Using the late spring nitrate test to reduce nitrate loss within a watershed.

Excessive nitrate leaching from the U.S. Corn Belt has created serious water quality problems and contributed to the expansion of the hypoxic zone in the Gulf of Mexico. We evaluated the effect of implementing the late spring nitrate test (LSNT) for corn (Zea mays L.) grown within a 400-ha, tile-drained subbasin in central Iowa. Surface water discharge and NO3 concentrations from the treated subbasin and two adjacent subbasins receiving primarily fall-applied, anhydrous ammonia were compared. In two of four years, the LSNT method significantly reduced N fertilizer applications compared with the farmers' standard practices. Average corn yield from LSNT fields and nonlimiting N fertilizer check strips was not significantly different. Autoregressive (AR) models using weekly time series in surface water NO3 concentration differences between the LSNT and control subbasins indicated no consistent significant differences during the pre-LSNT (1992-1996) period. However, by the second year (1998) of the treatment period (1997-2000), NO3 concentrations in surface water from the treated subbasin were significantly lower than the concentrations coming from both control basins. Annual average flow-weighted NO3 concentrations for the last two years (1999-2000) were 11.3 mg N L(-1) for the LSNT and subbasin and 16.0 mg N L(-1) for the control subbasins. Based on these values and the AR models, widespread adoption of the LSNT program for managing N fertilizer where fall N application is typically practiced could result in a > or = 30% decrease for NO3 concentrations in surface water.

Nitrate loss in subsurface drainage as affected by nitrogen fertilizer rate.

The relationships between N fertilizer rate, yield, and NO3 leaching need to be quantified to develop soil and crop management practices that are economically and environmentally sustainable. From 1996 through 1999, we measured yield and NO3 loss from a subsurface drained field in central Iowa at three N fertilizer rates: a low (L) rate of 67 kg ha(-1) in 1996 and 57 kg ha(-1) in 1998, a medium (M) rate of 135 kg ha(-1) in 1996 and 114 kg ha(-1) in 1998, and a high (H) rate of 202 kg ha(-1) in 1996 and 172 kg ha(-1) in 1998. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were grown in rotation with N fertilizer applied in the spring to corn only. For the L treatment, NO3 concentrations in the drainage water exceeded the 10 mg N L(-1) maximum contaminant level (MCL) established by the USEPA for drinking water only during the years that corn was grown. For the M and H treatments, NO3 concentrations exceeded the MCL in all years, regardless of crop grown. For all years, the NO3 mass loss in tile drainage water from the H treatment (48 kg N ha(-1)) was significantly greater than the mass losses from the M (35 kg N ha(-1)) and L (29 kg N ha(-1)) treatments, which were not significantly different. The economically optimum N fertilizer rate for corn was between 67 and 135 kg ha(-1) in 1996 and 114 and 172 kg ha(-1) in 1998, but the net N mass balance indicated that N was being mined from the soil at these N fertilizer levels and that the system would not be sustainable.

Dyadic analyses of friendship in a sample of preschool-age children attending Head Start: correspondence between measures and implications for social competence.

Friendships among a large sample of preschool-age children (N = 471) attending Head Start were assessed. Based on sociometric data, friendship dyads were identified as reciprocated (mutual choice) or nonreciprocated (unilateral choice). Dyads were further classified with respect to gender composition as either same- or mixed-gender dyads. Older children were more likely to participate in a reciprocated friendship than were younger children and reciprocated dyads were more likely to be same-gender than were nonreciprocated dyads. Analyses of interaction between dyad partners revealed that reciprocated friends interacted more frequently across all categories of interaction coded and looked at each other more frequently than did members of nonreciprocated dyads. For the positive interaction subscore, the friendship status effect was modified by a significant interaction with gender composition such that significant effects of friendship status were obtained only for same-gender dyads. Additional analyses indicated that the average social competence level was greater for reciprocated dyads than for nonreciprocated dyads. The findings suggest that reciprocated friendships are meaningful for preschool-age children and may serve as special socialization contexts in which the repertoire of behavior can be exercised and perhaps improved. They also highlight the salience of same-gender friendships in the preschool classroom.

Prostate cancer: perceptions of African-American males.

The purpose of this study was to determine black adult males' knowledge and perceptions of prostate cancer by using the Health Belief Model. The subjects were obtained by randomly approaching males in churches, housing projects, inner-city health clinics, and inner-city shopping centers in seven major Ohio cities. A total of 290 black males responded to the survey (58% usable response rate). The mean age of respondents was 60 years (standard deviation = 13.8). Subjects often did not identify trouble urinating, pain urinating, or blood in the urine as possible signs of prostate cancer. Less than half of the subjects knew at what age one should start to have prostate examinations. Forty percent did not believe they were more likely than most men to develop prostate cancer. Almost 60% did not know black men were more likely than white men to develop prostate cancer, whereas 45% thought that if they had prostate cancer it would kill them, and another 28% were not certain. The vast majority of respondents did not perceive any barriers to having their prostate checked, yet 19% identified cost of the examination as a potential barrier. Approximately 10% to 20% of the respondents were unsure of or did not agree with the benefits of a prostate examination. Analysis of the effects of age, education level, and income levels on the Health Belief Model variables found level of education had the most significant effect followed by level of income.

Voyager 2 at neptune: imaging science results.

Voyager 2 images of Neptune reveal a windy planet characterized by bright clouds of methane ice suspended in an exceptionally clear atmosphere above a lower deck of hydrogen sulfide or ammonia ices. Neptune's atmosphere is dominated by a large anticyclonic storm system that has been named the Great Dark Spot (GDS). About the same size as Earth in extent, the GDS bears both many similarities and some differences to the Great Red Spot of Jupiter. Neptune's zonal wind profile is remarkably similar to that of Uranus. Neptune has three major rings at radii of 42,000, 53,000, and 63,000 kilometers. The outer ring contains three higher density arc-like segments that were apparently responsible for most of the ground-based occultation events observed during the current decade. Like the rings of Uranus, the Neptune rings are composed of very dark material; unlike that of Uranus, the Neptune system is very dusty. Six new regular satellites were found, with dark surfaces and radii ranging from 200 to 25 kilometers. All lie inside the orbit of Triton and the inner four are located within the ring system. Triton is seen to be a differentiated body, with a radius of 1350 kilometers and a density of 2.1 grams per cubic centimeter; it exhibits clear evidence of early episodes of surface melting. A now rigid crust of what is probably water ice is overlain with a brilliant coating of nitrogen frost, slightly darkened and reddened with organic polymer material. Streaks of organic polymer suggest seasonal winds strong enough to move particles of micrometer size or larger, once they become airborne. At least two active plumes were seen, carrying dark material 8 kilometers above the surface before being transported downstream by high level winds. The plumes may be driven by solar heating and the subsequent violent vaporization of subsurface nitrogen.

Autoenucleación / Autoenucleation

Se presenta el caso clínico de autoenucleación unilateral, en un enfermo esquizofrénico, en un brote psicótico agudo. Son frecuentes las mutilaciones bilaterales por cuanto se propone la blefarorrafía del ojo contralateral en forma temporal mientras es dominado el brote psicótico. A los 4 meses de ocurrido el hecho, el otro ojo no mostraba alteraciones campimétricas ni visuales