New track interval radon exposure meters (operating principle and design).

The operating principle of innovative interval radon exposure meters INERAD (types IE-2 and IE-4) is described. The major technical features of the both models have been standardized as much as possible. The exposure meters use the LR-115 type 2 track threshold detector, which is sensitive to alpha particles.

Can scintillation detectors with low spectral resolution accurately determine radionuclides content of building materials?

The current paper makes an attempt to check whether the scintillation NaI(Tl) detectors, in spite of their poor energy resolution, can determine accurately the content of NORM in building materials. The activity concentrations of natural radionuclides were measured using two types of detectors: (a) NaI(Tl) spectrometer equipped with the special software based on the matrix method of least squares, and (b) high-purity germanium spectrometer. Synthetic compositions with activity concentrations varying in a wide range, from 1/5 to 5 times median activity concentrations of the natural radionuclides available in the earth crust and the samples of popular building materials, such as concrete, pumice and gypsum, were tested, while the density of the tested samples changed in a wide range (from 860 up to 2,410 kg/m(3)). The results obtained in the NaI(Tl) system were similar to those obtained with the HPGe spectrometer, mostly within the uncertainty range. This comparison shows that scintillation spectrometers equipped with a special software aimed to compensate for the lower spectral resolution of NaI(Tl) detectors can be successfully used for the radiation control of mass construction products.

Effect of voltage drop within the synaptic cleft on the current and voltage generated at a single synapse.

In a model of a single synapse with a circular contact zone and a single concentric zone containing receptor-gated channels, we studied the dependence of the synaptic current on the synaptic cleft width and on the relative size of the receptor zone. During synaptic excitation, the extracellular current entered the cleft and flowed into the postsynaptic cell through receptor channels distributed homogeneously over the receptor zone. The membrane potential and channel currents were smaller toward the cleft center if compared to the cleft edges. This radial gradient was due to the voltage drop produced by the synaptic current on the cleft resistance. The total synaptic current conducted by the same number of open channels was sensitive to changes in the receptor zone radius and the cleft width. We conclude that synaptic geometry may affect synaptic currents by defining the volume resistor of the cleft. The in-series connection of the resistances of the intracleft medium and the receptor channels plays the role of the synaptic voltage divider. This voltage dividing effect should be taken into account when the conductance of single channels or synaptic contacts is estimated from experimental measurements of voltage-current relationships.