Low Radiation Environment Research Articles

Radiation biophysics at the Gran Sasso laboratory: influence of a low background radiation environment on the adpative response of living cells

Mammalian cells were cultured in parallel at the Istituto Superiore di Sanita', in the presence of standard radiation background, and at the INFN-Gran Sasso underground Laboratory, exposed to low radiation background. Both cultures were grown for up to six months and periodically tested to check for the onset of metabolic changes and different sensitivity to genotoxic damage caused by ionizing and UV radiation, as well as by chemical agents. These tests include measurements of enzyme activities protecting from oxidative cell damage, induction of apoptosis and mutation.

Workshop summary

An attempt is made to summarise the contributions to the VERTEX’97 Workshop. Many detailed presentations were given, so only the highlights (from my point of view) will be presented. Vertex detectors are now at a transition point between their successful application in rather low-radiation environments and the severe tests that await them in future detectors. The contributions cover vertex detectors at various stages in this development.

Physiological characteristics of high-yielding rice inferred from cross-location experiments

Understanding the processes controlling yield in well-managed, high-input crops may offer ways of increasing currently recognized yield potentials. In this study, 13 crops of Koshihikari rice were managed with different nitrogen strategies to achieve maximum yield in three environments, Kyoto (6 t ha −1) and Ina (10 t ha −1) in Japan, and Yanco (13 t ha −1) in Australia. A common set of data on radiation interception, growth, yield, yield components, N uptake and non-structural carbohydrates was collected for each crop. There was a similar efficiency of dry matter production per unit of incident global radiation at the three sites, 0.78 g MJ −1. At Yanco, incident and intercepted radiation were high but were offset by a low conversion of intercepted radiation to dry matter (radiation-conversion efficiency, RCE) of 1.0 g MJ −1 compared to RCE = 1.4 at Kyoto and Ina. The RCE at Yanco was particularly low during the grain filling stage, apparently due to poor root function associated with low soil aeration and to low tiller survival and low minimum temperatures. If these constraints could be overcome and the RCE increased to the values in Kyoto and Ina, the estimated yield potential at Yanco would be about 18 t ha −1. Given the relatively high values of RCE at Kyoto and Ina, the most promising way to increase yield potential would be to increase the efficiency of converting growth to grain yield. At all three locations the number of grains was less than the number of spikelets. The quantity of assimilate available for grain production was estimated from the amount of non-structural carbohydrate at heading plus the dry matter growth after heading. The potential sink for assimilate was estimated from the number of florets and the weight of a filled kernel. By comparing these amounts it appeared that some of the crops at Ina were source limited and some were sink limited, while at Kyoto crops were neither clearly source limited nor sink limited. This paradoxical result is explained by a lack of assimilates soon after heading, leading to poor grain set, followed by a surplus of assimilates during late grain filling. On the basis of other evidence, there appears to be genetic variability for the ability to set grains in conditions of poor assimilate supply, suggesting that in the low-radiation environments in which much rice is grown, there may be scope for increasing yield by increasing the number of fertile florets.

Validation and adjustment of the mathematical prediction model for human sweat rate responses to outdoor environmental conditions.

Under outdoor conditions this model was over estimating sweat loss response in shaded (low solar radiation) environments, and underestimating the response when solar radiation was high (open field areas). The present study was conducted in order to adjust the model to be applicable under outdoor environmental conditions. Four groups of fit acclimated subjects participated in the study. They were exposed to three climatic conditions (30 degrees, 65% rh; 31 degrees C, 40% rh; and 40 degrees C, 20% rh) and three levels of metabolic rate (100, 300 and 450 W) in shaded and sunny areas while wearing shorts, cotton fatigues (BDUs) or protective garments. The original predictive equation for sweat loss was adjusted for the outdoor conditions by evaluating separately the radiative heat exchange, short-wave absorption in the body and long-wave emission from the body to the atmosphere and integrating them in the required evaporation component (Ereq) of the model, as follows: Hr = 1.5SL0.6/I(T) (watt) H1 = 0.047Me.th/I(T) (watt), where SL is solar radiation (W.m-2), Me.th is the Stephan Boltzman constant, and I(T) is the effective clothing insulation coefficient. This adjustment revealed a high correlation between the measured and expected values of sweat loss (r = 0.99, p < 0.0001).

Fast shutter for low background radiation environments at SPR III

A fast shutter system has been developed to isolate experiments from the radiation emitted after the main pulse of the Sandia Pulsed Reactor, SPR III. In about 15 ms the system moves a 20 kg shield in front of the beam port aperture in the facility shield wall. A second gravity-driven shutter is dropped into place in about 200 ms. The total attenuation achieved in the delayed beam intensity is about a factor of one hundred. The shutter assembly was used, along with a sensitive detection system, to observe the gamma ray flux emitted by various materials activated by the neutron beam at levels nine orders of magnitude smaller than the gamma dose rate at the target during the reactor pulse.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Further Measurements on Electrolytic Cold Fusion with D2O and Palladium at Gran Sasso Laboratory

This paper reports on several experiments performed at the Gran Sasso Laboratory on an 0.8-cm-diam {times} 5-cm-long, hyperpure, high-temperature vacuum-annealed palladium rod used as a cathode for electrolytic infusion of D{sub 2}O and 0.1 M LiOH with regular additions of gaseous CO{sub 2} at a current density of 60 mA/cm{sup 2}. In the very low background radiation environment, several gamma bursts lasting up to 15 min were detected whose intensity, in terms of cold fusion, was {gt}10{sup {minus} 20} fusion/(deuteron pair {center dot} s). Under normal background conditions, none of these burst signals would have been detected with statistical significance. The shape and intensity of these signals are quite similar to those detected previously.

The influence of rainfall distribution in numerical simulation of evapotranspiration from a multilayer model pine canopy

A multilayer canopy model is used to simulate the water balance of a pine forest. The role of advected energy in sustaining evapotranspiration from tall canopies in low‐radiation environments is reproduced. The surface water balance of temperate forested areas is not necessarily dominated by evapotranspiration in conditions of high radiation receipt. Interception loss is greater where the rainfall regime consists of shorter events, since long‐duration storms tend to fully saturate the canopy. The achievement of the potential evaporation rate and the onset of drainage then combine to limit interception loss totals. This result is important in considering the possible effect of climatic change on water resources. Catchment yield may be as sensitive to the temporal distribution of rainfall as to seasonal or annual totals.

Are Uranus' rings black because they are in the solar wind?

We show that, for a reasonable range of choices of ionospheric parameters for Uranus and of solar wind parameters at Uranus orbit, the rings of Uranus are for the most part immersed in the solar wind if Uranus lacks an intrinsic magnetic field. If Uranus ionosphere forms the obstacle to the solar wind, then very low upper bounds (1–4 nT) may be obtained for an intrinisic magnetic field at the polar 1 bar level. In addition, from an examination of the geometric albedos of Jupiter's and of Saturn's rings and moons, we show that these bodies have characteristically either high albedos in a low radiation environment or low albedos in a high radiation environment. The only exceptions to this pattern are geologically active moons such as Io. We suggest that the moons of Uranus possess a significantly lower albedo than those in the low radiation environment of Saturn and that the rings of Uranus are black because the rings and moons of Uranus may be relatively depleted in their surface stores of ices. In this scenario, immersion of the rings of Uranus in the solar wind would provide a loss mechanism for ring ices and produce the black rings observed. The black rings of Uranus may thus imply the lack of an intrinsic Uranus magnetic field.