory capacity by ameliorating gluco- and lipotoxicity in beta cells. Rosiglitazone can stimulate insulin secretion at basal and high glucose levels via a phosphatidylinositol 3-kinase (PI3K)-dependent pathway. We hypothesised that regulation of phosphorylation of the ATP-sensitive potassium (K(ATP)) channel might serve as a key step in the regulation of insulin secretion. Insulin secretory responses were studied in an isolated pancreas perfusion system, cultured rat islets and MIN6 and RINm5F beta cells. Signal transduction pathways downstream of PI3K were explored to link rosiglitazone to K(ATP) channel conductance with patch clamp techniques and insulin secretion measured by ELISA. Rosiglitazone stimulated AMP-activated protein kinase (AMPK) activity and induced inhibition of the K(ATP) channel conductance in islet beta cells; both effects were blocked by the PI3K inhibitor LY294002. Following stimulation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a pharmacological activator, both AICAR-stimulated insulin secretion and inhibition of K(ATP) channel conductance were unaffected by LY294002, indicating that AMPK activation occurs at a site downstream of PI3K activity. The serine residue at amino acid position 385 of Kir6.2 was found to be the substrate phosphorylation site of AMPK when activated by rosiglitazone or AICAR. Our data indicate that PI3K-dependent activation of AMPK is required for rosiglitazone-stimulated insulin secretion in pancreatic beta cells. Phosphorylation of the Ser(385) residue of the Kir6.2 subunit of the K(ATP) channel by AMPK may play a role in insulin secretion
D-concurrence bounds for pair coherent states
The pair coherent state is a state of a two-mode radiation field which is
known as a state with non-Gaussian wave function. In this paper, the upper and
lower bounds for D-concurrence (a new entanglement measure) have been studied
over this state and calculated.Comment: 11 page
Gravitomagnetic Effects in the Propagation of Electromagnetic Waves in Variable Gravitational Fields of Arbitrary-Moving and Spinning Bodies
Propagation of light in the gravitational field of self-gravitating spinning
bodies moving with arbitrary velocities is discussed. The gravitational field
is assumed to be "weak" everywhere. Equations of motion of a light ray are
solved in the first post-Minkowskian approximation that is linear with respect
to the universal gravitational constant . We do not restrict ourselves with
the approximation of gravitational lens so that the solution of light geodesics
is applicable for arbitrary locations of source of light and observer. This
formalism is applied for studying corrections to the Shapiro time delay in
binary pulsars caused by the rotation of pulsar and its companion. We also
derive the correction to the light deflection angle caused by rotation of
gravitating bodies in the solar system (Sun, planets) or a gravitational lens.
The gravitational shift of frequency due to the combined translational and
rotational motions of light-ray-deflecting bodies is analyzed as well. We give
a general derivation of the formula describing the relativistic rotation of the
plane of polarization of electromagnetic waves (Skrotskii effect). This formula
is valid for arbitrary translational and rotational motion of gravitating
bodies and greatly extends the results of previous researchers. Finally, we
discuss the Skrotskii effect for gravitational waves emitted by localized
sources such as a binary system. The theoretical results of this paper can be
applied for studying various relativistic effects in microarcsecond space
astrometry and developing corresponding algorithms for data processing in space
astrometric missions such as FAME, SIM, and GAIA.Comment: 36 pages, 1 figure, submitted to Phys. Rev.
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