Beta spectrum

A special case in Table III is the element phosphorus, which is often of interest in polymers. Its radioactive isotope P-32 emits hic i-energy beta-rays but no gamma-rays. We detect it with a beta spectrometer enplcying a 0.6 cm thick plastic scintillator coupled to a photomultiplier tube. The one gram sanple of polyethylene was too thick for the measurement of the beta-rays due to their lewer penetrability. Thus, for this measurement, a sanple 0.1 cm thick and 2 cm diameter was prepared after irradiation. Analysis of the beta spectrum permits the separation of the P-32 betas from other lewer energy betas. 

The activities of some isotopes, in particular °Sr- °Y, can also be detected by liquid-crystal spectrometry with the use of the Cherenkov phenomenon [10, 11]. The Cherenkov effect is used to determine beta isotopes emitting particles whose iiniax IS above 500 keV [12]. The main advantage of beta activity determination by the Cherenkov effect is the use of analytical preparation used for another chemical analysis (e.g. calculation of recovery). Moreover, the addition of low energy beta or alpha radiation does not disturb the measurement, thereby lowering the cost of analysis. The weakness of this method is the decreased recovery registration and the decline in information about the realistic appearance of the beta spectrum [13]. The determination of beta isotopes in environmental samples is very difficult and requires their chemical isolation. The type of sample and the time of chemical analysis determine the choice of analytical method. Also, the time between contamination and sample collection is important procedures used for samples recently contaminated are different to those used for old samples in which the decay of short-lived radionuclides has aheady taken place [1, 5]. 

Because of the low-energy tail, if one measures a continuous spectrum (e.g., one beta spectrum or a mixture of beta spectra), the measured spectrum will be higher than the source spectrum at the low-energy end and lower at the... 

Pure beta-emitting isotopes exist and may be used for calibration, but only after the energy spectrum is cast into a form called the Kurie plot. The beta spectrum is continuous and extends from zero energy up to a maximum end point kinetic energy (see Fig. 13.12). Because of the shape of the spectrum, it is impossible to accurately determine the end point energy. However, from the... 

The nuclei of mass 39 are analogous to 0 in that single particle (actually hole) levels are expected to occur in Ca. There is no evidence on this point. The decay to appears from the positron spectrum end-point to be governed by the Coulomb energy, and in this case the T =— nucleus is again stable. A also decays, by a forbidden transition, to the 3/g+ ground state of Analysis of the shape of the beta spectrum classifies the transition as Zl/ = 2, yes, so that... 

No levels of the proton-unstable nucleus are known. levels are obtained from the (dp), (den) and (hol) reactions. The beta decay of to the 0 ground state is first forbidden, but transitions to the 7.12 and 6.14 MeV negative parity states are allowed, and the subsequent gamma radiation has been detected. The spin of is therefore probably 2". The isotopic spin allowed transition between the 7.12 and 6.14 MeV levels was not observed and the difference in intensity between the beta-spectrum components and the subsequent radiations is attributed to experimental uncertainties in the measurement of the former. 

In the revised Q system, Qg is calculated by using the complete beta spectra for the radionuclides of ICRP Publication 38 (see Ref. [1.13]). The spectral data for the nuclide of interest are used with data from Refs [1.14,1.15] on the skin dose rate per unit activity of a monoenergetic electron emitter. The self-shielding of the package was taken to be a smooth function of the maximum energy of the beta spectrum (Fig. 1.2). Qg is given by... 

Phosphorous. The presence of trace amounts of phosphorus in metals and semiconductors is known to affect material properties. The produced in the (n,y) reaction is a pure emitter and has to be separated and rigorously purified. Paul (1998,2000) developed a method for P determination in steels and other high-temperature refractory alloys of interest to the aircraft industry. Irradiated samples were dissolved passed through cation-exchange columns to remove Co, Ni, and Cr followed by repeated precipitations of magnesium ammonium phosphate and ammonium phosphomolybdate. One of the major advantages of this technique is the determination of the chemical yield by gravimetry. Phosphorus was determined by INAA in matrices other than metals, e.g., polymers. In this case, the beta spectrum was corrected for interferences and self-absorption (St-Pierre and Kennedy 1998). A modified version of this procedure has been used to certify implanted phosphorus in silicon (Paul et al. 2003). 

Positive-ion electrospray mass spectrum of human hemoglobin (a) as initially obtained with all the measured masses, and (b) after calculation of true mass, as in Figure 8.3. The spectrum transforms into two main peaks representing the main alpha and beta chains of hemoglobin with accurate masses as given. This transformation is fnlly automated. The letters A, B, C refer to the three chains of hemoglobin. Thus, A13 means the alpha chain with 13 protons added. 

Diels-Alder reaction of, 575 electrostatic potential map of, 576 evidence for, 575 structure of, 576 Bergman, Torbern, 2 Bergstrom, Sune K., 1068 Beta anomer, 984 Beta-carotene, structure of, 172 industrial synthesis of, 722 UV spectrum of, 504 Beta-diketone, 851... 

Shiratori Y, Nakata R, Shimizu N, Katada H, Hisamitsu S, Yasuda E, Matsumura M, Narita T, Kawada K, Omata M (2000) High viral eradication with a daily 12-week natural interferon-beta treatment regimen in chronic hepatitis C patients with low viral load. Dig Dis Sci 45 2414-2421 Sidwell RW, Huffman JH, Khare GP, Allen LB, Witkowski JT, Robins RK (1972) Broad-spectrum antiviral activity of Virazole l-beta-D-ribofuranosyl-l,2,4-triazole-3-carboxamide. Science 177 705-706... 

Sidwell RW, Huffman JH, Khare GP, Allen LB, Witkowski JT, Robins RK (1972) Broad-spectrum antiviral activity of Virazole l-beta-D-ribofuranosyl-l,2,4-triazole-3-carboxamide. Science 177(50) 705-706... 

The most obvious feature of the 15N-1H correlation spectrum of A131A is what is missing All of the peaks corresponding to the first 30 residues are absent. In the native structure these residues form a three-strand beta meander which combines with a two-... 

In practical terms, it is invariably a nitrogen atom that is protonated in salt formation. This always leads to a downfield shift for protons on carbons both alpha and beta to the nitrogen concerned. In alkyl amines, the expected shifts would be about 0.7 and 0.3 ppm respectively. Remember that some heterocyclic compounds (e.g., pyridine) contain nitrogen atoms that are basic enough to protonate and comparable downfield shifts can be expected (Spectrum 5.9). 

In the last decade, neutrino experiments have demonstrated that neutrinos are massive particles which may oscillate among three autostates. Such experiments [77-82] have evidenced the mass difference between the autostates, but not the neutrino mass scale value. The only way to determine the neutrino mass is the knowledge of the shape of the end point of energy spectrum in beta decays. In the hypothesis of the Majorana neutrino (neutrino coincides with antineutrino and its rest mass is different from zero), the measure of the decay half-life in the neutrinoless double-beta decay (DBD) would be necessary. A number of recent theoretical interpretations of neutrino oscillation experiments data imply that the effective Majorana mass of the electron neutrino (as measured in neutrinoless DBD) could be in the range 0.01 eV to the present bounds. 

The mass spectrum of dobutamine hydrochloride given in figure 5 shows the molecular ion of the free base at m/e 301. The major fragmentation consists of a cleavage beta to the nitrogen to yield peaks at m/e 123 and 178 with relative intensities, to the base peak, of 15.2 and 97.6%, respectively. The base peak is at m/e 107. 

Ti-beta at 77 K exhibits a photoluminescence spectrum at about 465 nm (95). The excitation was at 260 nm. Addition of H20 and C02 quenches the photoluminescence, H20 being more effective than C02 (Fig. 4). The lifetime of the charge transfer excited state was also shortened by such additions, indicating that H20 and C02 interact with the Ti4+ ions in both the ground and excited states. 

Fig. 4. (a) The photoluminescence spectrum of Ti-beta(OH) and the effects of the addition of C02 ((b) 0.5 mmol CO2/g) and H20 ((c) and (d) 0.1 and 0.5 mmol H20/g, respectively) molecules on the photoluminescence spectrum. Measurements were made at room temperature with excitation at 260 nm [Reproduced from Yamashita et al. (95) with kind permission of Kluwer Academic Publishers]. 

Singh, B.N. (1990) in A Symposium ControlUng Cardiac Arrhythmias with Sotalol, a Broad-Spectrum Antiarrhythmic with Beta-Blocking Effects and Class III Activity (Singh, B.N., ed.). Am. J. Cardiol. 65 No. 2 pp. 3A-11 A. 

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