Modeling the impact of uncertainty in detector specification on efficiency values of a HPGe detector using ANGLE software

The objective of this study is to model the impact of uncertainties in the engineering specifications of a typical p-type HPGe detector on the efficiency values when the measured soil sample is in contact geometry with the detector. We introduce a parameter named the normalized sensitivity impact which allows a comparative analysis to be made of the impact of the detector specification uncertainties and develop a correction factor table for the most important parameters. The areas of the detector most susceptible to error were found to be the crystal geometry, vacuum layer above the crystal and the bulletizing radius. In all cases the major impacts were mathematically modeled - for the first time - and found to vary either quadratically or logarithmically over the energy range of 180 keV to 1500 keV. Finally, we propose a set of detector characterization values that may be used in ANGLE for generating a reference efficiency curve using the efficiency transfer method inherent in this software. These values are to be used with the understanding that their uncertainty impact on the full-peak efficiency though not very significant in this counting arrangement, is not non-zero.

Experimental testing of the digital multichannel analyzer for gamma spectrometry measurements

The results of experimental testing of the digital multichannel analyzer which digitalizes the signal after a preamplifier are presented. The recordings of some of the characteristics of the spectrometer containing a digital MCA, such as full-peak efficiency, net area ratio of the two peaks and the stability of the peak position, were carried out under different input counting rates, with different radioactive sources. The tested MCA has shown some excellent features, like the stability of the peak position over a long-term period and flexibility in the adjusting of optimum measurement conditions. However, the performed tests have also shown some serious and unexpected disadvantages of the digital MCA when it operates under certain circumstances, one of them having to do with the automatic tuning of live-time correction at low-input counting rates.

Qualitative phase analysis system for crystalline mixtures based on X-ray powder diffraction file

A qualitative phase identification system for crystalline mixtures is presented. The system provides up to five-phase qualitative identification using up to nine-peak filtration, and additive full peak matching based on the powder diffraction file of ICDD. It was implemented using Microsoft Visual C++, and runs under most common Windows systems. Screenshots and examples are included.

Seasonal Settlement of Polychaetous Annelids on Test Panels in Los Angeles–Long Beach Harbors 1950–1951

Twenty-four species of polychaetes settled on test blocks suspended at 13 stations in Los Angeles–Long Beach harbors in 1950–51. Polydora limicola, Capitella capitata, and Hydroides pacificus were the three most frequently occurring species. Although a peak in settling occurred during the spring months, in general, the warmer the water, the greater the number of species present. However, H. pacificus possessed a summer-full peak, and C. capitata exhibited no apparent peak. Many of the species reproduced throughout the year, as indicated by settlement data. A suppression in the number of species was observed whenever the dissolved oxygen concentration was below 4.0 mg/liter.

SUPPRESSION OF MEMORY BY PASSIVE IMMUNIZATION LATE IN THE PRIMARY RESPONSE

The acquisition of a capacity to respond well to sheep erythrocytes in the presence of anti-SRBC antibody was taken as an indication of the presence of immunological memory. By the use of passive immunization, both the primary IgG plaque-forming cell response and the establishment of memory were abolished, despite occurrence of a full peak IgM PFC response. Evidence for regarding the aquisition of memory and the IgM PFC and IgG PFC responses as three separate processes was presented. Antibody on day 3 of the response to 1.5 x 108 SRBC abolished formation of memory; this effect was less if passive immunization was further delayed and absent by day 10.