Transport of dietary cholesterol into blood and milk of the goat.

Position 4 labeled carbon-14 cholesterol was placed in abomasums (stomachs) of two lactating goats. Blood and milk samples were collected from the animals for 5 to 13 days. Specific activities of cholesterol and cholesteryl esters in various fractions of blood serum and milk were determined to reveal pathways by which dietary cholesterol enters milk. Results with the two animals showed similar trends. Within 24 h both cholesterol and cholesteryl esters of the three principal serum lipoproteins of the goat were labeled, and this labeling persisted in substantial degree for the 13-day experiment. Specific acities for cholesteryl esters in milk fat globules exhibited several remarkable attributes: they fluctuated in intensity with a 3-to 4-day cycle reaching a maximum at 7 to 8 days after tracer injection; they exceeded cholesteryl ester specific activity in the skim milk by an order of magnitude; and at their maximum they exceeded all specific activities for serum components. The results of this investigation exemplify the ease with which dietary cholesterol enters and crosses membranes in the animal body.     

Polyelectrolytes

Summary The polymerization of N,N-dimethyl-3,4-dimethylene-pyrrolidinium bromide was carried both in the presence and absence of initiators. Aqueous solutions with 10–50% monomer were polymerized by heating at 60°. The conversion time decreased with increased monomer concentration and molecular weight increased with increased monomer concentration. High monomer concentration also yielded significant amounts of monomer dimer.     

Derivatives of eigenvalues and eigenvectors of a general complex matrix

A survey of methods for sensitivity analysis of the algebraic eigenvalue problem for non-Hermitian matrices is presented. In addition, a modification of one method based on a better normalizing condition is proposed. Methods are classified as Direct or Adjoint and are evaluated for efficiency. Operation counts are presented in terms of matrix size, number of design variables and number of eigenvalues and eigenvectors of interest. The effect of the sparsity of the matrix and its derivatives is also considered, and typical solution times are given. General guidelines are established for the selection of the most efficient method.     

The Impact of Air Pollution on a Regional Economy

A study was made to determine a more comprehensive method of estimating the impact of an air pollutant on a region's economy. To do this, a Leontief input-output model of Clinton County, Pennsylvania was employed. Economic and related changes were simulated with the model by making appropriate changes and/or additions to the parameters of the model, i.e., the technical coefficients and elements of the external income input vector. In this specific application, the technical coefficients were represented by Direct Cost Response Functions in which the technical coefficient was a function of pollutant concentration. These functions were derived for the coefficients of all sectors whose expenditure pattern was affected by the pollutant. With these functions, it was possible to modify the base model to reflect the effect of different levels of pollutant concentration in the region. Economic impact studies yielding the direct and indirect changes in expenditures in all sectors of the model were then carried out showing the cost of air pollution damages to the region.     

Exercise tests before and after heart valve replacement

A simple progressive exercise test was performed before and after operation on five subjects undergoing mitral valve replacement and on five subjects undergoing aortic valve replacement. The responses of heart rate and ventilation were related to work rate )kilopond metres/min). The patients were also assessed clinically by the New York Heart Association grading and radiologically before each exercise test. The clinical grading was shown to be a poor guide to observed exercise tolerance, as the improvement noted in symptoms was not matched by the objective measurement of working capacity. Only two patients had normal exercise tolerance after surgery, although six of the ten patients claimed that they had no exertional dyspnoea after operation. The changes in simple ventilatory function tests before and after operation were generally small. We suggest that measurements of exercise tolerance before and after operation should be an essential part of heart valve replacement surgery.     

Techniques for thermal sensitivity analysis

Techniques for computing the sensitivity of temperatures to changes in design variables needed for designing thermal protection systems are considered. It is shown that the choice of the most efficient technique depends on the ratio of number of temperature constraints to the number of design variabies, as well as on the thermal analysis method employed. The analysis is specialized to the case of a structure modelled by finite elements, and an example of an insulation panel is used demonstrate the techniques.