2,607 research outputs found
Grid simulation services for the medical community
The first part of this paper presents a selection of medical simulation applications, including image reconstruction, near real-time registration for neuro-surgery, enhanced dose distribution calculation for radio-therapy, inhaled drug delivery prediction, plastic surgery planning and cardio-vascular system simulation. The latter two topics are discussed in some detail. In the second part, we show how such services can be made available to the clinical practitioner using Grid technology. We discuss the developments and experience made during the EU project GEMSS, which provides reliable, efficient, secure and lawful medical Grid services
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Simulations of preindustrial, present-day, and 2100 conditions in the NASA GISS composition and climate model G-PUCCINI
International audienceA model of atmospheric composition and climate has been developed at the NASA Goddard Institute for Space Studies (GISS) that includes composition seamlessly from the surface to the lower mesosphere. The model is able to capture many features of the observed magnitude, distribution, and seasonal cycle of trace species. The simulation is especially realistic in the troposphere. In the stratosphere, high latitude regions show substantial biases during period when transport governs the distribution as meridional mixing is too rapid in this model version. In other regions, including the extrapolar tropopause region that dominates radiative forcing (RF) by ozone, stratospheric gases are generally well-simulated. The model's stratosphere-troposphere exchange (STE) agrees well with values inferred from observations for both the global mean flux and the ratio of Northern (NH) to Southern Hemisphere (SH) downward fluxes. Simulations of preindustrial (PI) to present-day (PD) changes show tropospheric ozone burden increases of 11% while the stratospheric burden decreases by 18%. The resulting tropopause RF values are ?0.06 W/m2 from stratospheric ozone and 0.40 W/m2 from tropospheric ozone. Global mean mass-weighted OH decreases by 16% from the PI to the PD. STE of ozone also decreased substantially during this time, by 14%. Comparison of the PD with a simulation using 1979 pre-ozone hole conditions for the stratosphere shows a much larger downward flux of ozone into the troposphere in 1979, resulting in a substantially greater tropospheric ozone burden than that seen in the PD run. This implies that reduced STE due to stratospheric ozone depletion may have offset as much as 2/3 of the tropospheric ozone burden increase from PI to PD. However, the model overestimates the downward flux of ozone at high Southern latitudes, so this estimate is likely an upper limit. In the future, the tropospheric ozone burden increases by 101% in 2100 for the A2 scenario including both emissions and climate changes. The primary reason is enhanced STE, which increases by 124% (168% in the SH extratropics, and 114% in the NH extratropics). Climate plays a minimal role in the SH increases, but contributes 38% in the NH. Chemistry and dry deposition both change so as to reduce tropospheric ozone, partially in compensation for the enhanced STE, but the increased ozone influx dominates the burden changes. The net RF due to projected ozone changes is 0.8 W/m2 for A2. The influence of climate change alone is ?0.2 W/m2, making it a substantial contributor to the net RF. The tropospheric oxidation capacity increases seven percent in the full A2 simulation, and 36% due to A2 climate change alone
Outskirts of Distant Galaxies In Absorption
QSO absorption spectroscopy provides a sensitive probe of both the neutral
medium and diffuse ionized gas in the distant Universe. It extends 21cm maps of
gaseous structures around low-redshift galaxies both to lower gas column
densities and to higher redshifts. Combining galaxy surveys with
absorption-line observations of gas around galaxies enables comprehensive
studies of baryon cycles in galaxy outskirts over cosmic time. This Chapter
presents a review of the empirical understanding of the cosmic neutral gas
reservoir from studies of damped Lya absorbers (DLAs). It describes the
constraints on the star formation relation and chemical enrichment history in
the outskirts of distant galaxies from DLA studies. A brief discussion of
available constraints on the ionized circumgalactic gas from studies of lower
column density Lya absorbers and associated ionic absorption transitions is
presented at the end.Comment: 45 pages, 7 figures, invited review, Book chapter in "Outskirts of
Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and
Space Science Library, Springer, in pres
Hydrogen-Helium Mixtures at High Pressure
The properties of hydrogen-helium mixtures at high pressure are crucial to
address important questions about the interior of Giant planets e.g. whether
Jupiter has a rocky core and did it emerge via core accretion? Using path
integral Monte Carlo simulations, we study the properties of these mixtures as
a function of temperature, density and composition. The equation of state is
calculated and compared to chemical models. We probe the accuracy of the ideal
mixing approximation commonly used in such models. Finally, we discuss the
structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum
Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004
A device for feasible fidelity, purity, Hilbert-Schmidt distance and entanglement witness measurements
A generic model of measurement device which is able to directly measure
commonly used quantum-state characteristics such as fidelity, overlap, purity
and Hilbert-Schmidt distance for two general uncorrelated mixed states is
proposed. In addition, for two correlated mixed states, the measurement
realizes an entanglement witness for Werner's separability criterion. To
determine these observables, the estimation only one parameter - the visibility
of interference, is needed. The implementations in cavity QED, trapped ion and
electromagnetically induced transparency experiments are discussed.Comment: 6 pages, 3 figure
Parametrization of projector-based witnesses for bipartite systems
Entanglement witnesses are nonpositive Hermitian operators which can detect
the presence of entanglement. In this paper, we provide a general
parametrization for orthonormal basis of and use it to
construct projector-based witness operators for entanglement detection in the
vicinity of pure bipartite states. Our method to parameterize entanglement
witnesses is operationally simple and could be used for doing symbolic and
numerical calculations. As an example we use the method for detecting
entanglement between an atom and the single mode of quantized field, described
by the Jaynes-Cummings model. We also compare the detection of witnesses with
the negativity of the state, and show that in the vicinity of pure stats such
constructed witnesses able to detect entanglement of the state.Comment: 12 pages, four figure
A trapped-ion local field probe
We introduce a measurement scheme that utilizes a single ion as a local field
probe. The ion is confined in a segmented Paul trap and shuttled around to
reach different probing sites. By the use of a single atom probe, it becomes
possible characterizing fields with spatial resolution of a few nm within an
extensive region of millimeters. We demonstrate the scheme by accurately
investigating the electric fields providing the confinement for the ion. For
this we present all theoretical and practical methods necessary to generate
these potentials. We find sub-percent agreement between measured and calculated
electric field values
The integrin expression profile modulates orientation and dynamics of force transmission at cellāmatrix adhesions
Integrin adhesion receptors connect the extracellular matrix (ECM) to the cytoskeleton and serve as bidirectional mechanotransducers. During development, angiogenesis, wound healing and cancer progression, the relative abundance of fibronectin receptors, including integrins Ī±5Ī²1 and Ī±vĪ²3, changes, thus altering the integrin composition of cell-matrix adhesions. Here, we show that enhanced Ī±vĪ²3 expression can fully compensate for loss of Ī±5Ī²1 and other Ī²1 integrins to support outside-in and inside-out force transmission. Ī±5Ī²1 and Ī±vĪ²3 each mediate actin cytoskeletal remodeling in response to stiffening or cyclic stretching of the ECM. Likewise, Ī±5Ī²1 and Ī±vĪ²3 support cellular traction forces of comparable magnitudes and similarly increase these forces in response to ECM stiffening. However, cells using Ī±vĪ²3 respond to lower stiffness ranges, reorganize their actin cytoskeleton more substantially in response to stretch, and show more randomly oriented traction forces. Centripetal traction force orientation requires long stress fibers that are formed through the action of Rho kinase (ROCK) and myosin II, and that are supported by Ī±5Ī²1. Thus, altering the relative abundance of fibronectin-binding integrins in cell-matrix adhesions affects the spatiotemporal organization of force transmission.Toxicolog
Physiological Responses Underlying the Perception of Effort during Moderate and Heavy Intensity Cycle Ergometry
This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 Ā± 0.5 years; 43.4 Ā± 2.0 mLĀ·kgā1Ā·minā1 VO2Peak) moderately trained cyclists performed an incremental test to exhaustion and two 60 min constant RPE rides at the RPE corresponding to the gas exchange threshold (RPEGET) and 15% above the GET (RPEGET+15%). Oxygen consumption (VO2), respiratory exchange ratio (RER), heart rate (HR), minute ventilation (VE), breathing frequency (FB), and power output (PO) were monitored throughout the rides. Polynomial regression analyses showed VO2, RER, HR, and VE (correlation = ā0.85 to ā0.98) tracked the decreases in PO required to maintain a constant RPE. Only FB tracked RPE during the moderate and heavy intensity rides. Repeated measures ANOVAs indicated that VO2 during the 60 min rides at RPEGET was not different (p \u3e 0.05) from VO2 at GET from the incremental test to exhaustion. Thus, monitoring intensity using an RPE associated with the GET is sustainable for up to 60 min of cycling exercise and a common mechanism may mediate FB and the perception of effort during moderate and heavy intensity cycle ergometry
Physiological Responses Underlying the Perception of Effort during Moderate and Heavy Intensity Cycle Ergometry
This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 Ā± 0.5 years; 43.4 Ā± 2.0 mLĀ·kgā1Ā·minā1 VO2Peak) moderately trained cyclists performed an incremental test to exhaustion and two 60 min constant RPE rides at the RPE corresponding to the gas exchange threshold (RPEGET) and 15% above the GET (RPEGET+15%). Oxygen consumption (VO2), respiratory exchange ratio (RER), heart rate (HR), minute ventilation (VE), breathing frequency (FB), and power output (PO) were monitored throughout the rides. Polynomial regression analyses showed VO2, RER, HR, and VE (correlation = ā0.85 to ā0.98) tracked the decreases in PO required to maintain a constant RPE. Only FB tracked RPE during the moderate and heavy intensity rides. Repeated measures ANOVAs indicated that VO2 during the 60 min rides at RPEGET was not different (p \u3e 0.05) from VO2 at GET from the incremental test to exhaustion. Thus, monitoring intensity using an RPE associated with the GET is sustainable for up to 60 min of cycling exercise and a common mechanism may mediate FB and the perception of effort during moderate and heavy intensity cycle ergometry
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