Elemental mass distribution

Aerosol was occasionally sampled with low pressure impactors (LPI s) to obtain sulfur and elemental mass distributions using the techniques described by Ouimette (13). 

Elemental mass distribution - The aerosol sampled by the LPI for elemental analysis was impacted on coated mylar films affixed to 25 mm glass discs. The mylar had been coated with Apiezon L vacuum grease to prevent particle bound. The LPI samples were sent to Crocker Nuclear Laboratory for elemental analysis by PIXE using a focused alpha particle beam of 3 to 4 mm diameter. Nanogram sensitivities for most elements were achieved with the focused beam. A detailed description of the PIXE focused beam technique applied to LPI samples can be found in Ouimette (13). Based upon repeated measurements of field samples, the estimated measurement error was about 15-20% or twice the minimum detection limit, whichever was larger. 

Elemental mass distributions were measured using the LPI-PIXE technique on September 7, 1979. A cyclone preseparator upstream of the LPI removed coarse aerosol. Some of the results are presented in Figures 6a-c. The concentration of... 

A new model for heat-up of structures due to radioactive decay heating caused by deposited fission products has been included in VICTORIA-92. Decay heating is calculated according to elemental mass distribution and time since reactor shutdown. Temperatures of the deposited film and structure are calculated. Radioactive decay heating can cause deposited materials to revaporize and migrate through the RCS. This process can affect the source term late in an accident sequence when the containment is likely to have failed. In some cases, decay heating may induce failure of the RCS. 

Derivation of the formula for the attraction field caused by an infinitely thin line with the density X is very simple, and is illustrated in Fig. 4.5b. We will consider the field at the plane y = 0. Due to the symmetry of the mass distribution, we can always find a pair of elementary masses Xdy and —Xdy, which when summed do not create the field component gy directed along the y-axis, and respectively the total field generated by all elements of the line has only the component located in the plane y — 0. Here r is the coordinate of the cylindrical system with its origin at the point 0, and the line with masses is directed along its axis. As is seen from Fig. 4.5b the component dg at the point located at the distance r from the origin 0 is... 

The epoch and mode of galaxy formation are not well known, but both quasars and star-forming galaxies are known with redshifts up to about 7, corresponding to an era when the expanding Universe was only 1/8 of its present size, and the emission-line spectra of quasars indicate a large heavy-element abundance (solar or more Hamann Ferland 1999), suggesting prior stellar activity. The first stars, on the other hand, known as Population IIP, would have been devoid of metals whether they differed from normal stars in other basic characteristics, notably their mass distribution, is not known, since no completely metal-free stars have been... 

In qualitative terms, microscopic interactions are caused by differences in crystal chemical properties of trace element and carrier, such as ionic radius, formal charge, or polarizability. This type of reasoning led Onuma et al. (1968) to construct semilogarithmic plots of conventional mass distribution coefficients K of various trace elements in mineral/melt pairs against the ionic radius of the trace element in the appropriate coordination state with the ligands. An example of such diagrams is shown in figure 10.6. 

In a search for sources of alkaline materials in rural air and rain, we have sampled and performed multi-element analyses on ambient particulate matter and potential source materials. Ambient aerosols were sampled daily using single Nuclepore filters or Florida State University "streakers." Samples of soil and unpaved road materials were also collected and analyzed. The samples were analyzed by various multi-element methods, including ion-and proton-induced X-ray emission and X-ray fluorescence, as well as by atomic absorption spectrophotometry. Visual observations, as well as airborne elemental concentration distributions with wind direction and elemental abundances in aerosols and source materials, suggested that soil and road dust both contribute to airborne Ca. Factor analysis was able to identify only a "crustal" source, but a simple mass balance suggested that roads are the major source of Ca in rural central Illinois in summer. 

There are several bodies of information that feed into our understanding of stellar nucleosynthesis. We will start with a discussion of the classification of stars, their masses and mass distributions, and their lifetimes. From this information we can assess the relative importance of different types of stars to the nucleosynthesis of the elements in our solar system and in the galaxy. We will then discuss the life cycles of stars to give a framework for the discussion of nucleosynthesis processes. Next, we will review the nuclear pathways... 

These observations would give important constraints on the distribution of the heavy elements and 56Co in the ejecta. We adopted the hydrodynamical model 11E1Y6 (Nomoto et al. 1988) and carried out Monte Carlo simulation for photon transfer. A step-like distribution of 56Co was assumed where the mass fraction of 56Co in the layers at Mr < 4.6 Mq, 4.6 - 6 M , 6-8 Mq, and 8-10 Mq are Xq0 = 0.0128, 0.0035, 0.0021, and 0.0011, respectively. Other heavy elements were distributed with mass fractions in proportion to 56Co. 

Recall that X rays are diffracted by the electrons that surround atoms, and that images obtained from X-ray diffraction show the surface of the electron clouds that surround molecules. Recall also that the X-ray diffracting power of elements in a sample increases with increasing atomic number. Neutrons are diffracted by nuclei, not by electrons. Thus a density map computed from neutron diffraction data is not an electon-density map, but instead a map of nuclear mass distribution, a "nucleon-density map" of the molecule (nucleons are the protons and neutrons in atomic nuclei). 

Murphy, D.M., Garbarino, J.R., Taylor, H.E., Hart, B.T. and Beckett, R. (1993) Determination of size and element composition distributions of complex colloids by sedimentation field-flow fractionation-inductively coupled plasma mass spectrometry. /. Chromatogr., 642, 459M67. 

Figure 1.65 CFD simulations giving 3-D mass contour plots in the cross-channel structure for a design without and one with two static mixing elements. The completeness of mixing can be judged from the cross-sectional mass distribution at the outlet [71] (by courtesy of Elsevier Ltd.).

Figure 1. Cumulative mass distributions of the element A1 plotted using impactor D50 values and mmads derived from scanning electron microscope analyses. The impactor was run down-stream from an electrostatic precipitator with uncoated impaction stages. Reproduced with permission from Ref. 15. Copyright 1978, Pergamon Press Ltd.

Elemental mapping to depict distributions of elements over the mass distribution image or a secondary electron image... 

The trace element distributions of uninvolved psoriatic skin merit special comments. The main Fe peak appears closer to the mass distribution peak than in normal skin. Also, there are obvious variations in the Fe content in different strata (cell layers), and the lowermost values are consistently at least twice as high as those in normal skin. Our PIXE investigation substantiates the previously reported finding that psoriatic patients lose Fe through the shedding of stratum corneum cells in lesional areas by demonstrating that clinically normal skin of psoriatic patients contains higher than normal amounts of Fe.36,37... 

In comparison to the control skin there are high mean values and prominent variations in the trace elements, notably Fe and Zn, in the upper level of the epidermis. However, the mass distribution pattern essentially follows that of normal control skin with some variations in the upper layer. 

A distribution in more than one variable may be illustrated by the function describing the distribution of matter in a sphere with its center at the origin of a cartesian system. If the radius is c and density p, then the distribution of matter Pix y z) is a function of three variables with the definition that P Xjy,z) dx dy dz is the amount of matter in the element of volume bounded by the set of six cartesian planes through the points x,y,z) and (x + dx, y + dy, z + dz). The mass-distribution function P x,yyZ) is then equal to the density p, for all points satisfying the condition x + / + 2 c. If we are interested in the distribution of matter in only two dimensions, we can obtain a function P(x,y) from P(x,yjz) by integrating over all z ... 

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