Effects of perinatal testosterone on handedness of gerbils: Support for part of the Geschwind-Galaburda hypothesis.

When assuming their species-typical tripodal stance. male Mongolian gerbils (Meriones unguiculatus) use their right forepaw for support more frequently than do females. This experiment determined whether. as N. Geschwind and A. M. Galaburda (1987) have proposed, the direction of such sexualIy dimorphic lateral asymmetry of forelimb use is affected by perinatal exposure to testosterone (TP). It was found that male gerbils injected with TP when 4 days old were significantly less likely to rest on their right forepaw when in a tripodal stance than were their oil-injected siblings. Female gerbils injected with TP when 6 days old were more likely than oil-injected controls to use their right forepaws for support. The findings demonstrate effects of perinatal exposure to TP on handedness in gerbils and suggest that the relationship between TP exposure and asymmetrical forelimb use is not always as direct as Geschwind and Galaburda's model suggests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An IFYGL Carbon Budget for Lake Ontario

A carbon budget was produced for each month of the International Field Year for the Great Lakes (IFYGL) year (April 1972 to March 1973) to determine the importance of the various sources and sinks of carbon. Major sources were found to be CO₂ which was fixed in organic matter during primary production and inorganic carbon in tributary streams, especially the Niagara River. The major sinks were found to be inorganic carbon outflow at the St. Lawrence River and net CO₂ gas exchange between the inorganic carbon pool and the atmosphere. Inflow and outflow of organic matter in rivers, sedimentation of organic and inorganic matter, ground water transport, and municipal and industrial perturbations accounted in total for less than 10% of the annual budget.The lake had an inventory of approximately 4.0 × 10¹⁰ kg of inorganic carbon and approximately an order of magnitude less organic carbon. The riverborne flux of inorganic carbon of 0.5 × 10¹⁰ was 13% of the lake's inventory, assuming complete mixing; a minimum mean residence time of 8 years can be calculated from that inventory.The seasonal cycle inherent in the fixation of carbon in primary production was primarily balanced by a complementary seasonal cycle in the air-lake CO₂ gas exchange system. The lake acts as a sink for CO₂ gas in the warm months when primary productivity is highest and as a source of CO₂ in the colder part of the year.The IFYGL year had higher than normal rates of water flow, but this does not appear to have perturbed the inorganic carbon system. A comparison of IFYGL carbon budget results with corresponding estimates calculated for a typical year from historical data shows no major differences.     

Thermal effects on the forward characteristics of silicon p-i-n diodes at high pulse currents

When applying high pulse currents, the resulting temperature increase in the base regions of p-i-n diodes and thyristors leads to notable changes in the forward characteristics. (I) Decrease of carrier mobility noticeably increases the voltage drop across the diode and tends to limit the current density. (II) When the temperatures are sufficiently high to supply high intrinsic carrier concentrations, the temperature coefficient of the resistivity becomes negative. This can lead to current localization and destruction of the diodes.

To study these effects, the temperature of the base regions was monitored during high pulse currents using thermal i.r. emission. Indication for current limit occurs above 200°C, when the diodes are heated from room temperature. The negative temperature coefficient of the resistivity occurs at temperatures at which the intrinsic carrier concentration has reached the same order of magnitude as the injected carrier density. Simple theoretical treatment yields reasonably good agreement with the experimental results.     

Effects of changes in the atmosphere on solar insolation

A review of the nature of solar radiation and the spectral distribution of its energy is presented. The attenuation of solar radiation by scattering and absorption and the effects of atmospheric pollutants on radiation attenuation with an estimate of the long-term effects of pollutants is discussed.