Awareness of language in children who have reading difficulties: historical comparisons in a longitudinal study

The purpose of this study was to assess factors associated with the use of family planning at first sexual intercourse among young adults aged 15 to 24 in urban Ecuador. The study population consisted of 1443 young adults (494 females and 949 males) in the cities of Quito and Guayaquil, interviewed by the 1988 Ecuador Young Adult Reproductive Health Survey, who reported having experienced consensual sexual intercourse. Approximately 11% of females and 15% of males reported using contraception at first intercourse. Binary logistic regression was performed to assess jointly the effect of multiple factors on contraceptive use at first intercourse. The regression model was first run on the entire study population and then separately for males and females. In the overall population, the following variables were significantly related to using family planning at first sex: being male; being from Guayaquil; older age; father's completion of secondary school. Having lost one's virginity to a prostitute was significantly associated with non-use of family planning. Males were 3.6 times more likely than females to use family planning during their first sexual intercourse. For each year older a young adult was at first sex, his or her odds of using family planning was multiplied by a factor of 1.3. Twenty-eight per cent of males in this study experienced their first sexual intercourse with a prostitute, and these young men were highly unlikely to use family planning. A male who experienced first intercourse with his girlfriend was more than five times as likely to use contraception than a male who lost his virginity to a prostitute.     

Method for Measuring Dipole Parameters of Isolated Hearts and Muscles?Application to Frog Gastrocnemius

Resistor networks were developed to measure the magnitude, direction, and location of the resultant dipole moment of isolated hearts or muscles located at the center of a fluid-filled dish. With the network connected to the dish electrodes, these quantities could be determined from only four bipolar voltage measurements. Energized muscle strips were simulated by dipping pieces of metal of different lengths into the electrolyte. The resultant location was found to be midway between the centers of the two pieces, rather than at the gap between them.     

Isolation of a spotted fever group rickettsia from the Pacific Coast tick, Ixodes pacificus, in Oregon

A rickettsia of the spotted fever group was isolated on three occasions from Ixodes pacificus in western Oregon. These isolations, and additional evidence furnished by complement fixation tests on guinea pigs inoculated with other Oregon ticks of this species, indicate that the association of this rickettsia with the Pacific Coast tick may be widespread. This is the first isolation of a spotted fever group rickettsia from I. pacificus. Because the Oregon isolates are mildly virulent for guinea pigs they resemble the Western U and Rickettsia montana strains of rickettsiae. However, preliminary evidence from cross-immunofluorescence tests of mouse antisera suggests the Tillamook and Grants Pass strains are antigenically different from all known spotted fever group agents.     

A Capital Budgeting Heuristic Algorithm Using Exchange Operations

A heuristic algorithm for solving capital budgeting problems is described. The algorithm proceeds from an initial solution, obtained with the use of ranking procedures, and progressively improves the solution through exchange operations. Computational experience in solving a set of 30-variable, 5-constraint problems is described and the approach to optimal values with increasing computation time is shown. The results show considerable time advantage over 0-1 implicit enumeration techniques. In only two of twenty-eight problems were the solutions nonoptimal, and in these two cases the objective function values for the heuristic solutions were within 0.5 percent of those for the optimal solutions. A brief investigation was conducted on larger problems (60 variables, 5 constraints); the time advantage is even greater on problems of that size. Details of the problems and their optimal solutions are available to interested readers upon request to the author.     

Phosphorus removal in the activated sludge process

The results from this research suggest that both calcium phosphate precipitation and enhanced biological uptake play a role in phosphorus removal in the activated sludge process when a non-nitrifying, anaerobic-aerobic system is used to treat a low calcium wastewater. The primary removal mechanism was found to be biological uptake, as calcium phosphate precipitation accounted for only 15–27% of the total phosphorus removed. Calcium phosphate precipitation in the aerobic unit was enhanced because of the pH increase in that reactor. This was the result of low CO₂ production (indicated by low specific oxygen uptake values) and intense aeration which caused excessive CO₂ stripping in the aerobic unit     

Thermal model of a cylindrically symmetric solar pond

A finite element heat transport program has been modified to model the thermal behavior for a cylindrically symmetric salt gradient polar pond of the Rabl-Nielsen type. In this model transient phenomena as well as steady state behavior can be studied. Results are presented for a model of the solar pond at the University of New Mexico and are compared with actual measurements.