Relative Position Model Predictive Control of Double Cube Test-Masses Drag-Free Satellite with Extended Sliding Mode Observer

The drag-free satellites, being space-borne ultrahigh precise measurement platforms, have played irreplaceable roles in a great number of space science missions such as navigation, earth science, fundamental physics, and astrophysics. Most of these missions have to be performed based on the satellites placed with double cube test-masses, which makes the satellite layout and control strategy be more complex. This paper investigates the orbit keeping control problem of a class of low Earth orbit drag-free satellites with double cube test masses. A disturbance observer-based composite control method is proposed, which consists of an extended sliding mode observer and the tube-based robust model predictive control approach. In this design, the observer is proposed to estimate the relative position and velocity of the satellite and the external space disturbance force. A tube-based robust model predictive control scheme is then developed to stabilize the satellite orbit control systems in the presence of actuator saturation, state constraints, and additive stochastic noises. Finally, a simulation example is presented to demonstrate the efficacy and superiority of the proposed orbit control method

Breath pentane: an indicator for early and continuous monitoring of lipid peroxidation in hepatic ischaemia-reperfusion injury

Background and objective Lipid peroxidation plays an important role during liver ischaemia-reperfusion injury. Pentane in breath is often used as an index of lipid peroxidation. We observed the changes in levels of breath pentane during the lipid peroxidation process caused by liver ischaemia-reperfusion injury

Original Article Effects of different types of hydroxyethyl starch (HES) on microcirculation perfusion and tissue oxygenation in patients undergoing liver surgery

Abstract: To compare the effects of hydroxyethyl starch (HES) 130/0.4 and HES 200/0.5, which have different molecular weights and degrees of substitution, on microcirculation perfusion and tissue oxygenation in patients undergoing liver surgery. Thirty patients with an American Society of Anesthesiologists status I/II who were scheduled for liver surgery were randomly divided into two groups: one received an intraoperative HES 130/0.4 infusion equal to the amount of blood loss (HES 130/0.4 group, n=15), and the other received HES 200/0.5 equal to the amount of blood loss (HES 200/0.5 group, n=15). Gastric mucosal perfusion and tissue oxygenation were monitored by measuring the gastric mucosal pH (pH i ), which was determined using a carbon dioxide tonometer inserted through a nasogastric tube. Gastric mucosal pH i , hemodynamic parameters, body temperature, and blood gas parameters were recorded upon entering the operating room, before skin incision, one hour and two hours after skin incision, and at the end of surgery. The intraoperative pH i decreased in both groups of patients, but the decline in the HES 130/0.4 group was smaller than that of the HES 200/0.5 group. The pH i of the HES 130/0.4 group was significantly higher than that of the HES 200/0.5 group two hours after skin incision and at the end of surgery (P<0.05). A multivariate analysis showed that the type of colloid used intraoperatively was the only variant that affected pH i (F=0.626, P<0.05). Moreover, there were good correlation between pH i at the end of surgery and the length of postoperative hospital stay (r=-0.536, P<0.05) and the time intervals from surgery to the passage of flatus (r=-0.547, P<0.05). Compared with HES 200/0.5, the use of HES 130/0.4 (with a relatively lower molecular weight and lower degree of substitution) could significantly improve internal organ perfusion and tissue oxygenation in patients undergoing liver surgery with a relatively large amount of blood loss

Time-resolved dynamic dilution introduction for ion mobility spectrometry and its application in end-tidal propofol monitoring

Based on the adsorption of analytes in the sampling loop, a time-resolved dynamic dilution introduction method was developed for negative ion mobility spectrometry to continuously monitor end-tidal propofol without other sample pre-separation. The dynamic dilution characteristics of propofol and moisture in the Teflon sample loop (4 mm o. d. and 2.4 mm i. d., 150 cm length) were both theoretically and experimentally investigated. The prominent absorption differences between propofol and moisture on the inwall of the sample loop allowed their concentrations to be time-resolved during the injection process, realizing sensitive measurement of end-tidal propofol with a response time of 2 s. At the optimized carrier gas flow rate of 700 mL min(-1), the linear response range for propofol was achieved to be 0.2 to 20 ppbv with a limit of detection (LOD) of 65 pptv. Finally, this method was performed on a patient undergoing mastectomy surgery to continuously monitor the end-tidal propofol with an interval of five respirations and the result nicely demonstrated its fast response to the propofol changes

Online Monitoring of Intraoperative Exhaled Propofol by Acetone-Assisted Negative Photoionization Ion Mobility Spectrometry Coupled with Time-Resolved Purge Introduction

Online monitoring of exhaled propofol concentration is important for anesthetists to provide adequate anesthesia as propofol concentrations in plasma and breath are correlated reasonably well. Exhaled propofol could be detected by Ni-63 ion mobility spectrometry in negative ion mode; however, the radioactivity of Ni-63 source restricts its clinical application due to safety, environmental, and regulatory concerns. An acetone-assisted negative photoionization ion mobility spectrometer (AANP-IMS) using a side-mounted vacuum ultraviolet (VUV) lamp in the unidirectional (UD) flow mode was developed for sensitive measurement of exhaled propofol by producing a high percentage of O-2(-)(H2O)(n). An adsorption sampling and time-resolved purge introduction system was developed to eliminate the interference of residual inhaled anesthetic sevoflurane based on their different adsorptions between propofol and sevoflurane on the inwall of the fluorinated ethylene propylene (FEP) sample loop. The effects of the inner diameter and the length of the sample loop on the signal intensity of propofol and the time-resolution between propofol and sevoflurane were theoretically and experimentally investigated. A sample loop with 3 mm i.d. and 150 cm length allowed sensitive measurement of exhaled propofol with a response time of 4 s, a linear response range for propofol was achieved to be 0.2 to 14 ppbv with a limit of detection (LOD) of 60 pptv, and the quantification of propofol was not influenced by the change of the sevoflurane concentration. Finally, the performance of monitoring exhaled propofol during surgery was demonstrated on a patient undergoing laparoscopic distal pancreatectomy combined with cholecystectomy

Dopant titrating ion mobility spectrometry for trace exhaled nitric oxide detection

Ion mobility spectrometry (IMS) is a promising non-invasive tool for the analysis of exhaled gas and exhaled nitric oxide (NO), a biomarker for diagnosis of respiratory diseases. However, the high moisture in exhaled gas always brings about extra overlapping ion peaks and results in poor identification ability. In this paper, p-benzoquinone (PBQ) was introduced into IMS to eliminate the interference of overlapping ion peaks and realize the selective identification of NO. The overlapping ions caused by moisture were titrated by PBQ and then converted to hydrated PBQ anions (C6H4O2-(H2O)(n)). The NO concentration could be determined by quantifying gas phase hydrated nitrite anions (NO2-(H2O)(n)), product ions of NO. Under optimized conditions, a limit of detection (LOD) of about 1.4 ppbv and a linear range of 10-200 ppbv were obtained for NO even in 100% relative humidity (RH) purified air. Furthermore, this established method was applied to measure hourly the exhaled NO of eight healthy volunteers, and real-time monitoring the exhaled NO of an esophageal carcinoma patient during radical surgery. These results revealed the potential of the current dopant titrating IMS method in the measurement of exhaled NO for medical disease diagnosis

Effects of Propofol on Several Membrane Characteristics of Cervical Cancer Cell Lines

Background: Although significant advances have been made toward understanding the molecular mechanisms underlying the effect of propofol on tumor cell metastasis, less is known regarding how cell membrane and cytoskeletal ultrastructure are affected in this process. Here, we investigated the relationship between cell morphology and cell size, which are features mainly defined by the cytoskeleton. Methods: To confirm the effects of propofol on the migratory ability of human cervical carcinoma cells, cell migration and invasion were examined through scratch wound healing and transwell membrane assays. Furthermore, HeLa cells cultivated with different concentrations of propofol were examined by confocal microscopy and atomic force microscopy (AFM), and the mean optical density and migration ability of these cells were also assessed. In addition, cell membrane morphology was inspected using AFM. Results: The results of the wound healing and transwell membrane assays indicated that propofol decreases the migratory ability of cervical carcinoma cells compared to control cells. A comparative analysis of the test results revealed that short-term (3 h) exposure to propofol induced marked changes in cell membrane microstructure and in the cytoskeleton in a dose-dependent manner. These morphological changes in the cell membrane were accompanied by cytoskeleton (F-actin) derangement. The present findings demonstrate a close relationship between changes in cell membrane ultrastructure and cytoskeletal alterations (F-actin) in propofol-treated HeLa cells. AFM scanning analysis showed that cell membrane ultrastructure was significantly changed, including a clear reduction in membrane roughness. Conclusion: The influence of propofol on the HeLa cell cytoskeleton can be directly reflected by changes in cellular morphology, as assessed by AFM. Moreover, the use of AFM is a good method for investigating propofol-mediated changes within cytoskeletal ultrastructure