1,298 research outputs found
Model predictive control using MISO approach for drug co-administration in anesthesia
In this paper, a model predictive control system for the depth of hypnosis is proposed and analyzed. This approach considers simultaneous co-administration of the hypnotic and analgesic drugs and their effect on the Bispectral Index Scale (BIS). The control scheme uses the nonlinear multiple-input–single-output (MISO) model to predict the remifentanil influence over the propofol hypnotic effect. Then, it exploits a generalized model predictive control algorithm and a ratio between the two drugs in order to provide the optimal dosage for the desired BIS level, taking into account the typical constraints of the process. The proposed approach has been extensively tested in simulation, using a set of patients described by realistic nonlinear pharmacokinetic/pharmacodynamic models, which are representative of a wide population. Additionally, an exhaustive robustness evaluation considering inter- and intra-patient variability has been included, which demonstrates the effectiveness of the analyzed control structure
Diffuse -ray emission from misaligned active galactic nuclei
Active galactic nuclei (AGN) with jets seen at small viewing angles are the
most luminous and abundant objects in the -ray sky. AGN with jets
misaligned along the line-of-sight appear fainter in the sky, but are more
numerous than the brighter blazars. We calculate the diffuse -ray
emission due to the population of misaligned AGN (MAGN) unresolved by the Large
Area Telescope (LAT) on the {\it Fermi} Gamma-ray Space Telescope ({\it
Fermi}). A correlation between the -ray luminosity and the radio-core
luminosity is established and demonstrated to be physical by statistical tests,
as well as compatible with upper limits based on {\it Fermi}-LAT data for a
large sample of radio-loud MAGN. We constrain the derived -ray
luminosity function by means of the source count distribution of the radio
galaxies (RGs) detected by the {\it Fermi}-LAT. We finally calculate the
diffuse -ray flux due to the whole MAGN population. Our results
demonstrate that the MAGN can contribute from 10% up to nearly the entire
measured Isotropic Gamma-Ray Background (IGRB). We evaluate a theoretical
uncertainty on the flux of almost an order of magnitude.Comment: Accepted for publication in Ap
Reading a GEM with a VLSI pixel ASIC used as a direct charge collecting anode
In MicroPattern Gas Detectors (MPGD) when the pixel size is below 100 micron
and the number of pixels is large (above 1000) it is virtually impossible to
use the conventional PCB read-out approach to bring the signal charge from the
individual pixel to the external electronics chain. For this reason a custom
CMOS array of 2101 active pixels with 80 micron pitch, directly used as the
charge collecting anode of a GEM amplifying structure, has been developed and
built. Each charge collecting pad, hexagonally shaped, realized using the top
metal layer of a deep submicron VLSI technology is individually connected to a
full electronics chain (pre-amplifier, shaping-amplifier, sample and hold,
multiplexer) which is built immediately below it by using the remaining five
active layers. The GEM and the drift electrode window are assembled directly
over the chip so the ASIC itself becomes the pixelized anode of a MicroPattern
Gas Detector. With this approach, for the first time, gas detectors have
reached the level of integration and resolution typical of solid state pixel
detectors. Results from the first tests of this new read-out concept are
presented. An Astronomical X-Ray Polarimetry application is also discussed.Comment: 11 pages, 14 figures, presented at the Xth Vienna Conference on
Instrumentation (Vienna, February 16-21 2004). For a higher resolution paper
contact [email protected]
Event-Based control of depth of hypnosis in anesthesia
Background and Objective: In this paper, we propose the use of an event-based control strategy for the closed-loop control of the depth of hypnosis in anesthesia by using propofol administration and the bispectral index as a controlled variable. Methods: A new event generator with high noise-filtering properties is employed in addition to a PIDPlus controller. The tuning of the parameters is performed off-line by using genetic algorithms by considering a given data set of patients. Results: The effectiveness and robustness of the method is verified in simulation by implementing a Monte Carlo method to address the intra-patient and inter-patient variability. A comparison with a standard PID control structure shows that the event-based control system achieves a reduction of the total variation of the manipulated variable of 93% in the induction phase and of 95% in the maintenance phase. Conclusions: The use of event based automatic control in anesthesia yields a fast induction phase with bounded overshoot and an acceptable disturbance rejection. A comparison with a standard PID control structure shows that the technique effectively mimics the behavior of the anesthesiologist by providing a significant decrement of the total variation of the manipulated variable
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