Source counts

The IRAS galaxies provided some of the earliest evidence from redshift surveys, and from source counts as a function of observed flux, that the spiral galaxy population has undergone evolution (ORS see Fig. 12.2). This result is analogous to similar evidence from source counts of radio galaxies and quasars, as well as quasar redshifts, and a correlation that has been observed between radio and infrared luminosity suggests that the evolution could be similar in both cases. Typical simple models for such evolution include luminosity evolution according to... 

Fig. 12.2. IRAS differential source counts as a function of observed flux at 60 xm, normalized to a uniform population in Euclidean space. After Oliver, Rowan-Robinson and Saunders (1992).

Ref. Material Source Counts Organisms commonly found... 

Step 2. Measure the control source count rate of each peak and compare it to the routinely recorded counting room QA information on these source-peak count rates. 

Seven portions of natural uranium as the oxide UgOg were irradiated, processed chemically after the addition of barium carrier, and the barium sulfate sources counted for 4 min (approximately 50,(KK) counts). The coefficient of variation on a single result was found to be 0.53% of which 0.44% was due to statistical variations in the count rate. 

No = geometric mean of flood source count rate with regions defined from the transmission scan... 

Fitting to Scatter Outside the Object In this method, the scatter is estimated by fitting an analytic function (Gaussian or parabolic) to the activity outside the source and interpolating the function to the source. The interpolated scatter contributions are then subtracted from the measured source counts to obtain scatter-corrected data for reconstruction of PET images. This method is based on the assumption that (1) the events outside the source are only scatter events, (2) the scatter distribution is a low-frequency function across the FOV, and (3) they are independent of activity distribution in the source. 

Figure 8.1 A point isotropic source counted by a pulse-type counting system.

Instead of the above-cited control chart to test the hypothesis that the measured values are randomly distributed, a tolerance chart may be established to compare periodic measurements with established acceptance limits (see ANSI N42.2, Appendix A). In this system, an acceptable relative standard deviation—say 2% for the standard source count and 10% for background count— is selected and horizontal lines that represent these values are drawn as upper and lower acceptance limits. These limits should be wider than the statistically based limits if they were narrower, they would be exceeded frequently. They need not be symmetrical on the positive and negative side. Their purpose is to keep the counting efficiency and background count rate within limits that give acceptable results even if the instrument and its output are subject to nonrandom fluctuations. 

Figure 7.12 Empirical correction for variable height of a cylindrical source counted on the detector cap. The area enclosed by the horizontal dashed lines indicates one standard deviation of the corrected results...

The point sonrce is then measnred at the same distance from the detector as it was when positioned on the sample. The peak area, Rg, is the point source count rate sans sample. (The arrangement shown in... 

The number of tests conducted varies by source. Cochran et al. (1989), states there were 467 explosions Stevenson (2004 27) notes there were 607 nuclear devices. Boztayev (1998), who was mayor of Semipalatinsk, reported there were 509 and one additional blast in 1995. Bulatov (1996) identified 470 explosions. See Skholnik (2002) for a discussion of these issues and also Werner and Purvis-Roberts (2007 296). Some sources counted the number of explosions, while others only the number of tests. According to the Ministry of Atomic Energy and the Ministry of Defense of Russia there were 463 explosions plus 1 in 1995 test (an exploded ordinance) (Boztayev (1998 16-42). I used this source as it listed the number of a test, the date, and the kilotons. 

The differential K luminosity function for the total number of sources found in NGC1333-S shows a rising source count to 14th magnitude beyond whidi, the source count decreases to zero at 17 (due to our limiting E magnitude). 

All photometry was performed with the PHOT routine in IRAF. A 5" aperture centered on the local intensity pesdc was used to determine the source counts, and the sky was sampled in surrounding annuli. The K values for H2B, H5E, and H5W, are influenced by extended emission which is much more evident at longer wavelengths. 

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