scholarly journals Laboratory data on atomic spectra for extreme ultra-violet solar spectroscopy

1965 ◽  
Vol 23 ◽  
pp. 25-26 ◽  
Author(s):  
B. Edlén
Keyword(s):  
Relative Abundance ◽  
A Priori ◽  
Laboratory Data ◽  
Solar Spectrum ◽  
Ultra Violet ◽  
Laboratory Work ◽  
Atomic Systems ◽  
The Third ◽  
Order Of Magnitude ◽  
Very High

Expected relative prominence of elements and ionization stages is estimated from existing recordings of the solar XUV spectrum. The following 3 groups of elements, apart from H and He, need be considered : (C, N, O), (Ne, Mg, Si, Fe), (Na, Al, S, Ar, Ca, Ni), the relative abundance descending by approximately an order of magnitude from one group to the next, and all other elements being at least another order of magnitude less abundant. Lines of low and medium stages of ionization are expected only from most abundant elements. The observed presence in the solar spectrum of lines from the neon-like Fe XVII suggests that very high stages of ionization must not be a priori excluded.These considerations indicate that a discussion of laboratory data may be confined to atomic systems containing from 1 to 18 electrons. Observed data on these 18 isoelectronic sequences, and the possibilities of their extrapolation, are reviewed. It is concluded that required data for the first 10 sequences are well in hand, but considerable laboratory work remains to be done on the third-period sequences.A comprehensive paper is being prepared for later publication.

THE EFFECT OF THE ULTRA-VIOLET COMPONENT OF SUNLIGHT ON CERTAIN AQUATIC ORGANISMS

1930 ◽  
Vol 3 (2) ◽  
pp. 104-106 ◽  
Author(s):  
A. Brooker Klugh
Keyword(s):  
Solar Spectrum ◽  
Ultra Violet ◽  
Aquatic Organisms ◽  
Anguilla Rostrata ◽  
Marked Contrast ◽  
The Third ◽  
Ultra Violet Radiation ◽  
Short Time ◽  
Considerable Depth ◽  
Violet Radiation

In these experiments, which are a continuation of work carried out in 1927 and 1928, certain aquatic animals were exposed to sunlight behind filters which transmitted different regions of the solar spectrum. The first filter transmitted both the visible and ultra-violet regions, the second the visible only and the third the ultra-violet only. Young eels, Anguilla rostrata, which are in shallow water when ascending the streams, an Amphipod, Gammarus locusta, which was taken from shallow tide-pools, and a Ctenophore, Bolinopsis infundibulum, which floats about at the surface of the sea, all proved to be very resistant to ultra-violet radiation, thus showing a marked contrast to those animals which remain at some considerable depth in the sea or which come to the surface only when the illumination is very weak, as the latter are killed in a short time by exposure to ultra-violet radiation.

scholarly journals The ultra- violet band of ammonia, and its occurrence the solar spectrum

1918 ◽  
Vol 94 (663) ◽  
pp. 470-471 ◽  
Keyword(s):  
Solar Spectrum ◽  
Ultra Violet ◽  
The Sun ◽  
Third Order ◽  
The Third ◽  
Other Substances ◽  
Violet Band ◽  
Band Spectra ◽  
Concave Grating ◽  
Unusual Appearance

A question of great interest in connection with the solar spectrum is that of the origin of the thousands of unidentified faint lines which were photographed and catalogued by Rowland. Some of these lines may possibly be identical with faint lines in metallic spectra which have not yet been completely tabulated, but in view of the presence of bands of cyanogen, carbon, and hydrocarbon, the possibility of the correspondence of most of them with band spectra of other substances should not be overlooked. As a contribution to this inquiry, the present investigation was undertaken primarily in order to determine whether Group P in the ultra-violet region of the solar spectrum might not be mainly due to the presence of ammonia in the absorbing atmosphere of the sun. Ammonia was already known to give a remarkable band in this region, having its greatest intensity near λ 3360, but existing records of the component lines were inadequate for comparison with the solar tables. Photographs were accordingly taken with instruments of various dispersions, ranging up to that of the third order of a 10 feet concave grating, a copper arc in an atmosphere of ammonia being employed as the source in the latter case. In view of the unusual appearance of the band, an attempt has also been made to elucidate the chief features of its structure.

scholarly journals On the stopping of fast particles and on the creation of positive electrons

1934 ◽  
Vol 146 (856) ◽  
pp. 83-112 ◽  
Keyword(s):  
Quantum Mechanics ◽  
Cross Section ◽  
Nuclear Charge ◽  
Primary Energy ◽  
Stopping Power ◽  
Nuclear Scattering ◽  
The Third ◽  
High Energies ◽  
Order Of Magnitude ◽  
Very High

The stopping power of matter for fast particles is at present believed to be due to three different processes: (1) the ionization; (2) the nuclear scattering; (3) the emission of radiation under the influence of the electric field of a nucleus. The first two processes have been treated in quantum mechanics by Bethe, Møller, and Bloch in a very satisfactory way. A provisional estimation of the order of magnitude to be expected in the third process has been given by Heitler. The result obtained was that the cross-section ϕ for the energy loss by radiation for very fast particles (if the primary energy E 0 ≫ mc 2 ) is of the order ϕ ∽ Z 2 /137 ( e 2 / mc 2 ) 2 , (1) Where Z is the nuclear charge. It is the aim of the present paper to discuss in greater detain the rate of loss of energy by this third process and its dependence on the primary energy; in particular we shall consider the effect of screening . The results obtained for very high energies (> 137 mc 2 ) seem to be in disagreement with experiments made by Anderson ( cf . 7).

Monte Carlo Algorithms for Moments of Transition Arrays

1988 ◽  
Vol 102 ◽  
pp. 79-81
Author(s):  
A. Goldberg ◽  
S.D. Bloom
Keyword(s):  
Monte Carlo ◽  
State Vector ◽  
Basis Vector ◽  
Collective State ◽  
Dispersion Characteristics ◽  
Dipole Strength ◽  
The Third ◽  
Monte Carlo Algorithms ◽  
Third Moment ◽  
Very High

AbstractClosed expressions for the first, second, and (in some cases) the third moment of atomic transition arrays now exist. Recently a method has been developed for getting to very high moments (up to the 12th and beyond) in cases where a “collective” state-vector (i.e. a state-vector containing the entire electric dipole strength) can be created from each eigenstate in the parent configuration. Both of these approaches give exact results. Herein we describe astatistical(or Monte Carlo) approach which requires onlyonerepresentative state-vector |RV> for the entire parent manifold to get estimates of transition moments of high order. The representation is achieved through the random amplitudes associated with each basis vector making up |RV>. This also gives rise to the dispersion characterizing the method, which has been applied to a system (in the M shell) with≈250,000 lines where we have calculated up to the 5th moment. It turns out that the dispersion in the moments decreases with the size of the manifold, making its application to very big systems statistically advantageous. A discussion of the method and these dispersion characteristics will be presented.

La experiencia del prácticum en educación infantil. Una narración en primera persona

2019 ◽  
pp. 60-76
Author(s):  
Victor Amar
Keyword(s):  
Early Childhood ◽  
Teacher Training ◽  
Early Childhood Education ◽  
Professional Growth ◽  
Childhood Education ◽  
The Third ◽  
Formative Experience ◽  
Narrative Methodology ◽  
Very High

The chances of success of the internship in early childhood education, which takes place in the third degree, are very high. However, there may be circumstances that may befall the teacher-training student, which in a way turn the formative experience into a pretext for personal and professional growth. In order to know and understand its practice, we use narrative methodology. It is the most suitable way we have found to share his voice, giving him epistemological authority and being a pretext to improve from his experience. Her words lead us to understand that she wants to be a teacher, and that she learns in any situation, even though her tutor is in a context and with a very particular reality. The conclusion is in continuous construction as the student has learned, disapproved and reappeared with the practice; from being a student of practice to becoming one in practice.

Effect of the Stages of Floral Development and Postharvest Temperatures to Flowering of Eremurus in Israel

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 536d-536
Author(s):  
Rina Kamenetsky
Keyword(s):  
Morphological Analysis ◽  
Developmental Disorder ◽  
Floral Development ◽  
The Third ◽  
Initial Stage ◽  
Floral Differentiation ◽  
Soil Temperatures ◽  
Very High ◽  
Development Application ◽  
Flowering Process

The influence of postharvest temperature on the flowering response of Eremurus was studied. The plants were harvested at four different stages of development and were separated into three groups. The first group was immediately exposed to 2 °C, the second group to 20 °C followed by 2 °C, and the third group to 20 °C followed by 32 °C and, subsequently, 2 °C. Scanning electron microscopy (SEM) was used for concurrent morphological analysis of floral development. Application of 2 °C to the plants in the initial stage of floral development caused plant destruction and death, while the same treatment applied at the stage of full differentiation promoted normal flowering. Temperatures of 20 °C and, especially, 32 °C, significantly improved flowering of the plants harvested in the early stages of florogenesis, whereas the same treatment applied to the plants harvested at the end of flower differentiation did not affect the flowering process. A developmental disorder, which we term “Interrupted Floral Development” (IFD), was observed only in the plants harvested when the racemes were fully differentiated. This was probably caused by the very high air and soil temperatures that prevail in Israel during the summer. The extent of floral differentiation has a determinant role in subsequent scape elongation and flowering.

scholarly journals Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission

Solar Physics ◽  
2021 ◽  
Vol 296 (3) ◽  
Author(s):  
Ryan O. Milligan
Keyword(s):  
Solar Flares ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Solar Limb ◽  
High Background ◽  
Superposed Epoch Analysis ◽  
Lyman Alpha ◽  
Alpha Emission ◽  
Epoch Analysis ◽  
Very High

AbstractAs the Lyman-alpha (Ly$\upalpha $ α ) line of neutral hydrogen is the brightest emission line in the solar spectrum, detecting increases in irradiance due to solar flares at this wavelength can be challenging due to the very high background. Previous studies that have focused on the largest flares have shown that even these extreme cases generate enhancements in Ly$\upalpha $ α of only a few percent above the background. In this study, a superposed-epoch analysis was performed on ≈8500 flares greater than B1 class to determine the contribution that they make to changes in the solar EUV irradiance. Using the peak of the 1 – 8 Å X-ray emission as a fiducial time, the corresponding time series of 3123 B- and 4972 C-class flares observed in Ly$\upalpha $ α emission by the EUV Sensor on the Geostationary Operational Environmental Satellite 15 (GOES-15) were averaged to reduce background fluctuations and improve the flare signal. The summation of these weaker events showed that they produced a 0.1 – 0.3% enhancement to the solar Ly$\upalpha $ α irradiance on average. For comparison, the same technique was applied to 453 M- and 31 X-class flares, which resulted in a 1 – 4% increase in Ly$\upalpha $ α emission. Flares were also averaged with respect to their heliographic angle to investigate any potential center-to-limb variation. For each GOES class, the relative enhancement in Ly$\upalpha $ α at the flare peak was found to diminish for flares that occurred closer to the solar limb due to the opacity of the line and/or foreshortening of the footpoints. One modest event included in the study, a C6.6 flare, exhibited an unusually high increase in Ly$\upalpha $ α of 7% that may have been attributed to a failed filament eruption. Increases of this magnitude have hitherto only been associated with a small number of X-class flares.

scholarly journals Statistical Uncertainty of DNS in Geometries without Homogeneous Directions

2021 ◽  
Vol 11 (4) ◽  
pp. 1399
Author(s):  
Jure Oder ◽  
Cédric Flageul ◽  
Iztok Tiselj
Keyword(s):  
Channel Flow ◽  
A Priori ◽  
Time Integration ◽  
Navier Stokes ◽  
Statistical Uncertainty ◽  
Time Step ◽  
Order Of Magnitude ◽  
Averaging Time ◽  
The Individual ◽  
Time Required

In this paper, we present uncertainties of statistical quantities of direct numerical simulations (DNS) with small numerical errors. The uncertainties are analysed for channel flow and a flow separation case in a confined backward facing step (BFS) geometry. The infinite channel flow case has two homogeneous directions and this is usually exploited to speed-up the convergence of the results. As we show, such a procedure reduces statistical uncertainties of the results by up to an order of magnitude. This effect is strongest in the near wall regions. In the case of flow over a confined BFS, there are no such directions and thus very long integration times are required. The individual statistical quantities converge with the square root of time integration so, in order to improve the uncertainty by a factor of two, the simulation has to be prolonged by a factor of four. We provide an estimator that can be used to evaluate a priori the DNS relative statistical uncertainties from results obtained with a Reynolds Averaged Navier Stokes simulation. In the DNS, the estimator can be used to predict the averaging time and with it the simulation time required to achieve a certain relative statistical uncertainty of results. For accurate evaluation of averages and their uncertainties, it is not required to use every time step of the DNS. We observe that statistical uncertainty of the results is uninfluenced by reducing the number of samples to the point where the period between two consecutive samples measured in Courant–Friedrichss–Levy (CFL) condition units is below one. Nevertheless, crossing this limit, the estimates of uncertainties start to exhibit significant growth.

scholarly journals Observational manifestations of ‘cosmological dinosaurs’ at redshifts z ∼ 20

2021 ◽  
Vol 503 (2) ◽  
pp. 3081-3088
Author(s):  
V K Dubrovich ◽  
Yu N Eroshenko ◽  
S I Grachev
Keyword(s):  
Black Hole ◽  
Atomic Hydrogen ◽  
Radiation Transfer ◽  
Ring Width ◽  
High Mass ◽  
Primordial Black Hole ◽  
Array Type ◽  
Local Sources ◽  
Order Of Magnitude ◽  
Very High

ABSTRACT We consider a primordial black hole of very high mass, $10^9\!-\!10^{10}\, \mathrm{M}_\odot$, surrounded by the dark matter and bayonic halo at redshifts z ∼ 20 without any local sources of energy release. Such heavy and concentrated objects in the early Universe were previously called ‘cosmological dinosaurs’. Spectral distribution and spatial variation of the brightness in the 21-cm line of atomic hydrogen are calculated with the theory of radiation transfer. It is shown that a narrow and deep absorption arises in the form of the spherical shell around the primordial black hole at the certain radius. The parameters of this shell depend almost exclusively on the mass of the black hole. The angular diameter 18 arcsec of the absorption ring at z ∼ 20 is well within the current technical possibilities of the Square Kilometre Array type telescopes. But the observation of the ring width itself requires an order of magnitude better resolution.

scholarly journals Ultra-violet transparency of the lower atmosphere, and relative poverty in Ozone

1918 ◽  
Vol 94 (660) ◽  
pp. 260-268 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Solar Spectrum ◽  
Ultra Violet ◽  
Lower Atmosphere ◽  
Atmospheric Ozone ◽  
Absorption Bands ◽  
Relative Poverty ◽  
Narrow Bands

Many years ago it was suggested by Hartley* that the limit of the solar spectrum towards the ultra-violet was attributable to absorption by atmospheric ozone, which, as he showed, would give rise to a general absorption beginning at about the place where the solar spectrum ends. In a recent paper by Prof. A. Fowler and myself,† the evidence for this view was very much strengthened. For it was shown that just on the limits of extinction the solar spectrum shows a series of narrow absorption bands which are eventually merged in the general absorption, and these narrow bands are precisely reproduced in the absorption spectrum of ozone. For my own part, I do not feel any doubt that ozone in the atmosphere is the effective cause limiting the solar spectrum.

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