A new determination equipment combined with the time interval analysis (TIA) has been developed for the simultaneous determination of concomitant alpha–emitting nuclides, such as Pu, Am, Cm and natural alpha–emitters in dust samples. This discrimination technique for the determination of artificial alpha–nuclides is based on the selective subtraction of natural alpha–nuclides contribution to the total pulses by analysing the time interval distributions due to the successive alpha- and beta decay events within millisecond or microsecond orders.
Authors:T. Hashimoto, Y. Uezu, F. Ishizuka, and H. Washio
A selective extraction of the correlated events due to three kinds of short-lived -decay events,216Po (145 ms),217At (32.3 ms) and215Po (1.78 ms), from other random background events were examined by using a time interval analysis (TIA) from the viewpoint of detection sensitivity. In the theoretical treatment based on the probability and statistics, it was clarified that the detection sensitivity proportionally increased with shortening half-lives in the following order,215Po>217At>216Po. In the experiments, pulses from a liquid scintillator owing to -decay events were analyzed using a multiple TIA technique and resulted in the highest sensitivity of219Rn–215Po pairs in the actinium series. Thus, the multiple TIA method was applied to the practical determination of219Rn–215Po pairs in natural samples.
Authors:T. Hashimoto, M. Noguchi, H. Washio, Y. Yamamoto, and Y. Uezu
A delayed coincidence method has been developed for the selective extraction of radionuclides with half-lives of millisecond order using a personal computer. The time interval analysis is fundamentally based on the distinction of the time interval distribution between the correlated and random events, which arise from radioactive disintegration and/or background events within a certain fixed time. Theoretical functions of a time spectrum or a time distribution curve were dealt with from aspects of statistical treatments consisting of a single time interval analysis and a multiple one (STA and MTA). The theoretical equations obtained were used to simulate time spectra on the assumption of some ideal data and compared with the experimental results. Conclusively, the MTA method has been verified to be more suitable for the selective extraction of the objective correlated events from random or background events for the search of radioactive nuclides with millisecond life-times.
Authors:T. Hashimoto, F. Ishizuka, Y. Yoneyama, T. Kubota, and N. Fukuyama
The time files due to radioactive decay events were analyzed for the selective extraction of successive alpha-decay pulse events in millisecond orders, such as216Po (145 ms, thorium series),217At (32.3 ms, neptunium series), and215Po (1.78 ms, actinium series) after respective preceding parents decay, using a multiple time interval analysis (TIA-MTA) technique from both theoretical and experimental viewpoints. In the theoretical treatments, the detection sensitivities of each correlated event in natural decay series was compared with more generalized conditions. It was noteworthy that the evaluated detection sensitivity had increased proportionally with shorter half-lives in the following order:214Po>215Po>217At>216Po.Finally, the present TIA was applied to the clarification of thorium series disequilibrium states in Tamagawa (Akita, Japan) Hot Spring waters. Activities of224Ra were evaluated to be 3.41±0.38 and 0.60±0.08 Bq/l at the upper and lower stream, respectively. The results from activity ratios of radium to thorium isotopes showed a preferential precipitation of radium isotopes in comparison with thorium, reflecting the sensitivity to the lowering acidity of strongly acidic hot spring waters in the lower end of the stream.
Authors:H. Sakaue, H. Fujimaki, S. Tonouchi, S. Itou, and T. Hashimoto
A portable system for high-speed time interval analysis (TIA) method was constructed. The system installed with an original
time counting board could record pulse incident time of 1 MHz precisely. During the measurement, calculation of time intervals
for all the pulses and on-line display of the results were performed simultaneously. Using this system, the correlated decay
events of 214Bi to 210Po in the airborne dust collected on filter paper were counted, together with a dual-phosphor type alpha/beta detector. A
rapidly detective technique of artificial radioactivity under the variations of naturally occurring radioactivities is discussed.
Authors:T. Hashimoto, Y. Yoneyama, K. Sato, and Y. Komatsu
Time interval analysis (TIA), which has been verified to be suitable for the selective extraction of correlated successive
α-decay events within a liquid scintillator, was further developed by combining pulse shape discrimination technique and simple
chemical analysis. A β-emitter nuclide,225Ra, which is suitable for the use as a yield tracer belonging to Np-decay series, was also found to be detectable by the TIA-method
after a certain standing period when the radium-extractant (RADAEX) was added small amounts of HDEHP [di (2-ethylhexyl) phosphoric
acid], which was proved to keep the equilibrium state between Ra and its descendants. The present counting system (TIA analysis
incorporated α-LSC/PSD) has been verified to be applicable to the simultaneous determination of three (including Th, Ac, and
Np) decay series, if the chemical purification of radium fraction was applied to the environmental samples using an extractive
scintillator in addition to utilization of an α-peak itself at lowest energy for the determination of226Ra in uranium decay series. This radioanalytical method was practically applied to the determination of natural radionuclides
belonging to three decay series in environmental samples and compared to the alpha-spectrometric results using a Si-surface
barrier detector (SSB).
Authors:T. Hashimoto, K. Sato, Y. Yoneyama, and N. Fukuyama
Some improvements of the detection sensitivity in pulse time interval analysis (TIA) based on selective extraction of successively - correlated decay events within millisecond order from random or background events, were established by the utilization of PSD, to reject /-pulses from -ones and a simple chemical procedure of radium separation, together with the use of well resolved scintillator. By applying the PSD, the contribution of -decay events was completely eliminated in both the -spectra and the TIA distribution curves as well as the improvement into clear energy resolution and the enhancement of detection sensitivity for the TIA. As a result, the TIA and -spectrometric analysis of226Ra-extract showed the existence of223Ra (Ac-series) and /-correlated events with correlated life (due to 0.16 ms due to214Bi()
214Po()) along with a singly well resolved -peak to be useful for the determination of226Ra (U-series). The difference of half-lives (145 and 1.78 ms) due to216Po and215Po (direct daughters of224Ra for Th-series and223Ra for Ac-series, respectively) was also proven for the possibility of the simultaneous determination of both correlated events by using the TIA/PSD combined with chemical separation and liquid scintillation counting method. Finally, the simultaneous determination of three natural decay series, which include U-, Th- and Ac-series nuclides, have been conveniently carried out for some environmental samples using the present method combined with225Ra yield tracer (Np-series).
Hungarian has a number of apparently synonymous time adverbs that can measure the duration of time intervals. The paper explores these adverbs in some detail, and argues that contrary to appearances, none ofthem are freely interchangeable. The starting point is a discussion of the property of homogeneity that time adverbs are sensitive to. The paper argues for a specific treatment of homogeneity and a preliminary adverb definition based on that treatment. It is proposed that some, but not all, Hungarian time adverbs share the default definition. The diverging adverbs may (a) contain a covert frequency predicate or (b) not measure the duration of the time interval directly, but by determining an endpoint of the interval. Hungarian time adverbs also differ in the range of time intervals they can measure; some, but not all adverbs can measure all available time intervals including the event, iterative, habitual and reference time. This variability in time adverb modification is arbitrary and needs to be explicitly determined for each adverb. Apart from discerning the interpretation of Hungarian time adverbs, the conclusions have a more general impact. On the one hand, apparently homogeneous adverbs can have disparate definitions. On the other, it is necessary to permit explicit, arbitrary constraints on adverbial modification. It is also argued that time adverbs can impose non-local restrictions on the eventuality modified, strengthening the need for a powerful theory of adverbial modification.
Some details of an earlier described method are dealt with. The procedure can be based on observing the fate of only selected
(e.g. n-th) events in the acquisition chain. Non-observable pile-up can be accounted for by extrapolation. A survey of the
related circuitry including the timer control is given.
The goal of the present study was to find out the best interval after hCG injection in PMSG primed prepuberal gilts for retrieval of in vivo matured oocytes for in vitro fertilisation (IVF). Altogether 66 gilts were superovulated with 1500IU PMSG and 500IU hCG 72h later. Ovum pick up was performed endoscopically 24, 28, 32 or 36h after hCG and a total of 869 cumulus-oocyte-complexes (COCs) were aspirated from 1400 follicles. COCs were tested for quality, and an aliquot was immediately fixed and stained to determine meiotic configuration. The remaining COCs were fertilised in vitro using frozen-thawed epididymal semen. Quality and developmental stage of embryos were tested after IVF, and the number of nuclei was counted. At 24 to 32h after hCG only few oocytes have entered the second meiotic cycle (18 to 25% vs. 58% at 36h, p<0.05). The overall cleavage rate was significantly influenced by insufficient maturation rate at the early collection times (14% at 24h vs. 49% at 36h). Additionally, when oocytes were collected 24 to 32h vs. 36h the cleavage rate based on mature oocytes was lower (26 vs. 62%, p<0.05). Once embryonic development has been initiated, the further in vitro development to blastocyst stages did not differ between groups. However, the number of cells was lower at collection times 24 to 32h as compared to 36h after hCG (12 to 15 cells vs. 22 cells, p<0.05). The results indicate that the time of COC collection affects the in vitro developmental competence up to the blastocyst stage and should not be performed earlier than 36h after hCG treatment.