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The term “ionospheric sluggishness” is used to describe the time delay between maximum radio absorption in the ionosphere following the time of maximum irradiance during a solar flare. Sluggishness...

Hot Mix Asphalt (HMA) is used in the construction of highway roads, parking lots and other pavement repairs in the US and worldwide. During asphalt pavement installation, a large amount of asphalt fume containing volatile organic compounds (VOCs) is emitted, causing potential health risks to construction workers. The field data investigation in this paper reports the concentration of VOCs around the workers on site using the Photo Ionization Detection (PID) device. Additionally, this paper presents a health risk evaluation model based on the Monte Carlo simulation to assess the carcinogenic and non-carcinogenic risks of workers during pavement construction. More specifically, distribution and sensitivity analyses illustrate the factors that pose the greatest health risks caused by certain VOCs. The study calls for better health risk controls by targeting the emission sources, propagating pathways, and individual receptors of the VOCs to protect workers’ health during pavement construction. This paper contributes to the knowledge of VOCs generated from HMA and the potential health risks to construction workers, as well as suggests the implementation of new requirements for pavement construction codes and safety regulations.

We summarize the goals of photo-ionization modelling of nebulae ionized by Wolf-Rayet stars and discuss the methodology. We present some examples in different astrophysical contexts: ring nebulae around massive WR stars, planetary nebulae with [WR]-type central stars, and giant H II regions with WR stars. We discuss in more detail a work in progress (Stasińska & Schaerer 1999) on the galaxy I Zw 18.

We calculate the photo-ionization cross-section from the ground state of the helium atom, using the complex rotation method and diagonalization of sparse matrices. This produces directly the positions and widths of the doubly excited 1Po resonances together with the photo-ionization cross-section. Our calculations up to the N=9 threshold are in perfect agreement with recent experimental data and show the transition from a regular structure at low energy to a chaotic one at high energy, where various resonances strongly overlap., Revtex 6 pages 4 figures

We present an analysis of the UV spectra of the fast ONeMg nova V693 Coronae Austrinae 1981. Observations with IUE began on 1981 April 10 and continued until 1981 November 14. We find the reddening for the nova to be E (B V) ~0.2 ± 0.1. Using the photo ionization code CLOUDY 90.02 and the minimization routine MlNUIT, we derive elemental abundances for the ejecta. We find the following abundances, relative to solar material: He=1.3, C=2.S, N=132, 0=14, Ne=247, Mg=7.9, AI = 60 and Si = 22. These results are based on independent fits to three different dates of observation, spanning six months. We find a high N/O ratio which is indicative of an outburst on a massive white dwarf.

Scattering o f small potassium clusters by water molecules has been studied in a molecular beam experiment for the first time. In the size range up to eight atom s, trends for cross sections have been obtained by investigating low energy collisions. Significant differences in relative cross sections can be assigned to inelastic collisions. As in case o f scattering o f sodium clusters by argon (Goerke, A. et al., J. Chem. Phys. 98, 9653 (1993)), rotational excitation of the clusters seems to be the dominating interaction.

Determining the masses of the central compact object believed to power all active galactic nuclei is relevant to our understanding of their evolution and of their inner workings. Keys to present-day mass estimates are: (1) the assumption of line broadening due to virial motion of the emitting gas, (2) an estimate of the distance of broad-line emitting gas from the central compact object, and (3) a measure of the AGN luminosity. We discuss the merits and the limitations of an alternative method based on estimates of physical conditions in the broad line emitting region derived from an appropriate multi-component analysis of emission line profiles. This ‘photo-ionization method’, applied to UV intermediate-ionization lines appears to be promising for at least a sizable population of high-z quasars.

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2 . We also test reasonable parameter changes of the photo-ionization model. We find that photo- ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in nitrogen with high purity, but not in air., 12 figures

Formaldehyde was the first air pollutant, which already in the 1970s emerged as a specifically non-industrial indoor air quality problem. Yet formaldehyde remained an indoor air quality issue and the formaldehyde level in residential indoor air is among the highest of any indoor air contaminant. Formaldehyde concentrations in 4 different indoor settings (schools, office buildings, new dwellings and occupied dwellings) in Portugal were measured using Photo Ionization Detection (PID) equipment (11,7 eV lamps). All the settings presented results higher than the reference value proposed by Portuguese legislation. Furthermore, occupied dwellings showed 3 units with results above the reference. We could conclude that formaldehyde presence is a reality in monitored indoor settings. Concentration levels are higher than the Portuguese reference value for indoor settings and these can indicate health problems for occupants.

Positive streamers are thought to propagate by photo-ionization whose parameters depend on the nitrogen:oxygen ratio. Therefore we study streamers in nitrogen with 20%, 0.2% and 0.01% oxygen and in pure nitrogen, as well as in pure oxygen and argon. Our new experimental set-up guarantees contamination of the pure gases to be well below 1 ppm. Streamers in oxygen are difficult to measure as they emit considerably less light in the sensitivity range of our fast ICCD camera than the other gasses. Streamers in pure nitrogen and in all nitrogen/oxygen mixtures look generally similar, but become somewhat thinner and branch more with decreasing oxygen content. In pure nitrogen the streamers can branch so much that they resemble feathers. This feature is even more pronounced in pure argon, with approximately 10^2 hair tips/cm^3 in the feathers at 200 mbar; this density could be interpreted as the free electron density creating avalanches towards the streamer stem. It is remarkable that the streamer velocity is essentially the same for similar voltage and pressure in all nitrogen/oxygen mixtures as well as in pure nitrogen, while the oxygen concentration and therefore the photo-ionization lengths vary by more than five orders of magnitude. Streamers in argon have essentially the same velocity as well. The physical similarity of streamers at different pressures is confirmed in all gases; the minimal diameters are smaller than in earlier measurements., Comment: 28 pages, 14 figures. Major differences with v1: - appendix and spectra removed - subsection regarding effects of repetition frequency added - many more smaller changes

Radiative cooling is central to a wide range of astrophysical problems. Despite its importance, cooling rates are generally computed using very restrictive assumptions, such as collisional ionization equilibrium and solar relative abundances. We simultaneously relax both assumptions and investigate the effects of photo-ionization of heavy elements by the meta-galactic UV/X-ray background and of variations in relative abundances on the cooling rates of optically thin gas in ionization equilibrium. We find that photo-ionization by the meta-galactic background radiation reduces the net cooling rates by up to an order of magnitude for gas densities and temperatures typical of the shock-heated intergalactic medium and proto-galaxies. In addition, photo-ionization changes the relative contributions of different elements to the cooling rates. We conclude that photo-ionization by the ionizing background and heavy elements both need to be taken into account in order for the cooling rates to be correct to order of magnitude. Moreover, if the rates need to be known to better than a factor of a few, then departures of the relative abundances from solar need to be taken into account. We propose a method to compute cooling rates on an element-by-element basis by interpolating pre-computed tables that take photo-ionization into account. We provide such tables for a popular model of the evolving UV/X-ray background radiation, computed using the photo-ionization package CLOUDY., 10 pages, 6 figures, Accepted for publication in MNRAS. One figure added and minor textual changes made to first version. Downloadable tables and videos available at http://www.strw.leidenuniv.nl/WSS08/

Multiple ionization and fragmentation of N2 induced by absorption of few photons (44 and 46 eV) has been explored in pump-probe measurements at the free electron laser FLASH [1] at Hamburg. Photo ionization of aligned N2+ ions, produced by photon absorption in sequential steps, is explored and few-photon absorption pathways are traced by inspecting the kinetic energy releases (KER) and the fragment-ion angular distributions as function of the pump-probe delay time.

We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hβ), Ne, EW(Hβ), and the ratios of I(λ 5007), I(λ 4363), I(λ 3727), I(λ 6300), I(λ 6720) and I(λ 4686) relative to I(Hβ). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z = 0.10Z⊙) cannot reproduce the observed features of the spectrum, and that the disagreement can be satisfactorily overcome by allowing for spatial temperature fluctuations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ≃ 0.25 Z⊙ is in better agreement with the observational data than the usually adopted value Z≃0.10Z⊙. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster.

A summary is given of the results of experimental determinations of the atomic photo-ionization cross-sections of the alkali metals. Detailed calculations on sodium are described, using Hartree-Fock wave functions, and it is shown that the theory is capable of reproducing the main features of the experimental results. A comparison with line-strength calculations is made, and the applicability of sum-rule tests is discussed. The finite minimum which is found experimentally in the cross-sections of certain of the alkali metals is attributed to spin-orbit perturbations of the free-electron wave functions. For caesium and rubidium the theoretical calculation based on this effect is shown to give minima of a magnitude comparable to those of the experimental results. The accuracy of previous calculations on the cross-sections of Ca ll is discussed, use being made of sum-rule tests.

The absorption of radiation of wave-length between 230 and 800 Å in neon was measured photometrically in a grazing incidence vacuum spectrograph. For wave-lengths longer than that corresponding to the first ionization limit the absorption coefficients were found to be zero except for photo-excitation of resonance transitions. Two sharp absorption edges were observed at 575 and 256 Å corresponding to the L 3 - and L 1 -edges respectively with a flat maximum between them. The photo-ionization cross-section at the first ionization limit was found to be 5⋅4 x 10 -18 cm 2 independent of the pressure between 50 and 500 μ ; this should be compared with the theoretical value of 5⋅8 x 10 -18 cm 2 obtained by Seaton using a dipole-length approximation. Between 575 and 400 Å the calculated and experimental curves agreed closely within the limits of measurement.

The photo-ionization of atomic potassium is investigated using quantal methods. Emphasis is laid on the great sensitivity of the cross-section to the wave functions employed. The general features of the cross-section as revealed by the laboratory measurement can be understood. To explain the finite minimum observed in the cross-section-frequency curve it is necessary to take into account non-separability effects.

A quantitative theoretical investigation is made of the role of photo-ionization of the gas in the development of ionization currents in gases under uniform fields. Using published values of the relevant absorption coefficients and atomic cross-sections, the theory is applied to the case of air, and the results then compared with those previously obtained experimentally, It is shown that photo-ionization can lead to electrical breakdown only under certain restricted conditions, which relate the ionization coefficients and atomic cross-sections for photon-molecule interaction; these restrictions are such that there must be considerable penetration of the gas by ionizing photons, and in many cases a high proportion of all the photons thus reach the cathode. It is also found that the theoretical curve for the growth of current, obtained on the assumption that photo-ionization is the only operative secondary ionization process, has the same general form as the growth curve based on the other secondary processes, e. g. secondary emission from the cathode; there are, however, significant differences in detail. This quantitative investigation supports the view that photo-ionization does not play a predominant role as a secondary ionization process leading to the electrical breakdown of air at values of p x d ~ 760 cm mm Hg in uniform fields.

芳香族化合物,主としてアニリン,フェノ,.一.ル,フxニレンジアミン,ヒドロキノンなどのベンゼン置換体の溶液中における紫外線照射によってどのような反応が起こるかについて調べた。反応は主として光イオン化(電子放出)または電子移動と,側鎖のβ一結合開裂との二つである。前者についてはさらに,電子受容性の分子(アクセプター)の存在するときとしないときで,それぞれ異なる挙動を示す。すなわち,近くにアクセプターの存在しないときは光イオン化は二段階一二光子過程で起こり,アクセプター渉存在するときは,電荷移動吸収または励起後の電荷移動により一光子的に電子が移ることが確かめられた。低温マトリヅクス申で放出された電子の物理的,化学的挙動についても,主としてN,N',N',N'一テトラメチル-p一フェニレンジアミンについてくわし,い研究を行なった◇つぎに多くの他のベンゼン置換体について光照射の結果,生ずる不安定状態の電子スペクトルをくわしく研究し,T'←T吸収帯(三重項からの吸収帯),カチオン,およびラジカルの吸収帯などをそれぞれ確認した。こうして,種々のベンゼン置換体においてある場合は光イオン化が優先し,ある場合はβ-開裂が優先することを見いだし,その原因について考察した。また,一見異なる分子種がよく類似したスペクトルを与えることを指摘し,これについても考察した。

Photoionization cross-sections are calculated for a number of molecules, using a plane wave method. Agreement with experimental data is considerably improved with respect to common plane wave results if the energy of the photoelectron is assumed to equal the incident photon energy.

金沢大学医薬保健研究域薬学系, By adopting a rapid and sensitive method for simultaneous detection of nivalenol (NIV), deoxynivalenol (DON), fusarenon-X (FX), 3-acetyl deoxinivalenol (3ADON), HT-2 toxin (HT-2), T-2 toxin (T-2) and zearalenone (ZEN), the natural occurrence of these mycotoxins in biscuits made of wheat (201 samples) in Japan was surveyed. Samples were analyzed by LC/MS with atmospheric pressure photo ionization (APPI). Further confirmation was performed by liquid chromatography/time of flight mass spectrometry (LC/TOFMS). The average contamination of each Fusarium mycotoxin was 3.1, 23, 0.7, 0.1 and 4.2 ng/g for NIV, DON, HT-2, T-2 and ZEN, respectively. Multiple toxins were observed in 120 samples while FX and 3ADON were not detected. The incidence of these toxins was 41% for NIV, 98% for DON, 19% for HT-2, 11% for T-2 and 2% for ZEN. There were no significant differences in the concentration and incidence between conventional biscuits made of wheat and biscuits made of wheat for infants. This is the first report concerning the presence of NIV, DON, HT-2, T-2 and ZEN in biscuits in Japan. © 2010 The Pharmaceutical Society of Japan.

THE problem of interpreting the differences between ionization potentials obtained by electron (E.I.) and by photon impact (P.I.) has led us to a careful examination of the structures occurring in the photo-ionization yield curves of cis and trans dichloro- and dibromoethylenes1–3. The regularly spaced structures found in these curves have been interpreted in terms of vibrational progressions involving the C—C valence vibrations of the ions.

PHOTO-IONIZATION in hydrocarbon glasses has been reported for amines1,2 which are known to possess low ionization potentials. In these cases, photo-ionization is proportional to the intensity of the photolysing light. Photo-ionization has been established by observing one or more of the following: absorption spectra of ions and/or electrons1–3; delayed luminescence4; thermoluminescence3,5; electron spin resonance spectra of electrons5; optical bleaching of electrons and the resulting luminescence5; photoconductivity6.

ALTHOUGH many theoretical calculations of the photo-ionization cross-section of atomic hydrogen have been performed (see review by Bates1), no experimental determination of this quantity has previously been made. An experiment is being carried out here which has yielded a value for the photo-ionization cross-section of atomic hydrogen at 850.6 A.

The atomic absorption cross section of calcium has been measured from 1750 to 2028 A at a bandwidth of 0.075 A using photoelectric techniques. Absolute cross sections are presented in four figures and compared with results obtained in other laboratories. (Author)