No abstract

Human infants (1-3 days of age) were offered water and a solution of glucose, fructose, lactose, or sucrose for 3-min. periods. Volumes ingested were measured. Infants discriminated between water and a solution of sugar, demonstrating a distinct preference for the latter. The effectiveness of sugars in evoking ingestion varied with both the compound and the solution concentration.Human infants have a greater number and wider distribution of taste buds in the oropharynx than do adults (Arey, Tremaine, & Monzingo, 1935). Several studies indicate that these receptors are functional at birth. However these investigations are inconclusive and sometimes contradictory, particularly in denning the influence of chemical stimuli on ingestion. For example, Jensen (1932) measured sucking responses of infants to 10-sec. presentations of water, acid, milk, and a .33 M glucose solution. He did not find differences in the responses to these fluids. delivered a milk formula or a .28 M glucose solution on a partial reinforcement schedule for 2-min. sessions. They found that infants differentiated between the fluids in sucking time and frequency but not in sucking rate or pressure. In a similar study, however, Kron, Stein, Goddard, and

The south-eastern United States and Gulf Coast of Mexico is physiographically diverse, although dominated by a broad coastal plain. Much of the region has a humid, warm temperate climate with little seasonality in precipitation but strong seasonality in runo owing to high rates of summer evapotranspiration. The climate of southern Florida and eastern Mexico is subtropical with a distinct summer wet season and winter dry season. Regional climate models suggest that climate change resulting from a doubling of the pre-industrial levels of atmospheric CO 2 may increase annual air temperatures by 3±48C. Changes in precipitation are highly uncertain, but the most probable scenario shows higher levels over all but the northern, interior portions of the region, with increases primarily occurring in summer and occurring as more intense or clustered storms. Despite the increases in precipitation, runo is likely to decline over much of the region owing to increases in evapotranspiration exceeding increases in precipitation. Only in Florida and the Gulf Coast areas of the US and Mexico are precipitation increases likely to exceed evapotranspiration increases, producing an increase in runo. However, increases in storm intensity and clustering are likely to result in more extreme hydrographs, with larger peaks in¯ow but lower base¯ows and longer periods of drought.The ecological eects of climate change on freshwaters of the region include: (1) a general increase in rates of primary production, organic matter decomposition and nutrient cycling as a result of higher temperatures and longer growing seasons: (2) reduction in habitat for cool water species, particularly ®sh and macroinvertebrates in Appalachian streams; (3) reduction in water quality and in suitable habitat in summer owing to lower base¯ows and intensi®cation of the temperature±dissolved oxygen squeeze in many rivers and reservoirs; (4) reduction in organic matter storage and loss of organisms during more intense¯ushing events in some streams and wetlands; (5) shorter periods of inundation of riparian wetlands and greater drying of wetland soils, particularly in northern and inland areas; (6) expansion of subtropical species northwards, including several non-native nuisance species currently con®ned to southern Florida; (7) expansion of wetlands in Florida and coastal Mexico, but increase in eutrophication of Florida lakes as a result of greater runo from urban and agricultural areas; and (8) changes in the¯ushing rate of estuaries that would alter their salinity regimes, strati®cation and water quality as well as in¯uence productivity in the Gulf of Mexico.Many of the expected climate change eects will exacerbate current anthropogenic stresses on the region's freshwater systems, including increasing demands for water, increasing waste heat loadings and land use changes that alter the quantity and quality of runo to streams and reservoirs. Research is needed especially in several critical areas: long-term monitoring of key hydrological, chemical and biologi...

Computational simulations offer a powerful tool for quantitatively investigating radiation interactions with biological tissue and can help bridge the gap between physics, chemistry and biology. The TOPAS collaboration is tackling this challenge by extending the current Monte Carlo tool to allow for sub-cellular in silico simulations in a new extension, TOPAS-nBio. TOPAS wraps and extends the Geant4 Monte Carlo simulation toolkit and the new extension allows the modeling of particles down to vibrational energies (~ 2 eV) within realistic biological geometries. Here we present a validation of biological geometries available in TOPAS-nBio, by comparing our results to two previously published studies. We compare the prediction of strand breaks in a simple linear DNA strand from TOPAS-nBio to a published Monte Carlo track structure simulation study. While TOPAS-nBio confirms the trend in strand break generation, it predicts a higher frequency of events below an energy of 17.5 eV compared to the alternative Monte Carlo track structure study. This is due to differences in the physics models used by each code. We also compare the experimental measurement of strand breaks from incident protons in DNA plasmids to TOPAS-nBio simulations. Our results show good agreement of single and double strand breaks predicting a similar increase in the strand break yield with increasing LET.