Validation of a new spectrometer for noninvasive measurement of cardiac output

Acetylene is a blood-soluble gas and for many years its uptake rate during rebreathing tests has been used to calculate the flow rate of blood through the lungs (normally equal to cardiac output) as well as the volume of lung tissue. A new, portable, noninvasive instrument for cardiac output determination using the acetylene uptake method is described. The analyzer relies on nondispersive IR absorption spectroscopy as its principle of operation and is configured for extractive (side-stream) sampling. The instrument affords exceptionally fast (30 ms, 10%–90%, 90%–10%, at 500 mL min–1 flow rates), interference-free, simultaneous measurement of acetylene, sulfur hexafluoride (an insoluble reference gas used in the cardiac output calculation), and carbon dioxide (to determine alveolar ventilation), with good (typically ±2% full-scale) signal-to-noise ratios. Comparison tests with a mass spectrometer using serially diluted calibration gas samples gave excellent (R2>0.99) correlation for all three gases, validating the IR system's linearity and accuracy. A similar level of agreement between the devices also was observed during human subject C2H2 uptake tests (at rest and under incremental levels of exercise), with the instruments sampling a common extracted gas stream. Cardiac output measurements by both instruments were statistically equivalent from rest to 90% of maximal oxygen consumption; the physiological validity of the measurements was confirmed by the expected linear relationship between cardiac output and oxygen consumption, with both the slope and intercept in the published range. These results indicate that the portable, low-cost, rugged prototype analyzer discussed here is suitable for measuring cardiac output noninvasively in a point-of-care setting

Analytical and experimental investigation of mistuning in propfan flutter

An analytical and experimental investigation of the effects of mistuning on propfan subsonic flutter was performed. The analytical model is based on the normal modes of a rotating composite blade and a three-dimensinal subsonic unsteady lifting surface aerodynamic theory. Theoretical and experimental results are compared for selected cases at different blade pitch angles, rotational speeds, and free-stream Mach numbers. The comparison shows a reasonably good agreement between theory and experiment. Both theory and experiment showed that combined mode shape, frequency, and aerodynamic mistuning can have a beneficial or adverse effect on blade damping depending on Mach number. Additional parametric results showed that alternative blade frequency mistuning does not have enough potential for it to be used as a passive flutter control in propfans similar to the one studied. It can be inferred from the results that a laminated composite propfan blade can be tailored to optimize its flutter speed by selecting the proper ply angles

Artificial photosynthesis: semiconductor photocatalytic fixation of CO_2 to afford higher organic compounds

Carbon dioxide is an appealing renewable feedstock for industrial chemical processes. This does not mean, however, that all chemical processes using CO_2 are environmentally-friendly. Perspectives on the sustainability of CO_2 utilization and artificial photosynthesis are provided. The discussions focus on the photocatalytic production of C_x (x ≥ 2) compounds, where all the carbon in the products is derived from CO_2. This area of research, while promising, has received far less attention than analogous systems leading to C_1 products

Numerical modelling of two-way reinforced concrete slabs in fire

This paper describes numerical modelling of the fire behaviour of two-way reinforced concrete slabs using a special purpose non-linear finite-element program, SAFIR. Several two-way reinforced concrete and composite steel-concrete slabs are tested under exposure to the ISO standard fire in order to validate the shell finite element in the SAFIR program. The modelling results showed agreement with the fire tests and demonstrate that the SAFIR shell element can be used to predict tensile membrane behaviour of two-way reinforced concrete slabs in fire conditions. The analyses show that two-way slabs have excellent fire resistance if they deform in double curvature and develop tensile membrane action. (C) 2004 Elsevier Ltd. All rights reserved

Extravascular lung water in patients with severe sepsis: a prospective cohort study

INTRODUCTION: Few investigations have prospectively examined extravascular lung water (EVLW) in patients with severe sepsis. We sought to determine whether EVLW may contribute to lung injury in these patients by quantifying the relationship of EVLW to parameters of lung injury, to determine the effects of chronic alcohol abuse on EVLW, and to determine whether EVLW may be a useful tool in the diagnosis of acute respiratory distress syndrome (ARDS). METHODS: The present prospective cohort study was conducted in consecutive patients with severe sepsis from a medical intensive care unit in an urban university teaching hospital. In each patient, transpulmonary thermodilution was used to measure cardiovascular hemodynamics and EVLW for 7 days via an arterial catheter placed within 72 hours of meeting criteria for severe sepsis. RESULTS: A total of 29 patients were studied. Twenty-five of the 29 patients (86%) were mechanically ventilated, 15 of the 29 patients (52%) developed ARDS, and overall 28-day mortality was 41%. Eight out of 14 patients (57%) with non-ARDS severe sepsis had high EVLW with significantly greater hypoxemia than did those patient with low EVLW (mean arterial oxygen tension/fractional inspired oxygen ratio 230.7 ± 36.1 mmHg versus 341.2 ± 92.8 mmHg; P < 0.001). Four out of 15 patients with severe sepsis with ARDS maintained a low EVLW and had better 28-day survival than did ARDS patients with high EVLW (100% versus 36%; P = 0.03). ARDS patients with a history of chronic alcohol abuse had greater EVLW than did nonalcoholic patients (19.9 ml/kg versus 8.7 ml/kg; P < 0.0001). The arterial oxygen tension/fractional inspired oxygen ratio, lung injury score, and chest radiograph scores correlated with EVLW (r(2 )= 0.27, r(2 )= 0.18, and r(2 )= 0.28, respectively; all P < 0.0001). CONCLUSIONS: More than half of the patients with severe sepsis but without ARDS had increased EVLW, possibly representing subclinical lung injury. Chronic alcohol abuse was associated with increased EVLW, whereas lower EVLW was associated with survival. EVLW correlated moderately with the severity of lung injury but did not account for all respiratory derangements. EVLW may improve both risk stratification and management of patients with severe sepsis

Methods and challenges of experimental system identification of a distillation column

University of Tennessee at Chattanooga Engineering Department distillation column is used as a teaching tool, but is currently without a feedback control system. An eventual goal of developing such a control system requires that the behavior of the column be understood. It is necessary to identify which of the column parameters can change, either ones that change to cause a disturbance, or ones that the controller can change in response to a disturbance. There are four of these parameters in the UTC column: feed flow rate, feed composition, reboiler heat and reflux percent. Experiments were performed on the column to identify the response when each of the four parameters was changed in isolation. A chart showing the concentrations on each of the trays both before and after the change was used to visualize how the change affected the individual trays. The operating lines from the McCabe-Thiele method were used to analyze the overall effect on the column. An analysis of the speed of the response of the individual trays was also performed. From these methods of analysis, it is apparent that the center of the column responds most quickly to a disturbance. Three experiments were also performed in which manual feedback control schemes were tested on the column. In all three cases, the goal was to maintain one of the product streams at the starting concentration after a disturbance by manipulating only one of the controllable parameters, the reboiler heat

Employers\u27 Perceptions of Intimate Partner Violence among a Diverse Workforce

Objectives Intimate partner violence (IPV) is a significant global public health concern, affecting 5.3 million US individuals annually. An estimated 1 in 3 women globally are abused by an intimate partner in their lifetime, and the effects carry over into the workplace. This article examines employers\u27 perceptions of IPV in the workplace, targeting supervisors of Latina employees. Methods Fourteen employers and supervisors of small service-sector companies in Oregon were interviewed using semi-structured interviews. Interpretive description was used to identify themes. These qualitative interviews preceded and helped to formulate a larger workplace intervention study. Results The following themes were found and are detailed: (1) factors associated with recognizing IPV in the workplace, (2) effects of IPV on the work environment and (3) supervisors\u27 responses to IPV-active vs. passive involvement. Also, supervisors\u27 suggestions for addressing IPV in the workplace are summarized. Conclusion These findings demonstrate the need for more IPV-related resources in the workplace to be available to supervisors as well as survivors and their coworkers. The needs of supervisors and workplaces vary by site, demonstrating the need for tailored interventions, and culturally appropriate workplace interventions are needed for Latinas and other racially and ethnically diverse populations