Knee dislocation in overweight patients

Peer reviewe

Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary

Functional Magnetic Resonance Imaging Blood Oxygenation Level-Dependent Signal and Magnetoencephalography Evoked Responses Yield Different Neural Functionality in Reading

It is often implicitly assumed that the neural activation patterns revealed by hemodynamic methods, such as functional magnetic resonance imaging (fMRI), and electrophysiological methods, such as magnetoencephalography (MEG) and electroencephalography (EEG), are comparable. In early sensory processing that seems to be the case, but the assumption may not be correct in high-level cognitive tasks. For example, MEG and fMRI literature of single-word reading suggests differences in cortical activation, but direct comparisons are lacking. Here, while the same human participants performed the same reading task, analysis of MEG evoked responses and fMRI blood oxygenation level-dependent (BOLD) signals revealed marked functional and spatial differences in several cortical areas outside the visual cortex. Divergent patterns of activation were observed in the frontal and temporal cortex, in accordance with previous separate MEG and fMRI studies of reading. Furthermore, opposite stimulus effects in the MEG and fMRI measures were detected in the left occipitotemporal cortex: MEG evoked responses were stronger to letter than symbol strings, whereas the fMRI BOLD signal was stronger to symbol than letter strings. The EEG recorded simultaneously during MEG and fMRI did not indicate neurophysiological differences that could explain the observed functional discrepancies between the MEG and fMRI results. Acknowledgment of the complementary nature of hemodynamic and electrophysiological measures, as reported here in a cognitive task using evoked response analysis in MEG and BOLD signal analysis in fMRI, represents an essential step toward an informed use of multimodal imaging that reaches beyond mere combination of location and timing of neural activationPeer reviewe

Universal vortex formation in rotating traps with bosons and fermions

When a system consisting of many interacting particles is set rotating, it may form vortices. This is familiar to us from every-day life: you can observe vortices while stirring your coffee or watching a hurricane. In the world of quantum mechanics, famous examples of vortices are superconducting films and rotating bosonic $^4$He or fermionic $^3$He liquids. Vortices are also observed in rotating Bose-Einstein condensates in atomic traps and are predicted to exist for paired fermionic atoms. Here we show that the rotation of trapped particles with a repulsive interaction leads to a similar vortex formation, regardless of whether the particles are bosons or (unpaired) fermions. The exact, quantum mechanical many-particle wave function provides evidence that in fact, the mechanism of this vortex formation is the same for boson and fermion systems.Comment: 4 pages, 4 figure

Kannettavan XRD:n mahdollisuudet malminetsinnässä

Tiivistelmä. Röntgendiffraktiomenetelmä on keksitty jo 1900-luvun alussa ja sitä on käytetty mineraalien tutkimuksessa siitä lähtien. Kannettavia XRD-laitteita ei kuitenkaan ole vielä ollut laajassa käytössä muutamia kokeiluja lukuun ottamatta. Kannettava XRF (röntgenfluoresenssianalysaattori) sen sijaan on jo vakiinnuttanut paikkansa esimerkiksi malminetsinnässä kenttänäytteenottoa kohdentavana menetelmänä. Sillä saadaan analysoitua näytteen kemiallinen koostumus, mutta ei näytteen sisältämiä mineraaleja kuten XRD:llä. Kannettavaan XRF-analysaattoriin verrattuna kannettavalla XRD- laitteella on enemmän geometrisiä vaatimuksia, minkä takia sen kehittäminen on ollut hankalampaa. Markkinoille on kuitenkin saatu XRF- ja XRD-tekniikat yhdistäviä kannettavia laitteita. Kummallakin menetelmällä on rajoitteensa, mutta yhdessä käytettynä ne täydentävät toisiaan. Tässä työssä tarkastellaan kannettavan XRD:n toimintaperiaatteita sekä kokemuksia yhdistetyn XRD/XRF-laitteen käytöstä kentällä. Tarkoituksena on myös aiempien kenttätutkimusten perusteella selvittää menetelmän mahdollisuuksia ja rajoitteita kriittisten mineraalien ja niiden indikaattorimineraalien etsinnässä. Laitteen käyttökelpoisuus riippuu muun muassa sen tuottaman tiedon tarkkuudesta ja luotettavuudesta verrattuna muihin, lähinnä laboratorio-olosuhteissa käytettäviin menetelmiin. Tärkeitä kriteerejä ovat myös menetelmän nopeus sekä se, millaisille näytteille menetelmä sopii ja paljonko esikäsittelyä näytteille pitää tehdä

Escaping Particle fluxes in the atmospheres of close-in exoplanets: I. model of hydrogen

A multi-fluid model for an atomic hydrogen-proton mixture in the upper atmosphere of extrosolar planet is presented when the continuity and momentum equations of each component have been already solved with an energy equation. The particle number density, the temperature distribution and the structure of velocity can be found by means of the model. We chose two special objects, HD 209458b and HD 189733b, as discussion samples and the conclusion is that their mass loss rates predicted by the model are in accordance with those of observation. The most important physical process in coupling each component is charge exchange which tightly couples atomic hydrogen with protons. Most of the hydrogen escaping from hot Jupiters is protons, especially in young star-planet system. We found that the single-fluid model can describe the escape of particles when the mass loss rate is higher than a few times $10^{9}$ g/s while below $10^{9}$ g/s the multi-fluid model is more suitable for it due to the decoupling of particles. We found that the predicted mass loss rates of HD 189733b with the assumption of energy-limit are a factor of 10 larger than that calculated by our models due to the high ionization degree. For the ionized wind which is almost compose of protons, the assumption of energy-limit is no longer effective. We fitted the mass loss rates of the ionized wind as a function of $F_{UV}$ by calculating the variation of the mass loss rates with UV fluxes.Comment: 35 pages, 6 figures, submitted to Ap