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Early prediction of the prevalence of influenza reduces its impact. Various studies have been conducted to predict the number of influenza-infected people. However, these studies are not highly accurate especially in the distant future such as over one month. To deal with this problem, we investigate the sequence to sequence (Seq2Seq) with attention model using Google Trends data to assess and predict the number of influenza-infected people over the course of multiple weeks. Google Trends data help to compensate the dark figures including the statistics and improve the prediction accuracy. We demonstrate that the attention mechanism is highly effective to improve prediction accuracy and achieves state-of-the art results, with a Pearson correlation and root-mean-square error of 0.996 and 0.67, respectively. However, the prediction accuracy of the peak of influenza epidemic is not sufficient, and further investigation is needed to overcome this problem., 7 pages, ICCBB2019

The increase of positronium formation probability with the time of exposure to positron radiation, observed until now mainly in polymers, is shown for the case of polycrystalline n-nonadecane. Sample illumination by visible light restores the initial low value of positronium intensity owing to elimination of trapped electrons. Slowing down the growth of positronium intensity with prolonged positron irradiation is ascribed to inhibiting action of radicals.

A pulsed slow-positron beam using 22 Na as the positron source has been constructed for characterizing thin polymer films, coating polymer materials and their interfaces. The construction is very simple and the time resolution achieved is about 500 ps, which is sufficient for measuring long-lived positron lifetime components in thin polymer films. The positron lifetime in a 45 nm thick epoxy resin thin film held on a single-crystal silicon substrate has been measured using this pulsed slow-positron beam. Formation of o-positronium (ortho-Ps) is not observed when the incident positron energy is more than about 1 keV. The surface effect of the glass-transition temperature of a 0.3 mm thick polystyrene (PS) film has been also studied. It has been found that the glass-transition temperature of the sub-surface region of PS is lower than that of the PS bulk.

A pulsed slow-positron beam has been constructed for applications to polymer films. A new setup of the moderator system and a new design for the bunching signal waveform are introduced. The results show that such a kind of moderator appears to be good one, and that a new waveform for the bunching is very practical. The current pulsed slow-positron beam can be used to characterize polymer films or porous thin films.

The high-resolution Doppler-broadening spectroscopy of positron-annihilation gamma rays emitted during an experiment on positron annihilation lifetime spectroscopy (PALS) has been applied to study the radiation and oxygen effects on positronium (Ps) formation in polyethylene (PE). Using two Ge detectors, the DB spectra were obtained by measuring the coincidences of two photons. While the Ps formation rate decreased with elapsed time during the PALS experiment, the increase of annihilation on oxygen-containing groups was monitored by coincidence Doppler-broadening spectroscopy (CDBS). This suggested that the decrease in Ps formation was associated with the carbonyl groups (–CO) formed by radiation emitted from the positron sources.

Positron annihilation in hypercrosslinked polystyrene named CPS(0.3)150E has been studied as a function of temperature in the range from 35 to 370 K. The positron lifetime spectra were resolved into five components using the PATFIT program and the MELT programs. The annihilation rate of the longest-lived component was found to increase linearly with increasing temperature. Remarkably, the components of the distributions of the o -Ps lifetimes resolved by MELT demonstrated essential broadening with decreasing temperature.

Positron annihilation lifetime spectroscopy has been applied to low-density polyethylene (LDPE) as a function of the temperature and also the elapsed time in the dark as well as in the light. Positronium formation below, around and above the glass transition temperature of LDPE was investigated. It was found that far below the glass transition temperature, Tg, the o-Ps intensity increased with the elapsed time in the dark. It was interesting to observe an initial rapid increase in the o-Ps intensity, followed by a continuous decrease with the elapsed time, especially at around Tg. Above Tg, the o-Ps intensity decreased very slowly with the elapsed time at 250 K and almost did not decrease at room temperature. Furthermore, no increase, but only a decrease, in the o-Ps intensity with the elapsed time was seen in light. Possible explanations of these effects were discussed. A simple calculation of the activation energy of the trapped electrons was suggested.

Using two Ge detectors, the high-resolution Doppler-broadening energy spectra of positron annihilation gamma rays has been obtained by measuring the coincidences of the two photons. Light bleaching and oxygen effects on positron annihilation were investigated in this way. A large enhancement of the high-momentum part of the coincidence Doppler spectra was observed in poly(methylmethacrylate) (PMMA), which contains oxygen atoms in the polymer structure. Bleaching experiments in PMMA and in copolymer ethylene-methylmethacrylate EMMA (LDPE+MMA 3 mol%) have demonstrated that the enhancement effect may be due to the trapping of positrons by the polar C + O − groups, followed by positron annihilation with the electrons belonging to oxygen.

Positron annihilation in hypercrosslinked polystyrene, called CPS(0.3)150E, has been studied as a function of temperature in the range from 35 to 370 K. The positron lifetime spectra were resolved into five components using the PATFIT and MELT programs. The annihilation rate constant of the longest-lived component was found to increase linearly with increasing temperature. Remarkably, the distribution of o-Ps lifetimes resolved by MELT was shown to broaden with decreasing temperature. Moreover, an effect of the oxygen pressure on the positronium characteristics was also investigated in another hypercrosslinked polystyrene, CPS(0.3)100E. The oxygen pressure varied from vacuum to 6 atm. The annihilation rate constants of the long-lived components were observed to increase linearly as a function of the oxygen pressure, which demonstrates a dependence of the kinetic of o-Ps quenching on the pore size.

Positron annihilation lifetime spectroscopy (PALS) was applied to low-density polyethylene (LDPE) and ethylene-methylmethacrylate (EMMA) copolymers with various MMA contents. The experiments were conducted in the dark as well as under visible light condition. In the dark at a low temperature of about 30 K, the o-Ps intensity was observed to increase with the elapsed time, and the increasing rate depended on the MMA content. After being kept for a long time at low temperature, the sample temperature was increased. The o-Ps intensity and its lifetime were found to change as a function of temperature. In the light, no significant change was found for the o-Ps intensity below the glass transition temperature. However, a dramatic variation of the o-Ps intensity was found to correspond to a change of its lifetime in the dark. The observations showed that not only the variation of the o-Ps lifetime could be related to the structural change and molecular motions of polymers, but also the change of the o-Ps intensity, particularly at low temperature in the dark, could be related to the activation of molecular motions. The results indicated that PALS could be used as a novel probe for molecular motions at low temperature.

Possibility of a real-time tritium monitoring in high-energy accelerator facilities is examined using a polyimide hollow-filament type membrane module. Enrichment characteristics of hydrogen isotop...

During positron annihilation lifetime spectroscopy (PALS) experiments of polymers, positrons emitted from the positron source induce radiation effects in the sample. Since these radiation effects can affect positronium (Ps) formation probability, PALS has some potential to be used as a new tool to study radiation effects. As a function of the contact time of the sample with the positron source, the Ps formation probability increases or decreases at low temperature or at room temperature, respectively. The decrease of the Ps formation probability at room temperature may be attributed to the accumulation of free radicals that can scavenge the electrons which could otherwise have combined with positron to form Ps. The increase at low temperatures may be attributed to the accumulation of trapped electrons that can be picked up by positrons to form Ps.

In solid crystalline biphenyl, ortho -positronium ( o -Ps), abundant at normal pressure, can be eliminated by application of a pressure of about 100 MPa. The lifetime of o -Ps shortens with the rise of pressure, as a result of diminishing of the free spaces in which it is trapped. However, the lifetime of para -Ps seems to increase, and at 80 MPa, it cannot be distinguished from that of free positrons. Another new effect is the reappearance of the long-lived component in the positron lifetime spectrum at high pressures. The same effect of positronium reappearance, although not so well pronounced, was found in biphenyl at low temperatures.

現在,各国において種々の大強度高エネルギー加速器施設の建設計画が進められており,加速器を利用して得られる様々な放射線を用いた研究が,今後ますます盛んになることが予想される。大型加速器施設では,加速器の運転に伴い発生する高エネルギー放射線と,それにより生成される放射化物などに対する安全対策が重要になるが,原子炉施設とは異なる加速器施設特有の問題もある。本稿では,その一つである高エネルギー加速器施設における放射化と,それに基づく内部被ばくの問題について,加速器施設の安全管理の経験から得られた知見を中心に紹介する。

The irradiation effect of γ-rays on polypropylene (PP) has been studied through relaxational behaviour, using the positron annihilation lifetime (PAL) method. At low temperature, the intensity of a long-lived component of positronium, I3, for unirradiated PP samples increased due to a termination of the local thermal motion of polymer structures. At 100 K, the increase in I3 of 1 MGy γ-ray irradiated samples became very small. However, the increase was observed again in the PP samples after 48 h of irradiation by positrons during the PAL experiment. This suggests a restructuring of the short polymer chains cut by γ-ray irradiation may occur.

Pulse height distributions were measured using a CdZnTe detector inside a lead collimator to investigate main source producing high dose rates above the shield plugs of Unit 3 at Fukushima Daiichi Nuclear Power Station. It was confirmed that low energy photons are dominant. Concentrations of Cs-137 under 60 cm concrete of the shield plug were estimated to be between 8.1E+9 and 5.7E+10 Bq/cm2 from the measured peak count rate of 0.662 MeV photons. If Cs-137 was distributed on the surfaces of the gaps with radius 6m and with the averaged concentration of 5 points, 2.6E+10 Bq/cm2 , total amount of Cs-137 is estimated to be 30 PBq.

Pulse height distributions were measured using a LaBr3 detector set in a 1 cm lead collimator to investigate main radiation source at the operation floor of Fukushima Daiichi Nuclear Power Station Unit 4. It was confirmed that main radiation source above the reactor well was Co-60 from the activated steam dryer in the DS pool (Dryer-Separator pool) and that at the standby area was Cs-134 and Cs-137 from contaminated buildings and debris at the lower floor. Full energy peak count rate of Co-60 was reduced about 1/3 by 12mm lead sheet placed on the floor of the fuel handling machine.

The irradiation effects on five kinds of polyethylenes (PEs) were studied from the viewpoints of mechanical properties, free radicals and positron annihilation. The degradation of the mechanical strength of samples irradiated by 60Co γ-rays was evaluated based on the elongation at break and the tensile strength. Fully stretched PE with a crystallinity larger than 99% was greatly affected by γ-irradiation. In low-density PEs free radicals were detectable only above 70 kGy, and sharply increased above 100 kGy. A detectable number of free radicals was obtained even at 0.1 kGy in PEs haaving high crystallinity. At around 100 kGy, the increase in the intensity (I3) of ortho-positronium (o-Ps), seems to be associated with an increase in the mechanical strength. Contrary to the expectation that the o-Ps seeks intermolecular space holes only in amorphous regions, the I3 obtained in PEs with nearly 100% crystallinity was almost half that low-density PEs, and τ3 had similar values. This suggests that even in crystalline regions the o-Ps seeks intermolecular space holes comparable to those in the amorphous regions.

The positron annihilation lifetime method (PAL) has been applied to study the characteristics of polyethylenes (PEs) at low temperatures between 273 and 100 K. It has been found that the intensity (I3) of the long-lived component of positronium (Ps) showed an increase in non-annealed PE and annealed PE in vacuo. However, PAL in PEs annealed in an atmosphere containing oxygen did not show such an increase. It has been indicated that the latter effect is due to formation of carbonyl groups through oxidation during the annealing.

Positron annihilation lifetimes (PAL) have been measured for polythylenes (PEs) under differenr conditions of heat treatment. It is shown that the intensity, I 3 , of the long-lived component of positronium (Ps) shows hystereses between the heating and cooling processes due to aging effect. It is also shown that about half of Ps observed at low temperatures below the glass transition is inhibited after the sample is heat-treated above the melting point in the atmosphere containing oxygen. It is suggested that carbonyl groups (C0) formed by thermal oxidation can inhibit Ps formation through trapping the precursors of Ps, e + and/or e - .

63 Ni (β − decay; t 1 2 = 100.1 y ) is produced abundantly in stainless steel and copper hardware at high-energy accelerators. A measurement method using a liquid-scintillation counter has been developed. Its approximate activity could be estimated based on the thermal and fast-neutron fluxes measured by an activation method using gold and copper. After a few tens of years from beam-off, the existence of a no γ-radiation level from this accelerator hardware does not necessarily mean that all activity has decayed out, since there is still a possibility that an appreciable amount of 63 Ni remains.

Degradation of Gd 2 SiO 5 :Ce in optical transmittance due to proton irradiation was negligibly small below 10 6 rad, smaller than 2%/cm at 10 7 rad and large at 10 8 rad. The radiation hardness of 10 7 rad against protons is by two orders of magnitude smaller than against low energy γ-rays. Long term spontaneous recovery of the proton-induced damage is not large (10–20% of the initial degradation in 84 days). Recovery upon exposure to UV light occurs to some extent. Degradation due to thermal neutrons was negligibly small for a fluence of 10 14 n/cm 2 . No degradation was observed for exposure to fast neutrons of about 10 13 n/cm 2 during one year in the extracted beam tunnel of proton synchrotron.

We compared radiation damages of undoped CsI for 12 GeV protons and for 60Co γ-rays between 104 and 108 rad. Degradation in optical transmission was similar in magnitude both for protons and γ-rays; it is as small as 1–3% per 1 cm thickness at 104 rad, while it is as large as or larger than 5% above 105 rad. The above feature is different for BGO or GSO:Ce, whose radiation hardness is roughly two orders of magnitude smaller regarding protons than regarding γ-rays. Recovery of damage is qualitatively similar both for proton and γ-ray irradiations; spontaneous recovery is only partial and the annealing effect of UV exposure is negligibly small.

The relative abundance of tritiated-airborne species was studied for the air of the beam-line tunnel at high-energy accelerators as well as atmospheric air. The tritium produced via nuclear spallation reactions in the accelerator-tunnel air exists in the chemical forms of HTO and HT. The HT-to-HTO ratio was about 2 × 10 −2 on the average, being appreciably smaller than that in atmospheric air. The reaction mechanisms of accelerator-produced tritiums were discussed on the basis of the similarity to the reactions by cosmic-generated tritium. HT is likely to be formed directly through the reaction of a recoiling tritium with H 2 O. On the other hand, the HT-to-HTO ratio for the present atmospheric air indicates that tritium distributions have been largely modified by the release of man-made tritium into the air.

The polymerization of bisphenol-A epoxy resin mixed with a curing agent (methyltetrahydrophthalic anhydride) was followed from the liquid to the solid state using the positron annihilation lifetime (PAL) technique at several curing temperatures. With the commencement of polymerization, the intensity, I 3 , of ortho -positronium started to increase, followed by a sharp decrease of its lifetime, τ 3 . When the curing temperature was raised further, I 3 increased to a large value, indicating further propagation of the polymer networks. When the polymerization was terminated, τ 3 reached the smallest value and I 3 reached a large saturation value. PAL is a powerful technique for studying microscopic structural changes and state transitions of polymers.

It was indicated that 55 Fe (EC decay, half-life: 2.7 y) is the most abundant radioisotope in the residual activities formed in hardware composed of iron and steel at high energy accelerator facilities. Its approximate activity could be evaluated on the basis of an integrated neutron flux measured by an activation method using a copper threshold detector. Both a low energy photon spectroscopy and a liquid scintillation counting method were confirmed to be applicable to 55 Fe measurement with high sensitivity.

Formation cross sections of product nuclides in the nuclear reactions of Ti, Fe, Co, Ni, Cu, and Zn targets by 500-MeV protons were measured with a Ge(Li) γ-ray spectrometer. The measured cross sections in the mass range between \(A\cong40\) and \(A\cong{A}_{\text{T}}-4\) were used in the charge-dispersion analysis, where A T is the mass number of the target nucleus. The N / Z ratio of the charge-dispersion peak was found to be consistent with those obtained in the same mass range of spallation products in the nuclear reactions of the same medium-mass targets with 12-GeV protons. The mass-yield curve falls sharply with decreasing masses of product nuclides in contrast to relatively flat distributions at higher energies.

Production cross sections of tritium in high energy nuclear reactions with 12 GeV protons were measured for Al, Co, Cu, Nb, Ag, In, Sn, Au and Pb targets. Large production cross sections of > 500 (mb) were obtained for Au and Pb targets. From their atomic weight dependence, tritium cross sections (σ) in mb can be expressed as a function of target atomic weight (A) by the following simple equation: σ(A) = 95 exp(A107), which should be useful for predicting unknown cross sections. Together with other existing data at different energies, the present data suggest that there is no energy dependence of tritium cross section at proton energies above several GeV.

The particle sizes and fuming rates of radioactive nuclides and matrix elements were extensively investigated for aerosols generated by the heat cutting of activated metals. The aerosols showed either lognormal activity or mass distributions with modes at 0.3∼0.5 μm and/or 4∼6 μm. Some carrier-free radioactive nuclides were remarkably enriched in the aerosols, and showed different distribution patterns from matrix metal elements. The results are discussed on the basis of the thermal properties of the radioactive and matrix elements.

Positron irradiation effects on polypropylene (PP) and polyethylene during the positron lifetime measurements have been studied in detail. The effect, which was to decrease I 3 , has been found to be larger in air than in vacuum. For PP, when the lifetime measurements were performed at temperatures above 348K, the radiation effect was scarcely observable. However at low temperature the radiation effect was accumulated and I 3 was decreased during the measurements. Irradiation of Co-60 γ-ray up to the dose of 300 MRad also lead to similar decrease in I 3 , but the decrease due to γ-irradiation was not as large as that due to the positron irradiation. Irradiation effect of positrons appears to be different from that of γ-rays

Water absorption rates of four kinds of epoxy resins cured with phenol novolac (PH) were compared with the results of positron annihilation lifetime measurements (PAL). Three samples: cresol novolac (CR), tetra-methyl-biphenol (TMB) and bis-phenol A (BA), showed almost similar absorption rates, while tris-hydroxy-phenyl-methane (THPM) absorbed water twice as fast as others. Since THPM has a larger τ 3 value (hence larger intermolecular-space holes) than the other samples, the correlation between τ 3 and the absorption rate seems evident. For THPM, the lifetime distribution was shifted toward a shorter lifetime after absorbing water, which is interpreted in terms of the particular structure of three-dimensional holes

We have measured the neutron leakage spectra outside the shielding in the KEK counter hall using a multisphere technique supplemented by the 12C(n, 2n)11C reaction in a carbon activation detector. The neutron spectra were derived from the measurements using the LOUHI78 unfolding code. The shape of these unfolded neutron spectra matched very closely that of spectra calculated by O'Brien and McLaughlin. A comparison of the dose equivalent as derived from the spectra with that measured by a neutron dose equivalent meter confirmed that the dose equivalent meter measurements usually underestimate the dose equivalent by at least 30%.