Absolute counting

Assay of Radioactive Compounds. The radioactive samples were counted on steel planchets in a Nuclear Chicago Model D-47 low-background gas-flow counting chamber with an absolute counting efficiency (estimated by comparison with a standard) of about 20%. 

The success of antiretroviral therapy is measured by the degree to which the therapy (1) restores and preserves immunologic function, (2) maximally and durably suppresses HIV RNA, (3) improves quality of life, and (4) reduces HIV-related morbidity and mortality. The major outcome parameters are CD4+ lymphocyte absolute count and percentage, and plasma HIV RNA. Adequate immunologic response in antiretroviral-naive patients consists of an increase in CD4+ cell count that averages 100 to 150 cells/mm3 per year (with a faster response in the first 3 months), and a 1 log decrease in HIV RNA by 2 to 8 weeks after starting... 

Hulstaert, F., et al. Age-related changes in human blood lymphocyte subpopulations. II. Varying kinetics of percentage and absolute count measurements, Clin. Immunol. Immu-nopathol., 70, 152, 1994. 

The dilution factor can be automatically computed to give absolute counts for liquids as dense as sludge. Supercount is also loaded with a special program for hydraulic fluids and phi classification. 

Neumann W. and Huster E. (1976) Discussion of Rb-87 half-life determined by absolute counting. Earth Planet. Sci. Lett. 33(2), 277-288. 

Figure 8. Distributions of short-time averaged kinetic energies at various energies for Arij cluster-Here kinetic energy is presented in units of erg/atom instead of temperature units. The corresponding mean temperatures can be easily obtained from the caloric curve of Fig. 7. Solid curves—least-square fits of the points to the sum of two Gaussian curves, (a) In rigid limit portion of caloric curve, E = —4.72 x 10" erg/atoms. (ft) In interval < < at = —4.04 x 10 erg/atom. (c) In coexistence interval at = —3.88 x lO" erg/atom. (d) In nonrigid limit portion of caloric curve, = —3.61 x lO" erg/atom. Vertical scale is in absolute counts for a given run.

Figure 15-1 Toxicogenomics literature has shown a rapid increase over the last decade. PubMed (http //www.ncbi.nlm.nih.gov) literature number was surveyed per year over the past decade using the key term "toxicogenomics and "toxicology," respectively. The number from "toxicology" is divided by a factor of 50 to be normalized with that of "toxicogenomics" as the absolute count for "toxicology" paper is still bigger.

On day 18, blood was taken from saMne-, OVA- and OVA plus Systemic (Sy) HP-NAP-treated animals. Blood smears were stained to calculate the proportions and the mean ( SE) absolute counts of lymphocytes, neutrophils, and eosinophils. Levels of total serum IgE were assessed by a specific ELISA assay. p < 0.01, P < 0.03 OVA plus Sy HP-NAP versus OVA alone. 

Fig. 4 Intraperitoneal administration of HP-NAP inhibited the development of airway eosinophiUa in OVA-sensitized animals, (a) On day 1, mice were sensitized with OVA alone or with OVA plus systemic HP-NAP (Sy HP-NAP), and then exposed to aerosolized OVA. Control animals were injected with PBS alone and then exposed to aerosolized PBS. Cytocentiifuge preparations from BAL of the three groups of animals on day 18 were stained to calculate the proportions of eosinophils, macrophages, neutrophils and lymphocytes. Absolute counts ( SE) for each cell type were calculated from the number of total cells in the BAL. P < 0.01 versus OVA-treated mice, (b) Frozen sections of lungs from OVA-sensitized (left), and Sy HP-NAP-treated OVA-sensitized animals (right). Eosinophil infiltration in the lung is virtually absent in OVA-sensitized mice treated with Sy HP-NAP...

Wh only a single detector in a conventional counting set-up is available (e.g. detector arrangemmit in Fig. 8.4), absolute counting rates can be obtained for unknown samples by conq>arison with known standards. 

Radionuclides that are used as comparison sources, e.g., for determining instrument count rate stability and as tracers, must be of sufficient radiochemical purity and activity to eliminate interference in counting and permit correction for decay, but in most instances they need not have an accurately known disintegration rate. The absolute count rate also is unimportant for energy calibration because only the energy must be accurately known. 

CountBright absolute counting beads (Life technologies. Cat. No. C36950)... 

To count the cells, the cell solution needs to be spiked with a known number of beads—for us, 2000 beads. CountBright absolute counting beads contain 5x10" beads in 50 pi. 

The difficulties in assessing the absolute counting efficiency of heterogeneous samples are outweighed by the convenience of this method of counting unknowns and by the availability of a myriad of commercial mixtures of nonionic and anionic surfactants "designed" for LSC. We have therefore retreated to an attempt to emphasize some of the less obvious pit-falls in such systems. 

When some commercial surfactants exhibited a precipitous drop in and efficiency between 0.5 and 5% water content, as did the nonionic surfactants Triton X-100 or Triton N-101, others behaved in a manner similar to our contrived nonionic-anionic surfactant mixtures. It is thus apparent that accurate calculation of the relative radioactivity of emulsified aqueous samples depends on rigorous uniformity of sample preparations. Optimal proportions of surfactants, surfactant content, and water content will depend on the nature and amount of the solute being counted. The usual methods of quench correction in LSC must be examined very carefully, inasmuch as they will usually not be adequate for determining absolute counting efficiency. 

If absolute counting must be attempted, corrections are necessary for end effects (electric field distortion at the tube extremities) and for wal) effects depending on the specific ionization of the radiation in the counter filling and the minimum number of ion pairs required for detection. Counters may be... 

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