Engineering topics
Publications and source records attributed to Taylor, Thomas D..
A system that automatically regulates the concentration of glucose or pH in a liquid culture medium that is circulated through a rotating-wall perfused bioreactor is described. Another system monitors the concentration of oxygen in the culture medium.
An optoelectronic instrument monitors the pH of an aqueous cell-culture medium in a perfused rotating-wall-vessel bioreactor. The instrument is designed to satisfy the following requirements: It should be able to measure the pH of the medium continuously with an accuracy of 0.1 in the range from 6.5 to 7.5. It should be noninvasive. Any material in contact with the culture medium should be sterilizable as well as nontoxic to the cells to be grown in the medium. The biofilm that inevitably grows on any surface in contact with the medium should not affect the accuracy of the pH measurement. It should be possible to obtain accurate measurements after only one calibration performed prior to a bioreactor cell run. The instrument should be small and lightweight. The instrument includes a quartz cuvette through which the culture medium flows as it is circulated through the bioreactor. The cuvette is sandwiched between light source on one side and a photodetector on the other side. The light source comprises a red and a green light-emitting diode (LED) that are repeatedly flashed in alternation with a cycle time of 5 s. The responses of the photodiode to the green and red LEDs are processed electronically to obtain a quantity proportional to the ratio between the amounts of green and red light transmitted through the medium.
Monitoring and regulating the pH of the solution in a bioprocess is one of the key steps in the success of bioreactor operation. An in-line optical pH sensor, based on the optical absorption properties of phenol red present in the medium, was developed and tested in this work for use in NASA space bioreactors based on a rotating wall-perfused vessel system supporting a baby hamster kidney (BHK-21) cell culture. The sensor was tested over three 30-day and one 124-day cell runs. The pH sensor initially was calibrated and then used during the entire cell culture interval. The pH reported by the sensor was compared to that measured by a fiber optically coupled Shimadzu spectrophotometer and a blood gas analyzer. The maximum standard error of prediction for all the four cell runs for development pH sensor against BGA was +/-0.06 pH unit and for the fiber optically coupled Shimadzu spectrophotometer against the blood gas analyzer was +/-0.05 pH unit. The pH sensor system performed well without need of recalibration for 124 days. Copyright 2002 Wiley Periodicals, Inc.
Mission operation concepts are described which are being used to evaluate and influence space and ground system designs and architectures with the goal of achieving successful, efficient, and cost-effective Earth Observing System (EOS) operations. Emphasis is given to the general characteristics and concepts developed for the EOS Space Measurement System, which uses a new series of polar-orbiting observatories. Data rates are given for various instruments. Some of the operations concepts which require a total system view are also examined, including command operations, data processing, data accountability, data archival, prelaunch testing and readiness, launch, performance monitoring and assessment, contingency operations, flight software maintenance, and security.
The architecture of the Earth Observing System (EOS), a major component of NASA's contribution to the U.S. Global Change Research Program, is described with emphasis on its development strategy. It is noted that the EOS is comprised of a scientific research program, a space measurement system, and an EOS Data and Information System (EOSDIS). Details are presented concerning the EOS program and its candidate instruments. Major components of EOS include Version 0 (V0) built on existing Distributed Active Archive Centers (DAACs), the EOSDIS core system (ECS), DAAC-unique functions, science computing facilities (SCF), and independent verification validation of the ECS. Requirements for EODIS are also reviewed noting that, among other requirements, it must keep up with an orbital average data rate of more than 30 Mbps as well as store, distribute, and manage information about tens of Petabytes of data during and after the 15-year mission.