Nutritional criteria in machiguenga food production decisions: A linear-programming analysis

Machiguenga Indians of the Peruvian Amazon, like other low populationdensity, technologically “simple” peoples, produce ample food for a nutritious diet. Assuming that this is an intended outcome of their foodproduction strategy, to what extent is it a labor-efficient solution to the problem of producing a “balanced diet”? A linear-programming model of the “diet problem” is constructed with parameters reflecting the Machiguenga economy, and solutions are computed. These are then compared to observed Machiguenga food production; the degree of fit between model and behavior is examined and reasons for discrepancies are discussed.     

Computer control of fermentation processes

A review of computer control of fermentation processes is presented. Hardware and software technologies that have been used to implement computer control are discussed. This includes instrumentation, interfacing techniques, computer hardware configurations, data logging and documentation, displays and man-machine interaction, low-level control, back-up and error detection and programming techniques. Advanced control of fermentation processes with the utilization of modern control techniques is also presented. This topic is divided into steady state optimization and dynamic optimization. Finally, on-line estimation of bioreactor parameters for feedback control is presented.     

Anti-viral activity of 3-deazaadenosine and 5'-deoxy-5'-isobutylthio-3-deazaadenosine (3-deaza-SIBA)

3-Deazaadenosine and 5′-deoxy-5′-isobutylthio-3-deazaadenosine (3-deaza-SIBA) inhibits replication of both herpes simplex type 1 virus and the RNA type C virus, HL-23. Oncogenic transformation caused by SV40 and HL-23 are also blocked by either compound. Both compounds exhibit relatively low cytotoxicity at the anti-viral concentrations.     

Thymidine kinase activity in mouse embryo fibroblast cells infected with murine cytomegalovirus

Thymidine kinase activity was found in whole cell extracts of growing and stationary mouse embryo fibroblast cells after infection with murine cytomegalovirus. Determination of the kinetic constants and heat stability characteristics indicated that the enzyme activity from infected cells was different to that found in uninfected cells in the growth phase. The expression of thymidine kinase activity during virus replication was reflected by the incorporation of (6-³H) thymidine into acid precipitable fractions of infected cell cultures. Preliminary data from kinetic studies showed a reduction in the phosphorylation of thymidine by this enzyme activity in the presence of Acyclovir, a potent inhibitor of herpes virus replication.     

Parameter identification of the calvin photosynthesis cycle

Summary This article is concerned with the determination of kinetic parameters of the Calvin photosynthesis cycle which is described by seventeen nonlinear ordinary differential equations. It is shown that the task requires dynamic data for several sets of initial conditions. The numerical technique is based upon an algorithm for non-linear optimization and Gear's numerical integration scheme for stiff systems of differential equations. The sensitivity of the parameters to noise in the data is tested with a method adapted from Rosenbrook and Storey. A preliminary set of parameters has been obtained from a preliminary set of experimental data. The numerical methods are then tested with synthetic data derived from these parameters. The mathematical model and the results obtained in the simulation are used as an aid in designing new experiments.     

Antimetabolic activities of 2-fluoro-L-histidine.

2-Fluoro-L-Histidine inhibits protein synthesis in various cell cultures, as measured by ³H-leucine incorporation. This histidine analog also inhibits the cytopathogenicity of a number of RNA and DNA viruses in primary and continuous cell cultures; it blocks the transformation of normal mouse (MO) cells by murine sarcoma virus, and partially suppresses the release of murine leukemia virus by a continuously infected mouse cell line (JLSV5). In human skin fibroblasts, it reduces the interferon-inducing capacity of poly(I)·poly(C). Inhibition of cell protein synthesis may be the common cause of the various effects. 4-Fluoro-L-histidine is essentially inert in all of the test systems examined.     

POLYOL DEHYDROGENASE: PURIFICATION. EVIDENCE FOR MULTIPLE FORMS AND SOME PROPERTIES OF THE DOMINANT VARIANT OF THE HORSE LIVER ENZYME

Purification of horse-liver polyoi dehydrogenase (PDH) on DE52 anion-exchange cellulose reveals the presence of three fractions with enzyme activity. These appear in the breakthrough volume (PDH-3) and the salt gradient (PDH-1, -2) respectively. The major band of activity (< 90%) is found in the PDH-2 fraction. A reexamination of sheep-liver polyol dehydrogenase also reveals the presence of three bands of activity, with the dominant fraction (PDH-3) corresponding to the preparation described by Smith (Biochem. J., 83, 135–144, (1962))³. The interaction between horse-liver (and sheep-liver) PDH and Blue Sepharose CL-6B is found to be endothermic. This property is utilized in the final purification step. Horse-liver PDH-2 has a molecular/subunit weight of 85, 000/28, 000, a Stokes' radius of 3.8 nm, and an isoelectric point of 7.4.     

Characterization of robust optimization for VMAT plan for liver cancer

PurposeWe investigated the feasibility of robust optimization for volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) for liver cancer in comparison with planning target volume (PTV)-based optimized plans. Treatment plan quality, robustness, complexity, and accuracy of dose delivery were assessed.MethodsTen liver cancer patients were selected for this study. PTV-based optimized plans with an 8-mm PTV margin and robust optimized plans with an 8-mm setup uncertainty were generated. Plan perturbed doses were evaluated using a setup error of 8 mm in all directions from the isocenter. The dosimetric comparison parameters were clinical target volume (CTV) doses (D_98%, D_50%, and D_2%), liver doses, and monitor unit (MU). Plan complexity was evaluated using the modulation complexity score for VMAT (MCSv).ResultsThere was no significant difference between the two optimizations with respect to CTV doses and MUs. Robust optimized plans had a higher liver dose than did PTV-based optimized plans. Plan perturbed dose evaluations showed that doses to the CTV for the robust optimized plans had small variations. Robust optimized plans were less complex than PTV-based optimized plans. Robust optimized plans had statistically significant fewer leaf position errors than did PTV-based optimized plans.ConclusionsComparison of treatment plan quality, robustness, and plan complexity of both optimizations showed that robust optimization could be feasibile for VMAT of liver cancer.