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Background Genome-scale metabolic networks and flux models are an effective platform for linking an organism genotype to its phenotype. However, few modeling approaches offer predictive capabilities to evaluate potential metabolic engineering strategies in silico. Results A new method called “flux balance analysis with flux ratios (FBrAtio)” was developed in this research and applied to a new genome-scale model of Clostridium acetobutylicum ATCC 824 (iCAC490) that contains 707 metabolites and 794 reactions. FBrAtio was used to model wild-type metabolism and metabolically engineered strains of C. acetobutylicum where only flux ratio constraints and thermodynamic reversibility of reactions were required. The FBrAtio approach allowed solutions to be found through standard linear programming. Five flux ratio constraints were required to achieve a qualitative picture of wild-type metabolism for C. acetobutylicum for the production of: (i) acetate, (ii) lactate, (iii) butyrate, (iv) acetone, (v) butanol, (vi) ethanol, (vii) CO2 and (viii) H2. Results of this simulation study coincide with published experimental results and show the knockdown of the acetoacetyl-CoA transferase increases butanol to acetone selectivity, while the simultaneous over-expression of the aldehyde/alcohol dehydrogenase greatly increases ethanol production. Conclusions FBrAtio is a promising new method for constraining genome-scale models using internal flux ratios. The method was effective for modeling wild-type and engineered strains of C. acetobutylicum.

Background Genome-scale metabolic networks and flux models are an effective platform for linking an organism genotype to its phenotype. However, few modeling approaches offer predictive capabilities to evaluate potential metabolic engineering strategies in silico. Results A new method called “flux balance analysis with flux ratios (FBrAtio)” was developed in this research and applied to a new genome-scale model of Clostridium acetobutylicum ATCC 824 (iCAC490) that contains 707 metabolites and 794 reactions. FBrAtio was used to model wild-type metabolism and metabolically engineered strains of C. acetobutylicum where only flux ratio constraints and thermodynamic reversibility of reactions were required. The FBrAtio approach allowed solutions to be found through standard linear programming. Five flux ratio constraints were required to achieve a qualitative picture of wild-type metabolism for C. acetobutylicum for the production of: (i) acetate, (ii) lactate, (iii) butyrate, (iv) acetone, (v) butanol, (vi) ethanol, (vii) CO2 and (viii) H2. Results of this simulation study coincide with published experimental results and show the knockdown of the acetoacetyl-CoA transferase increases butanol to acetone selectivity, while the simultaneous over-expression of the aldehyde/alcohol dehydrogenase greatly increases ethanol production. Conclusions FBrAtio is a promising new method for constraining genome-scale models using internal flux ratios. The method was effective for modeling wild-type and engineered strains of C. acetobutylicum.

This report presents summary descriptions of the research projects performed by Anacapa Sciences, Inc., for the U.S. Army Research Institute Aviation Research and Development Activity (ARIARDA) at Fort Rucker, Alabama, under Contract No. MDA903-87-C-0523, entitled 'Human Factors Research in Aircrew Performance and Training.' From 9 October 1988 to 8 October 1989, Anacapa personnel worked on 31 research projects and 4 technical advisory services in emerging aviation weapon systems design, manpower and personnel programs, aviator training, and aviation safety research. The summary description for each project and technical advisory service contains a background section that describes the rationale for the project and specifies the research objectives; a research approach section that describes the tasks and activities required to meet the project objectives; a research findings section or, in the case of developmental activities, a research products section; and a project status section that describes projections for future research, if any. (eg)

This research note presents summary descriptions of research projects performed for ARI at Fort Rucker, Alabama. During the period 18 February 1986 through 8 October 1987, contractor personnel worked on 17 research projects in the areas of emerging system design, manpower and personnel, aviation simulation, and aviator training. The summary description for each project contains a background section that describes the rationale for the project, and specifies the research objectives, a research approach section that describes the tasks and activities required to meet the project objectives, a results section describing the research findings (or, in the case of developmental activities, the research products), and, finally, a project status section that describes the work completed and projections for future research, if any. Keywords: Helicopter flight simulation; Computer based instruction; Aviation selection training; Aviation skill decay; Aviation training; Sensors and symbology.

In November 1983, the syllabus for the Flight Surgeon flight training program was changed from a solo flight to a formal checkride evaluation at the 14-hour level. A preliminary investigation indicated that the syllabus change might negatively affect the training program by reducing its attractiveness to potential applicants or by reducing student attitude, motivation, and performance during flight training. During 1984, all Flight Surgeon students completed an 'Incentive Factors Survey' before beginning the course. After completing the course, the instructor pilots rated each of their students on a 'Flight Training Survey'. The most important application incentives to the majority of the Flight Surgeon students were the opportunities to enhance their military careers, to receive flight training, and to study aviation medicine. The opportunity to fly solo was an important, positive incentive to 22% of the students, but 31% of the students were either indifferent to or negatively influenced by a solo flight opportunity. The remaining 47% of the students indicated that the solo flight opportunity was a modest, positive incentive. The flight training ratings indicated that student attitudes and motivation levels were not only satisfactory, but were generally above average when compared to previous Flight Surgeon students. Ratings of student performance were generally commensurate with ratings of the student's ability.